[HN Gopher] How a heat pump works
___________________________________________________________________
How a heat pump works
Author : WatchdogReset
Score : 191 points
Date : 2023-02-10 13:31 UTC (9 hours ago)
(HTM) web link (hvac-learning.com)
(TXT) w3m dump (hvac-learning.com)
| mastermedo wrote:
| I'm getting an error when trying to load the page: > Error
| establishing a database connection
|
| https://web.archive.org/web/20230210134443/https://hvac-lear...
|
| The archive.org is pretty slow on this one as well, as it is an
| interactive site.
| WatchdogReset wrote:
| The website is new and not fit yet for such numbers of visit,
| so sometimes it does not render well pages. I(admin) still in
| the process of understanding how to build a nice website. I
| will analyze what happened and enhance it. I'm sorry for the
| inconvenience !
| Neil44 wrote:
| OOM Killer strikes again - it always loves mysqld for some
| reason...
| WatchdogReset wrote:
| If you have advice for me, I'll take it ;) can exchange with
| HVAC courses
| chem83 wrote:
| I've had Mitsubishi heat pumps in a condo in the northeast for 3
| years and they've worked great. No other heating sources here. I
| keep them on all day, which the mfgt discourages. My main gripe
| was their kumo cloud and Wi-Fi connectivity but they've since
| fixed firmware and the cloud side and it works much better.
| [deleted]
| boringg wrote:
| Oh I have a question for the community here about heat pumps. I
| have three mini splits that I use for AC but connecting them to a
| home hub is bananas amount of work and inconsistent (Mitsubishi
| brand). I wish there was a legitimately good, robust system to
| connect AC units to my smart thermostat (Ecobee) or even some of
| the other devices I have.
|
| It still feels the wild west for home energy systems - and the
| costs are quite high for the value they provide.
| mataug wrote:
| So far I've been happy with using the mysa ecosystem for my
| smart home. It works with Apple HomeKit, its had relatively
| good reliability and the team behind the product have been
| responsive when I do face issues.
|
| https://shop-us.getmysa.com/products/mysa-ac
|
| From a technical perspective its just a IR remote with a wifi
| connection and a touch UI, but for controlling mini-splits it
| works great in my home.
| yreg wrote:
| Technology Connections has a good video on heat pumps. (Actually
| several of them, I link the newest one.)
|
| https://www.youtube.com/watch?v=MFEHFsO-XSI
| pkulak wrote:
| I just found this guy too. He answered a lot of questions I had
| about efficiency and use below freezing.
|
| https://youtu.be/fxEqVuiHhM0
| ASalazarMX wrote:
| Can't recommend this channel enough, it's like the Captain
| Disillusion of home appliances. The video about hurricane
| lamps was the first I saw, and it solved questions I didn't
| know I had about their weird shapes.
| barbazoo wrote:
| Their main channel is http://youtube.com/user/matthiaswandel
| kenmacd wrote:
| I like his videos, but I don't trust his numbers in this one.
| He shows a COP of ~1 when it's 10 degrees out. These are the
| easiest possible conditions for the HP, and where all the
| specs show the highest COP. His graph showing the HP is
| running equal to a baseboard heater seems very suspect.
| pkulak wrote:
| Are you thinking 10 degrees Celsius? I think all his
| numbers are Fahrenheit.
| kenmacd wrote:
| He's located in NB, so I assumed it was Celsius. To check
| I just compared them to the Environment Canada data it
| seems to match pretty close for NB in Celsius.
| jeffalyanak wrote:
| Edit: nevermind, thought this was still about Technology
| Connections.
| pkulak wrote:
| Ah, yeah. I thought I saw some "60s" and so forth on one
| of the graphs, but I may have read it wrong in the
| moment.
| generaltsos wrote:
| That channel is fascinating. They have created some incredibly
| interesting projects.
| manigandham wrote:
| What have they created? You might be thinking of Tech
| Ingredients - https://www.youtube.com/@TechIngredients
| generaltsos wrote:
| You're spot on - I am subscribed to both so I confused them
| without opening any links. Technology Connections is
| fascinating in its own right as well.
| Casteil wrote:
| He does, but he omits a lot of important considerations that
| make heat pumps impractical for normal Americans.
|
| If he touches on them, it's briefly - if at all, e.g.:
|
| - More expensive units, and more expensive to run power wise.
| It's always difficult to get adoption of new technology that's
| "better" but more expensive to buy & repair - to the point
| where RoI may never happen.
|
| - Power grid implications during very low/record low temps e.g.
| shortages/blackouts, likely worse than those in summer if heat
| pump uptake is widespread.
|
| - With a heat pump, you -need- an alternative source of heat -
| since some days when it's particularly cold, they just won't
| work, or work very inefficiently. Plus, if the power goes
| out... you're definitely not powering a whole house heat pump
| with a small generator like you could a natural gas furnace.
|
| Edit: FWIW, I'd researched this topic heavily & seriously
| considered getting a heat pump to pair with a solar power
| setup. For a number of reasons (chief among them: no return on
| investment before the end of the heat pump's expected service
| life), I will not be getting a heat pump any time soon. That
| may change if prices drop dramatically, but that seems unlikely
| given their increased mechanical/electrical complexity.
| nly wrote:
| - Better than resistive electric heating for the grid. Gas is
| going away so this is a problem that has to be solved anyway.
|
| - Economies or scale will solve the repair and maintenance
| burden... hell, it's not like a gas boiler is maintenance
| free...fucking things requiring serving every year and break
| down all the time in the UK.
|
| - almost noone has a generator when the power goes out
| anyway. This is a very wealthy American perspective.
| Casteil wrote:
| - Sure, at least when it's not super cold. Electrical grid
| may be a "problem that has to be solved" but it's one that
| carries staggering price tags and will have to be gradually
| transitioned into over decades. Natural gas will likely
| still be used as a heat source for many well into the late
| this century if not longer.
|
| - Gas boilers are far simpler units. Less moving parts,
| simpler electronics, all in all fewer points of failure
| than a cutting edge heat pump that can actually produce
| heat when it's below 20f (-7c, i.e. the only kind of
| heatpump that might stand a chance at heating throughout
| the cold winters most of the northern US gets).
|
| - Be that as it may, heat pumps at this time are cost
| prohibitive - making them largely something only "wealthy
| Americans" can afford. Many people still run old 80%
| efficiency units because of similar reasons to boilers:
| they're cheaper, simpler, and less likely to fail.
| rgmerk wrote:
| 88% of US households already have heat pumps, and 66% of
| households have centralised heat pump systems - otherwise
| known as air conditioning.
|
| If you can afford to have them just for cooling, you can
| afford to have them for heating as well; in fact, the
| capital cost may well be lower if people just used their
| air conditioning systems to heat as well.
|
| The same goes for reliability - we manage to make air
| conditioning acceptably reliable and the tech is
| basically the same.
| gambiting wrote:
| >> all in all fewer points of failure than a cutting edge
| heat pump that can actually produce heat when it's below
| 20f (-7c, i.e. the only kind of heatpump that might stand
| a chance at heating throughout the cold winters most of
| the northern US gets).
|
| My family has one in Poland, it was -20C this winter
| already and it worked absolutely fine. It's some cheap
| unit, wouldn't call it "cutting edge". I think there's a
| simple resistive heater that de-ices the fins at low
| temps, but it kept the interior of the house at a (very
| toasty) 24C pretty much non stop even in those low
| temperatures. I have no idea why people keep saying heat
| pumps don't work in low temps. I had a basic split unit
| fitted to my home in UK, literally a basic PS600 midea
| unit and apparently it should work down to -25C without
| any problem.
|
| >>Gas boilers are far simpler units. Less moving parts,
| simpler electronics
|
| Have you ever looked inside a modern gas boiler??? I hard
| disagree that it has less parts than a modern heat pump.
| A heat pump is like your fridge - there's an inverter,
| compressor, and a whole bunch of fins, that's about it. A
| gas boiler has multiple tanks, burn chamber, exhaust
| recirculation, at least 5-6 probes to measure every part
| of the process(and they all can fail in surprising ways
| that renders your boiler dead).
| mikeyouse wrote:
| Only a vanishingly small section of the country has
| design temps below 0o, and even less have design temps
| below -10o (https://cdn-codes-
| pdf.iccsafe.org/bundles/document/new_docum...). Places
| like Boston that seem cold have design temps of 10o,
| Chicago is at 2o, Portland, Maine at 1o, etc. etc.
| (https://codes.iccsafe.org/content/IPC2018/appendix-d-
| degree-...)
|
| A solution doesn't work in 100% of areas can still be the
| best one in the 95% of the places that do make sense!
|
| And to your cost concerns, there's a bunch of Federal
| money (being deployed by the states) in the IRA to
| specifically pay for low-income Heat Pump upgrades.
| flemhans wrote:
| Funny you think it's a wealthy American perspective to have
| a generator for outages. My thoughts went in directions of
| wealthy people in Bangladesh or India.
| ryantgtg wrote:
| Just to soften a few of your confident declarations.
|
| > normal Americans
|
| Please revise this phrase. America consists of many different
| climates and it's very unclear what you mean or why you chose
| the word "normal."
|
| > More expensive to run power wise
|
| You're comparing new gas HVAC vs new heat pump. However,
| don't forget about all the folks that are purchasing a heat
| pump to replace an existing gas unit! For example, my gas
| unit (Goodman unit used in California) is old and not even
| energy star compliant! A new heat pump will be more
| efficient.
|
| > With a heat pump, you -need- an alternative source of heat
|
| By 'you' are you referring to me (or, say, the ~7% of the US
| population that lives in my small area of the country)? If
| so, that's not true! It doesn't get too cold here. And I
| reckon there are quite a few areas in this country where it
| doesn't get cold enough for a heat pump to eat shit.
|
| When you refer to prices and returns on investment, are you
| using a unit + professional installation cost (like $18k+ or
| something)? Or the unit itself (~$4.5k) plus perhaps a DIY
| installation costs (~$1.5-2k)? There is a big range there in
| costs, and the ROI is dependent on that.
| photon12 wrote:
| I put in a new Mitsubishi Hyper-Heat heat pump last summer.
| It got down to 17 Farenheit in Seattle this winter. There
| are no heat strips or supplementary heating arrangements.
| The heat pump performed well the entire winter.
|
| My energy bills are 1/2 of what I was paying with an
| electric furnace last year.
| rainsford wrote:
| > He does, but he omits a lot of important considerations
| that make heat pumps impractical for normal Americans.
|
| Some form of this comment always comes up in these heat pump
| threads, and I never understand the idea that heat pumps are
| some elite affectation that doesn't make sense for anyone
| else. Many millions of Americans live in parts of country
| where it gets warm enough in the summer to justify central
| air conditioning and chilly enough in the winter that you
| need heat but the heating source doesn't need to handle super
| low temps on a regular basis.
|
| A heat pump is literally one of the simplest ways to address
| the year round climate control needs for those people since
| it's a single system that handles both heating and cooling
| with only marginally more complexity than the air conditioner
| you'd want anyways. Throw in electric backup heat, which is
| probably the simplest backup and keeps the system all-
| electric, and you have a system able to handle a pretty broad
| range of temperatures all year. As heat pump technology gets
| better, the applicable temperature range gets colder and
| colder and makes heat pumps practical for a wider range of
| "normal Americans".
|
| This isn't just theoretical. Heat pumps account for 17% of
| heating systems in the US, which isn't huge, but over 40% in
| North Carolina, South Carolina, and Alabama and a significant
| percentage in many other states as well. Obviously there are
| cases where heat pumps are at least currently impractical
| given the construction, climate, etc, but dismissing them as
| some effete toy seems a bit silly.
|
| Edit: Interestingly, most states seem to have a significantly
| higher percentage of homes with electricity as their primary
| heating fuel than they do homes with heat pumps, suggesting a
| lot of homes with things like electric baseboard heating.
| While not all of those homes necessarily have central AC,
| using Georgia as an example, 85% of homes have central AC and
| 53% use electricity as their main heating fuel, while only
| 29% have heat pumps. That suggests quite a few homes _with_
| central AC that use electric baseboard or similar. Heat pumps
| for those homes seem like they 'd be very practical.
| snozolli wrote:
| _With a heat pump, you -need- an alternative source of heat -
| since some days when it 's particularly cold_
|
| Modern heat pumps redirect some heat to prevent the coils
| from freezing. What you wrote is common FUD pushed by the oil
| & gas companies.
|
| That said, you'd be a fool to live in an area with life-
| threateningly low temperatures and not have a backup heat
| source.
| guidoism wrote:
| The alternative heat point is interesting, you don't need to
| be able to heat your entire house with alternative heat for
| extended periods of time. If properly designed, 99% of the
| hours of the year should be warm enough for the heat pump to
| provide 100% to heat and the remaining hours can be made up
| with a small space heater or a fire or something else
| minimal.
| boringg wrote:
| What is going on? Is there a global push to get everyone to
| switch to heat pumps. It seems that there is heat pump content
| everywhere. Clearly there is a push.
|
| I understand that its for climate benefits but it feels very
| coordinated.
|
| edit: didn't realize the attention I would get. Let me add
| someone answered my question -- a good product market fit and
| people talking is probably where the push came from. That said
| HVAC installers / heat pump manufacturers and governments are all
| pushing this hard right now. I believe in the benefit for most
| people and the climate benefits are great. I am always concerned
| on when there is large consensus on a hard push - worth looking
| at who the winners are and what the trade offs are.
| atoav wrote:
| My father has solar and a heat pump. His cummulative heating
| and electrical cost is practically _zero_ over the year. On
| many days the solor panels produce more than he can use so he
| gets money for feeding it into the grid.
|
| If the roof of your house produces enough electricity for the
| people living it _and_ the heating (and cooling) of all rooms,
| it is a no brainer to switch to a form of heating that relies
| on electricity.
| helen___keller wrote:
| I've been independently interested in heat pumps because I need
| to replace my old end-of-life system and I've been interested
| if a modern cold-weather mini split system is a better
| investment. There's lots of conflicting info I've found on if
| heat pumps perform in freezing weather and at what kind of
| efficiency.
|
| I'm sure there's others in my position.
| kwhitefoot wrote:
| Heat pumps sold in Norway are claimed to work down to
| -30degC. See, for instance, the Samsung Nordic Extreme:
| https://www.elkjop.no/product/hjem-rengjoring-og-
| kjokkenutst...
|
| I don't know what the coefficient of performance is at that
| temperature though.
| rayiner wrote:
| I've got a mid-range Amana heat pump and even that has a COP
| of 2.1 (2 watts of heating per watt used) down to 0F.
|
| Heat pumps require different system design than a traditional
| setup, where the cooling load is usually the driving force.
| You might need a bigger heat pump to handle the heating load
| in very cold weather accounting for the efficiency loss.
| sbradford26 wrote:
| So largely I think the confusion stems from there being two
| major different "types" of heat pumps and they perform very
| differently.
|
| The first is your conventional type system, this is usually
| what AC units are in the US. They run at maybe 1 or 2 speeds.
| These type of heat pumps are common in the southern parts of
| the US but also will be found paired with a gas furnace in
| the northern US. Since they don't adjust their output
| dynamically they tend to start losing capacity/efficiency
| significantly around 25-30F.
|
| The second is an inverter driven heat pump. You usually find
| these in mini splits but they can also be found in a standard
| air handler form factor that would replace a furnace. The
| inverter allows the compressor to adjust based on demand and
| exterior temperature to maximize efficiency. This allow these
| units to operate efficiently down to -13F depending on the
| unit. Now there will still be some capacity loss at those
| temps so during the design of the system this has to be taken
| into account.
|
| For detailed information on the efficiency of heat pumps I
| would check out NEEPs website. It is a great resource, it
| will show you capacity and efficiency (COP) of tons of
| different units across their operating temperatures.
|
| https://ashp.neep.org/
| fullstop wrote:
| Where do you live geographically? I'm in eastern Pennsylvania
| and have lived with a heat pump for 20+ years.
| helen___keller wrote:
| Massachusetts
| fullstop wrote:
| A bit colder, on average, than where I live. You might
| want to look at ground-loop HPs or ccASHPs.
| mr_mitm wrote:
| You should expect this impression to become more intense. How
| else will you heat your home without emitting greenhouse
| gasses? Electric space heaters are vastly inferior for obvious
| reasons. Everything else is out because we eventually need to
| achieve (net) zero emissions. And since there are a lot of gas
| and oil heaters to be replaced, heat pumps will only increase
| in demand.
| achenatx wrote:
| my friend is building his house and is putting in 4 heat pumps
| (big house). The problem is we just lost power for 4 days and 2
| years ago we lost power for 5 days. He is discovering that
| electric heat uses massive amounts of electricity and there is
| no way to get a residential generator big enough to power them
| all. He might not even be able to power one (they can use in
| excess of 20kw).
|
| I would never get electrical water heater, stove, and heater
| for that reason.
| danans wrote:
| > my friend is building his house and is putting in 4 heat
| pumps (big house). The problem is we just lost power for 4
| days and 2 years ago we lost power for 5 days. He is
| discovering that electric heat uses massive amounts of
| electricity and there is no way to get a residential
| generator big enough to power them all. He might not even be
| able to power one (they can use in excess of 20kw).
|
| If he's building the house new, he should strongly consider
| investing in designing the building envelope in a way that
| 20kW heat pumps aren't required. It's very possible,
| especially with new builds.
|
| The models to follow are Passive House [1] and Pretty Good
| House [2]. There are many examples of large houses built to
| those standards in cold climates that use a heat pump that
| only draws 2kW, which could easily be powered by a generator
| or backup battery. This assumes that by "big house" we mean
| something still below ~3500sqft and not some kind of mansion.
|
| The basics are to get the building air leakage below 1ACH50
| (3-5x better than most codes, but not hard in a new build),
| and eliminate thermal bridging by using thick exterior
| insulation around the building perimeter.
|
| 1. https://passivehouse.com/
|
| 2. https://www.prettygoodhouse.org/
| boringg wrote:
| So this is one of my big concerns - I live in a cold weather
| country currently. We have power outages once every couple of
| years. If I don't have back up power my pipes freeze and then
| i'm out probably > $50k.
|
| I was thinking the solution for me is to put in a heat pump
| and then run a backup gas generator. But that solution feels
| like a significant amount of overbuild. I have 3 minisplits
| already but they aren't valuable in the winter -- where you
| install your AC units isn't where you would install your
| heating units .. I.e. the top of my house for AC, the bottom
| of the house for heat.
|
| Having multiple energy sources to defray risk is helpful.
| bluGill wrote:
| Heat pumps are great when things are mildly cold. While do
| work down to -20C or so, efficiency drops off, so you need
| bigger and bigger units. It often makes sense to have a
| smaller heat pump that will only work down to -5C (random
| temperature, a real analysis of your house is required to
| give a better answer), and then a gas furnace backup for
| those really cold days. Once you have the gas furnace
| backup you can run that off of a small generator on the few
| days you are without power.
| thekingshorses wrote:
| If there is a power outage, you can't run your natural gas
| heater either. It needs fan to run.
| triceratops wrote:
| But you can run a furnace fan off a diesel generator.
| p1mrx wrote:
| Why diesel? If you need natural gas to run the furnace,
| it might as well run the generator too.
| triceratops wrote:
| Maybe "fossil fuel powered generator" would've captured
| better what I meant.
| heisenbit wrote:
| Continuous improvements in technology, growth spurt in electric
| motors, demand gap for automobile motor part suppliers having
| to seek out related industries, cheap summer electricity via
| solar panel meet kick in the behind by fossil fuel energy
| prices.
| Maxburn wrote:
| YES. There is a massive electrification push right now because
| electric items can be fed from "sustainable" things like
| wind/dam/solar and don't emit CO or CO2 in operation.
|
| Heat pumps are also inexpensive on initial cost and less
| expensive than straight AC with gas heat.
|
| They are also low maintenance in comparison to straight AC with
| gas heat.
|
| Very popular units in southern US.
| bcrosby95 wrote:
| This hasn't been my experience. I can get an AC unit and gas
| furnace installed for something like 7k. But a heat pump unit
| that heats and cools is something like 13k installed. I
| obviously went with the former.
| fullstop wrote:
| How long do those units last, though, and what is their
| operating cost over their lifetimes? TCO obviously includes
| more than the initial cost of the equipment.
| Maxburn wrote:
| Gas heat probably should be tuned up for clean burning
| every year or two. A heat pump is generally good for
| years until something breaks. Both systems need filter
| changes and coil cleaning, which most homeowners can do
| themselves.
|
| Couple "fun" things about a heat pump; You will smell
| burning the first time the electric strips are used every
| year moving into the heating season, it's just dust
| burning off. Once you start moving into colder weather
| you might notice the system changing into defrost mode so
| it can melt ice off of the outside coils. There's a
| variety of sounds that accompany this and you might even
| see a bunch of steam coming off of the outside unit. It
| isn't smoke and it's normal. Every year there's a flood
| of 911 calls about this.
| PragmaticPulp wrote:
| The install price is only the start. The total cost of
| ownership over expected lifetime is the important number
| for many. That initial 7K installation cost is only a
| fraction of what you're going to pay in gas and electricity
| over the next decade.
| Maxburn wrote:
| Very true. Simply having gas available to use results in
| a base bill for service, even if your usage is zero.
|
| And yet what I see time and again is that initial
| purchase price is the only focus for construction costs,
| even rehab work. Those budgets are a separate bucket from
| utility bills so lower priced projects get approval even
| if utility bills will be higher.
| Maxburn wrote:
| That's fascinating and I believe you were subject to some
| weird market conditions there. Look at the complexity of
| gas burners vs a reversing valve and electric heat strips
| and I think you will see what I mean.
| Thlom wrote:
| I replaced my air-to-air heat pump for 3-4k last year.
| boucher wrote:
| It's worth mentioning that the Inflation Reduction Act is
| now providing for substantial subsidies for purchasing heat
| pumps (and other home electrification projects).
|
| Anyone doing the math today on a similar purchase should
| really check out how much they can get from the government:
| https://www.rewiringamerica.org/app/ira-calculator
| notdarkyet wrote:
| I see this as well and it looks to be multiple people buying in
| to the campaign, especially here on HN.
|
| Having lived in a new, high end apartment that had a heat pump
| for both heating and cooling for 3 years, I am very unimpressed
| with the tech. Running nonstop, couldn't heat/cool above/below
| a certain threshold. Electric bill very high. Clogged and broke
| a lot. If the general radiant heat and cooling from being in
| large building didn't exist, I couldn't see this working
| halfway decent in any place in the midwest. This might work for
| areas with less variable temperature ranges but for the midwest
| USA, not seeing it.
| PragmaticPulp wrote:
| Your singular experience is an outlier, not an example of
| totally normal circumstances.
|
| There is no conspiracy to push broken technology on to the
| masses. Heat pump technology has come a long way and modern
| heat pumps are very good at what they do.
|
| If someone installed a heat pump that doesn't work in the
| temperature range of your location, they really screwed up.
| Modern heat pumps can be selected to work down to very low
| temperatures, and they're installed with auxiliary heat when
| necessary. The design parameters aren't a mystery.
| flakeoil wrote:
| Also remember that air-to-air heat pumps are overall less
| efficient and powerful than air-to-water or geothermal-to-
| water type heat pumps.
|
| Firstly the later typically have a higher power rating.
|
| Secondly, if you can lead water around the house and heat via
| radiators or floor heating you get a much better efficiency.
| fullstop wrote:
| Your high end apartment must have had a low end heat pump
| installed.
|
| In the midwest a geothermal heat pump would work wonderfully.
|
| Also, they are designed to run constantly in order to
| maintain the set temperature -- it's not like a natural gas
| fired furnace where it quickly reaches the set point.
| prottog wrote:
| > Also, they are designed to run constantly in order to
| maintain the set temperature
|
| Not all heat pumps are variable-speed like you describe. My
| own home, built in 2000, has a single-speed heat pump that
| kicks on 100% or off, like a regular old AC unit.
| fullstop wrote:
| Right, what I'm trying to say is that it is normal for it
| to be on 100% of the time when it is cold out. If you are
| used to gas heat which can turn on for 15 minutes,
| overshoot the set point, and then be off for the next 45
| minutes, a heat pump will seem strange.
|
| Mine is a variable speed unit, but that's not the
| function that I'm talking about.
| slfnflctd wrote:
| What's the payback time on something like that for a modest
| home in a place which can get significantly under 20
| degrees (F) or over 95 degrees for weeks or longer? How
| effective is it at those extreme temperatures when it
| matters the most, and how does this affect maintenance
| costs?
|
| Additionally, there are multiple types of restrictions on
| where geothermal pumps can be installed, and navigating
| this can add to costs.
|
| I don't see it as a one size fits all solution, there are
| far too many people for whom the household/company math
| doesn't add up. However, I agree we should be doing fair
| comparison against other renewable-friendly options for all
| new construction. I'm sure heat pumps could win out in a
| great many situations, and we should use them where they
| do.
| timerol wrote:
| > over 95 degrees
|
| Note that a heat pump cooling a building is essentially
| the same as an air conditioner. So it's more a matter of
| how efficient the air conditioner you're replacing is.
| Cooling a house is much easier than heating, because the
| temperature differences are lower. In your example,
| cooling 95 F to 70 F is a 25 F difference, while heating
| 20 F to 70 F is a 50 F difference. The world record for
| heat is about 135 F, which is the same difference from 70
| F as 5 F, a completely normal winter temperature in much
| of the world.
| fullstop wrote:
| Obviously nobody can answer the long term cost
| differences between gas and heat pumps, since the cost of
| natural gas and electricity can change drastically over
| the lifetime of the unit.
|
| GP's comment was about the tech, though, and not the cost
| of said tech.
|
| It's absolutely not a perfect solution for all heating
| needs across the globe, the the technology is _far_
| better than GP is suggesting.
| slfnflctd wrote:
| In my view, natural gas is only competitive due to
| externalized costs and the slowdown/freeze of nuclear
| energy deployment. I recognize it's the only option for
| all kinds of situations (my dwelling heat included), but
| for anyone thinking forward it should be excluded in
| future development where possible.
|
| My main concern is the overall long term efficiency &
| affordability of renewable-friendly solutions, because
| competitiveness in those areas is what will lead to mass
| adoption. The point I was hewing toward is that I feel
| the heat pump advocates and providers need to make it
| more clear which situations are best suited for that
| solution and which are not, because it would benefit
| everyone.
| notyourwork wrote:
| The constant running also affords a more consistent
| temperature because air is continually moving. Decreases
| the temperature variance throughout the zone. I have a 3
| zone heat pump, 2 single room zones upstairs and a main
| floor with a air handler. We LOVE the setup so far.
| fullstop wrote:
| Yes, I've been happy with ours and it was a great
| improvement over the last heat pump that we had.
|
| Habits are hard to break, though, and there's not much
| value (if any) of lowering the set-point at night during
| the winter months. People still do it, though, and then
| the unit is working overtime in the morning to reach the
| desired set point.
|
| I'm glad that you're happy with your setup!
| LazyMans wrote:
| Just to clarify, it is more efficient to lower the set-
| point in the winter over night. The issue is when your
| thermostat is set to utilize aux heat if the delta is
| higher than your set point change in the morning. For
| example. If you change from 70 to 67 at night. In the
| morning when the set point goes back to 70, the
| thermostat is likely configured with an aux delta of 2 or
| 3 degrees. Meaning every morning the expensive resistive
| heater is running to raise your temp quickly.
|
| Personally, for my home and climate in the area, I
| disabled aux heat entirely, unless the temperature is
| below 0f outside, or if it hasn't reached the set point
| within 2 hours. Recently had some cold weather and these
| settings worked well for my home.
|
| I'm using an Ecobee, configurations will vary per
| thermostat. The big settings for me were using manual
| staging to configure the temperatures to engage aux,
| temps to lock it out, etc.
| LazyMans wrote:
| This is not the common experience, it's just an AC that runs
| in reverse. It sounds like a bad install/bad equipment.
| kodt wrote:
| 1. There was recently a statement released by a member of the
| Consumer Product Safety Commission saying they were considering
| regulating indoor pollution from natural gas stoves. This lead
| to a bunch of outrage and claims that Natural Gas was going to
| be banned at a Federal level.
| https://www.washingtonpost.com/climate-environment/2023/01/1...
|
| 2. Cites like NYC have implemented bans or limits on new gas
| installations, and it has been proposed at the state level as
| well. Other cities such as Chicago have had conversations
| regarding this issue, at least enough for it to get into the
| news and spark minor outrage.
|
| Because of these recent controversies there has been much talk
| about Heat Pumps and whether or not they are able to function
| efficiently or sufficiently in sub zero temperatures regularly
| seen in the upper Midwest or North East.
| Lutger wrote:
| Just the hivemind I guess, doesn't feel coordinated to me but
| rather obvious. In my country the waiting time for heat pumps
| is now over a year. People can't stop talking about energy, the
| war and their utility bills. Heat pumps are very on topic.
|
| Any reasons to change my mind?
| dsfyu404ed wrote:
| > What is going on? Is there a global push to get everyone to
| switch to heat pumps. It seems that there is heat pump content
| everywhere. Clearly there is a push.
|
| Based on the lack of political dick swinging I don't think this
| is a "push". They're legitimately good technology for certain
| use cases, I'm sure the manufacturers are pushing them. They
| are also The New Hotness(TM) and they are billed as
| environmentally friendly. Both those attributes are valuable by
| themselves to some people.
|
| I think this is more a case of a grassroots-originated circle
| jerk within certain demographic bubbles.
|
| I get a lot of "air fryer" vibe from the whole thing. And I say
| this as someone who owns and really likes his air fryer.
| rhussmann wrote:
| At least in NYC, new installations of gas and oil boilers for
| building and water heating will be regulated away in favor of
| electric-heating means (like heat pumps) by 2025:
| https://www.silive.com/news/2022/12/new-yorks-new-roadmap-to...
|
| This is, of course, the regulation as it stands today; things
| can always change. Additionally NYC alone likely doesn't
| account for the attention. But, other metros and municipalities
| could have similar legislation.
| Silverback_VII wrote:
| preparations for nuclear winter.
| kavalg wrote:
| I am a happy user of a DYI air source heat pump, that I've been
| using for 8+ years, mostly for heating in a residential
| building.
|
| First, it must be told that an off the shelf AC unit is
| technically speaking also a heat pump. There has been this
| distinction (and confusion) between AC units and (mostly)
| ground source heat pumps because, you know the latter actually
| have a water 'pump' to circulate fluid in the ground piping.
| Ground source heat pumps are far more expensive that AC units
| and are nearly impossible to retrofit in existing buildings.
| Hence, companies came up with a 'middle ground' solution,
| called air source heat pumps. In these devices the outdoor unit
| is much like an outdoor unit of a split type AC, but the indoor
| unit is basically a refrigerant/water heat exchanger with a
| water pump and some sensors around it. There is also a
| monoblock type of air source heat pump, where all components
| are in the outer block and you only connect the piping.
|
| IMHO, the reason air source heat pumps are becoming popular now
| is because their price went down considerably during the last 5
| years, whereas the price of fossil fuel heat sources has gone
| up. Back then when I had to choose between a gas boiler and a
| heat pump, the boiler was around EUR 2, off the shelf heat pump
| (24000 btu) was around EUR 7k and for the DIY option I paid a
| total of EUR 2.3k. The reason for this was that the market for
| air source heat pumps was underdeveloped and companies (e.g.
| Mitsubishi, Daikin, Fujitsu) were charging a lot more in this
| market segment (rich people with new houses). At some point in
| time, people started realizing the benefits of a heat pump over
| a normal AC (less units, no noise, nor air currents, better
| efficiency, can produce hot water, heating is decoupled from
| the source and more sources, such as solar can be seamlessly
| plugged in). Manufacturers albeit slowly responded to this
| demand.
|
| Now with solar power gaining more traction, they are becoming a
| very obvious choice.
| mhb wrote:
| That and gas stoves bad.
| mhb wrote:
| Google Trends: "heat pump", "gas stove":
|
| https://trends.google.com/trends/explore?date=2021-01-10%202.
| ..
| snuxoll wrote:
| The whole bit about gas stoves I have no doubt is a pretty
| typical astroturf campaign from the fossil fuel industry.
| They have shamelessly made up pro-gas nonprofits using fake
| personas, paid social media influencers to promote gas
| stovetops, and are likely behind the current "gubmit wants to
| take away your gas stove" trend that's drumming up online
| drama.
|
| One doesn't even need to look at climate impact to say gas
| stoves are bad, but focus the narrative on that one aspect
| and you can get climate deniers hyperventilating and
| defending their gas stovetop with statements like "you'll pry
| my gas stove from my dead hands". But really, economics are
| going to kill them all the same - induction stoves are
| dramatically more energy efficient, have the same benefits of
| fast thermal response, and don't pose a gigantic risk to life
| and limb every time you turn them on (or leave them off, for
| that matter).
| JTbane wrote:
| Gas stoves bad, yes. If you do a modicum of research you can
| see that they cause indoor air pollution (and most people
| don't have real hood vents to outside the building).
| rootusrootus wrote:
| The 'gas stoves bad' movement isn't a push, it's a pull.
| vintermann wrote:
| I think the underlying reason for it is that lots of
| engineering types got air quality sensors during corona,
| and noticed PM levels spiking from cooking. Or just people
| getting more IAC-conscious in general.
|
| This technology connections YouTuber I've seen pop up in
| lots of discussions on these topics.
| MrMan wrote:
| gas stoves are bad
| endemic wrote:
| I don't understand why this is contentious. You're burning
| gas inside your house.
| mikeyouse wrote:
| That's what is funny to me too -- they're basically
| phasing out all furnaces and hot water heaters that
| aren't direct vent (bringing in combustion air from
| outside) because it's so problematic to have gas-burning
| appliances in your home. Yet we just burn gas stoves --
| some of which are _massive_ without question...
|
| If you were to use all of the burners on this stove on
| their highest setting, it would consume more BTUs than a
| 6-ton Furnace! And it just vents into your indoor air:
| (https://www.homedepot.com/p/Cosmo-36-in-6-0-cu-ft-
| Commercial...)
| bluGill wrote:
| Most commercial stoves require a vented hood. Home depot
| may not tell you this, but the manual of the stove will.
| mikeyouse wrote:
| Apologies that link was broken -- but that was a
| "Commercial Style" stove for a home, not actually a
| commercial appliance. In any case vents are a really bad
| solution.. but they're inefficient at removing fumes, are
| usually undersized and too far from the cooking surface,
| and most people don't use them because they're
| obnoxiously noisy when running at the proper speed.
|
| A friend of mine just remodeled their kitchen -- they got
| all the permits and sign-offs, and their AHJ allowed a
| gas stove in the island with no venting at all. Inspector
| told them they should open a window if they were doing a
| lot of cooking. It's actual madness.
|
| https://i.imgur.com/ApCIyzS.png
| kortilla wrote:
| "Solution is bad when you don't do it!"
| mikeyouse wrote:
| Is it a "solution" when it's completely optional and
| rarely done correctly? This whole discussion reminds me
| of the 80s TV interviews that made the rounds this week
| about people complaining the government was infringing on
| their right to have a beer in the car on the way home
| from work (https://www.tiktok.com/@cali_nostalgia/video/7
| 19704298970805...).
|
| "It's my god given right to poison my family with CO and
| NOx!"
| elil17 wrote:
| Well of course it is being pushed, though I would not
| necessarily call it coordinated.
|
| Companies that sell heat pumps are advertising hard. It's an
| easy sell for them with rising gas prices.
|
| The US government is "pushing them" by offering tax credits for
| heat pump systems. This is part of a plan to reduce pollution,
| improve energy independence/energy security, and save citizens
| money on their heating bills. No secret there - politicians and
| public servants are excited about this and they are talking
| about it. They are also offering tax credits for other high
| efficiency heating systems, but not that many people are
| looking at those tax credits because buying a new high
| efficiency gas furnace doesn't make that much sense when you
| could buy a more efficient heat pump instead.
|
| Many individual people are also talking about them because they
| are a great way to help the environment and save money at the
| same time.
|
| And I think a lot of people just think they are cool technology
| as well.
| boringg wrote:
| I think this is probably the right answer. It keeps popping
| up everywhere.
|
| I'm always a skeptic on when something gets super hyped. In
| this case it's more use-case specific that makes me skeptical
| - majority of people its 100% fit.
| elil17 wrote:
| I also tend to be skeptical when I see something hyped, but
| I work in this space and I can say that this tech is really
| the best option for most residential applications.
|
| It's old tech, it's been around since the 1800s. The only
| thing that has changed is that heat pumps have gotten cheap
| and energy has gotten expensive.
|
| There are applications where heat pumps cannot replace
| boilers - in industrial processes where high temperatures
| are required or tremendous capacity is needed
| intermittently.
|
| However, unless your temperatures are routinely below about
| -20 F, a heat pump is the best choice (and even if
| temperatures occasionally drop below that, heat pumps are
| still an excellent choice because those extreme
| temperatures might only last for a handful of hours out of
| the year, during which insulation or a cheap electrical
| resistance heater can keep you warm).
| redeeman wrote:
| topic of discussion: is anyone else concerned that all the new
| things being clearly pushed hard, regardless of reasons(good or
| bad), has the common theme of centralizing. In a world where if
| your heatpump stops working, you die from cold, it would be an
| awfully sad thing if social credit scores dictated a very low
| kilowatthour limit. Much more sad than a world where you obtain
| firewood from some local vendor
| triceratops wrote:
| Did you know that installing a heat pump doesn't magically
| cause fireplaces in the house to stop working? Or that if
| you're concerned about being cut off from electricity because
| of your low "social credit score" the heat pump will run just
| fine off solar panels and batteries?
| pjc50 wrote:
| > Much more sad than a world where you obtain firewood from
| some local vendor
|
| A while ago I ran the numbers, and to meet UK electricity
| demand from wood would consume _every single tree_ in the
| country in three months.
|
| Limiting that to heating and giving up on industry would
| stretch that a bit, but the country is fundamentally
| dependent on imports to stay alive. We can't not be global.
| kevstev wrote:
| I am not sure the case you are making here- most people who
| would be switching to a heat pump for heat are almost
| certainly using oil, natural gas, or propane to heat their
| homes, all of which require a good deal of centralization.
|
| Those that have the ability to use firewood to heat their
| homes today can continue doing so if they need to- its not a
| requirement to close up your chimney permanently to use one.
|
| FWIW I am considering switching to a heat pump, but would
| still have natural gas fireplaces as a backup.
| PragmaticPulp wrote:
| > has the common theme of centralizing. In a world where if
| your heatpump stops working, you die from cold,
|
| Using machinery for heating isn't new. Virtually nobody in
| the modern world uses firewood from a local vendor to heat
| their homes.
|
| These conspiracy theorist angles are baffling. Heat pumps are
| just another variation of AC, which is already ubiquitous. If
| people don't use heat pumps, they won't use firewood. They'll
| use a regular furnace or electric heat.
| micromacrofoot wrote:
| They could also just shut off your gas, heat pumps introduce
| no newfound ability to be authoritarian that isn't already
| there.
| nicoburns wrote:
| > Is there a global push to get everyone to switch to heat
| pumps.
|
| I mean, yes. They're _much_ more energy efficient than the
| alternatives and will play a key part of removing our
| dependence on fossil fuels.
|
| > I understand that its for climate benefits but it feels very
| coordinated.
|
| That seems like a good thing?
| vintermann wrote:
| Yeah. If some people came together at Davos or whatever and
| decided "we need to promote heat pumps!", you can be sure
| they would mess it up. Consent can maybe be manufactured.
| Enthusiasm is organic, for good and bad.
| aliqot wrote:
| It's like you got to the endzone and fumbled with <5yds
| nicoburns wrote:
| Agreed that top-down programs aren't always very effective
| (although sometimes they can be), but would point out that
| "coordinated" doesn't imply top-down. It could just mean
| that lots of individual entities are working with each
| other to achieve a common goal.
| nashashmi wrote:
| They are not more energy efficient than burning gas.
|
| Edit: since i am getting downvoted to oblivion, let me fight
| back here. I genuinely wished heat pumps would be more
| efficient and in theory they can be. I would love to not
| generate heat and just use the outside heat energy and
| compress it down into a smaller location.
|
| But compressing and decompressing is not an energy efficient
| task. It takes a lot of work. Mechanical inefficiencies are a
| huge energy consumption. Gas is simply burning fuel. Yes, we
| should save gas for rainy days. But I hate to say that it is
| more efficient and cheap. There is no comparison.
| gabrielhidasy wrote:
| They literally are more efficient than burning gas, a good
| heat pump can do over 300% efficiency (KWs of heat in your
| house vs KWs of electricity used) while a furnace can only
| hope to get 100%. Even if the heat pump is fed from gas
| power plants (which burn gas with about 50-60% efficiency,
| more if the waste heat is reused), they are still using
| less gas for the same amount of heat than directly burning
| it.
| nashashmi wrote:
| 400% efficiency? Is that even possible? (Did AI write
| this?)
| Nihilartikel wrote:
| If I can spend 1 joule to transfer two joules of enthalpy
| from outside to inside, then that is 200% efficiency.
|
| Burning 1 joule of gas would give you 1 joule of heat in
| a perfect world. That is what a non pump does.
| vikingerik wrote:
| Where exactly does that first spent joule go,
| thermodynamically speaking? Is it also converted to heat
| within the electromechanicals of the heat pump?
| kenmacd wrote:
| To add to the other answer, if you calculate the absolute
| limit on performance for heating and cooling using the
| Carnot cycle, the 'heating' case is always going to be
| '1' higher than the cooling case, because you also get to
| use the 'work' heat.
| SigmundA wrote:
| Yes so not only are you capturing heat from the
| environment you are turning electricity into heat in the
| compressor, both are delivered as heat to the interior.
| This is an advantage compared to cooling where you must
| reject both the interior heat and the heat of
| compression.
| aaronax wrote:
| More technically it would be a coefficient of performance
| of 4, which in some frames of reference is like 400%
| efficiency.
| kortilla wrote:
| Yes, because a heat pump is taking the heat from the
| outside environment and moving it into your house. You're
| only paying the "transportation cost" and not the actual
| cost to generate heat. The heat was generated by the sun.
| SigmundA wrote:
| https://en.wikipedia.org/wiki/Coefficient_of_performance
| nicoburns wrote:
| If you measure the efficiency of heat output relative to
| the electrical input power, then yes. The trick is that
| there's actually another input: latent heat in the
| environment. But given that this is abundant and freely
| available we don't usually bother to include that in our
| calculations.
| thehappypm wrote:
| Yes, you might want to do some research on it.
|
| The core idea is that you aren't using 1 unit of
| electrical energy to create 1 new unit of heat energy.
| You are using 1 unit of electrical energy to capture
| several units of pre-existing heat energy from the
| environment and pump it indoors.
| sbradford26 wrote:
| So the term efficiency with heat pumps typically refers
| to COP Coefficient of Performance. It a measure of how
| many watts of heat you are able to pump per given watt of
| electricity used. So 400% would be a COP of 4.0 which is
| definitely possible with air source heat pumps in milder
| weather and ground source heat pumps in pretty much any
| weather.
| titannet wrote:
| If that where there would be no discussion about the
| switch to heat pumps. But it isn't. In old houses (bad
| insulation, old radiators) and edge cases ("winter") heat
| pump are not just inefficient they may not be able to
| heat the house at all (unless extremely oversized).
|
| This is a huge problem in Europe where a house is
| expected to last a 100 years, in many areas much more.
| nicoburns wrote:
| It's true that good insulation and sufficiently sized
| radiators are important. But it's not like those things
| can't be upgraded in existing houses. In fact, if we're
| talking about energy efficiency then insulating houses
| should likely be the first action taken.
| guidoism wrote:
| Slightly unrelated, I have a friend who moved to the US
| from Mexico and was asking me about potentially buying a
| house. He started looking on Zillow with me and his
| reaction to houses build in the 1950s OMG how can it be
| that houses are that old and my reaction was wow that's
| pretty much a brand new house. He was blown away that a
| huge percentage of houses on the market are from the
| early 1900s and even late 1800s where we live.
| amiga386 wrote:
| Sorry for nit-picking, but gas power plants burn 50-60%
| efficiency _when_ waste heat is reused, compared to
| 30-40% efficiency with a single cycle.
|
| https://en.wikipedia.org/wiki/Combined_cycle_power_plant
|
| > (CCGT) plant[s] achieve a best-of-class [...] thermal
| efficiency of around 64% in base-load operation. In
| contrast, a single cycle steam power plant is limited to
| efficiencies from 35 to 42%
| steve76 wrote:
| [dead]
| SigmundA wrote:
| They can be, natural gas is about 1000 BTU per cubic foot.
|
| An expensive high efficiency gas furnace might be 95%
| efficient (most normal furnaces are in the 80's)
|
| 1000 x 0.95 = 950 BTU/cuft
|
| A high efficiency natural gas power plant is 60% efficient
| and a modern high efficiency low temp heat pump can have a
| COP up to around 2.7 at 17F
|
| 1000 x 0.6 x 2.7 = 1620 BTU/cuft
|
| A 40% power pant is still more efficient than a 95% furnace
| with a 2.7 COP heat pump.
|
| There is obviously more to this, there are some grid losses
| to account for but has to be compared to piping losses,
| there is also cost factors and also how much renewable is
| mixed into your grid supply, but generally once that heat
| pump is above around 2.5 COP it starts to make sense, this
| is a no brainer in milder climates which is why I have a
| heat pump and no gas furnace here in FL even though I have
| gas to the house for other uses.
| snuxoll wrote:
| > this is a no brainer in milder climates which is why I
| have a heat pump and no gas furnace here in FL even
| though I have gas to the house for other uses.
|
| They're a no-brainer in every climate. Newer heat pumps
| can handle fairly cold temperatures (-13degF) pretty
| easily, there may be a loss in efficiency but in the
| majority of the world it doesn't _stay_ that cold. A few
| days of lower than normal efficiency, and at worst
| plugging in a few space heaters if it gets extremely cold
| for a day or two, does not change the overall math of
| heat pumps being a better solution.
|
| Hell, that's just me talking about _air source_ heat
| pumps. No reason for new construction to not use ground
| source and get better efficiency and not worry about
| ambient outdoor temperatures.
| sbradford26 wrote:
| So heat pumps do lose efficiency at lower temperature
| such as -13F but the much bigger issues is loss of
| capacity. If you look at the curve of available heating
| capacity of a heat pump versus the heating needs for your
| house that tend to be a bit of a mirror image. When it is
| warmer out your house needs less heat but heat pumps have
| the highest capacity they will have. As temps drop the
| house will require more heat while the capacity of the
| heat pump is dropping.
|
| That isn't to say they cannot work I personally have a
| heat pump in my house and it worked fine through the -15F
| weather we got. But it requires careful design work
| initially. Also you run into simply size constraints
| where residential heat pumps tend to max out at 5 tons
| (60k BTUs) typically when furnaces can easily get up into
| the 100k+ BTUs. Which might require multiple heat pumps
| and separating existing duct work. But definitely new
| construction should start designing around these
| constraints now.
| snuxoll wrote:
| > Which might require multiple heat pumps and separating
| existing duct work. But definitely new construction
| should start designing around these constraints now.
|
| Ductless mini-splits remain an option as well. I'd
| actually like to see somebody make some ground-source
| exchanger that ductless heads could connect to, because
| they're much cheaper to install than a multi-zone ducted
| system.
| sbradford26 wrote:
| They make systems like that but they tend to be more
| commercial systems. You could get a ground to water heat
| pump then run chilled/heated water to the mini split
| heads depending on what they are calling for but even
| that is pushing into commercial territory. And sadly with
| commercial HVAC comes significantly higher prices.
| elil17 wrote:
| In cold climates, systems have backup electric furnaces.
| nashashmi wrote:
| Ok! I am genuinely interested in how heat pumps are more
| efficient. My online search led me to calling heat pumps
| more efficient when compared to electric heaters. And
| better in other ways compared to gas burners. But lord's
| sake, they were all upselling marketing sites for heat
| pumps.
|
| I am looking for genuine research, and not from paid
| mouth pieces.
|
| Majority of the comments here seem like agents of heat
| pump industry. And HN rules forbid me from calling them
| that.
| kevstev wrote:
| Did you watch the video linked on the highest rated post
| on this thread? The one from technology connections? It
| explains it all very well.
|
| I am happy you have an open mind, but the fact that you
| are trying to tear the technology down when you
| apparently have no idea how it works or what it even is-
| hopefully you realize that it is also used for air
| conditioning, and is essentially just an air conditioner
| running in reverse... I hope this is a learning
| experience for you.
|
| At the very least it gives me hope that those trying to
| tear down this technology are just ignorant, I had real
| suspicions that they were agents of the fossil fuel
| industry, or this was something Fox News and the like
| decided to target and is now being parroted.
| SigmundA wrote:
| Just do the math, all you need to know is furnace
| efficiency and COP of the heat pump along with the
| efficiency of your local power plant. I did that in my
| post, its not super complicated.
|
| Gas is burned creating a certain amount of heat, in a
| furnace some is lost to exhaust the rest goes into your
| house. That is the furnace efficiency.
|
| When gas is burned at a power plant the same number of
| BTU is released, but it is used instead in a heat engine
| to create mechanical power which is then turned into
| electrical power, the rest is lost to exhaust, this is
| the power plant efficiency.
|
| Heat pumps are over 100% efficient because they capture
| heat from the environment around your house which is
| warmed by the sun. So even though more energy is lost in
| creating electricity than burning directly in your house,
| this is more than made up for by using the ambient heat
| around your house, it is essentially solar assisted (in
| the case of air source).
| snuxoll wrote:
| Physics. When combusting fuel you cannot get more heat
| energy out of them than the chemical bonds you are
| breaking contains, a gas furnace can never be more than
| 100% efficient, the best commercially available ones are
| 95%, and a majority that are actually installed are
| closer to 80-90%.
|
| Heat pumps do not create heat, the refrigeration cycle
| _moves_ heat from point A to point B. For every KWh of
| electricity used by your refrigerator, air conditioner,
| or heat pump, 3-4 KWh of _heat energy_ can be moved where
| you want it to go.
|
| Even if you have a (comparatively) inefficient combined
| cycle natural gas power plant that is 50-60% efficient,
| you're still getting 150-200% efficiency for heating with
| a heat pump compared to 80-95% for a natural gas furnace.
|
| I live in Boise so we have pretty cheap utilities
| compared to the national average, but here's some math:
|
| 1 therm (~30KWh of energy) is ~$0.72 from Intermountain
| Gas, the furnace in my rental is 90% efficient, so I
| actually get 27KWh of heat from every therm I burn.
|
| Idaho power has a tiered tariff for residential
| customers, with a peak charge of ~$0.098 per KWh during
| the winter for usage over 2,000 KWh in a month.
|
| Every therm my gas furnace burns costs me as much as
| ~7.5KWh from the electric utility, but those 7.5KWh can
| provide me with 30KWh of heat with a quality heat pump,
| which would require a 100% efficient natural gas furnace
| to reach. Add in that gas furnaces have a much higher TCO
| because of maintenance and repair compared to a heat
| pump, and they're not just energy inefficient in
| comparison but even just plain more expensive to operate
| even with incredibly cheap fossil fuels.
| nashashmi wrote:
| I am in NY. And I think for Florida, a heat pump makes
| because of a hybrid AC model. Even if electricity is more
| expensive, the equipment and energy cost of a separate
| unit is not worth spending.
|
| In extreme climates, gas burning is cheaper. And quite
| clean. There are some objections because of delivery
| leaks, but that is a separate concern.
| boucher wrote:
| As pointed out by several other comments, you're very off
| base about heat pump efficiency and about natural gas
| being "clean."
|
| Switching everyone to heat pumps would lower emissions
| from heating and cooling in the US by 160m tonnes a year
| [1], which is something like 30-40%.
|
| It's true that upfront costs of heat pumps can be higher,
| but thanks to the IRA there are huge subsidies available
| (and further subsidies in many states) which make up most
| or even all of that difference. The lifetime costs of
| heat pumps with these subsidies should be substantially
| lower than high efficiency natural gas furnaces.
|
| [1] https://www.rewiringamerica.org/circuit-breakers-
| heat-pumps
|
| (Those subsidies, by the way, are one of the reasons
| "everybody is talking about heat pumps")
| steve76 wrote:
| [dead]
| SigmundA wrote:
| Just to counter your edit:
|
| >But compressing and decompressing is not an energy
| efficient task. It takes a lot of work. Mechanical
| inefficiencies are a huge energy consumption. Gas is simply
| burning fuel. Yes, we should save gas for rainy days. But I
| hate to say that it is more efficient and cheap. There is
| no comparison.
|
| You are very mistaken, the energy required to compress
| refrigerant is less than the energy captured and delivered
| if COP > 1, which is the point of a heat pump. At COP 1 it
| is basically heat of compression and equal to a resistive
| heater at COP greater than 2 the heat pump captured more
| heat from the environment than used to compress the
| refrigerant.
|
| I am not sure if you are arguing in good faith, if so here
| are some of the simplest resources I can find to explain
| how a heat pump can exceed a furnace in efficiency even
| when taking power plant and transmission losses into
| account, with easy to understand graphics:
|
| https://greenbusinesswatch.co.uk/cop-vs-spf
|
| https://energyeducation.ca/encyclopedia/Coefficient_of_perf
| o...
|
| http://hyperphysics.phy-
| astr.gsu.edu/hbase/thermo/heatpump.h...
|
| This should really be taught and drilled in lower
| education, the difference between heat and temperature and
| relationship to power, how heat engines work, etc. This
| stuff basically makes modern society possible and we will
| never progress in decoupling our power sources from use of
| the power which is what electrification allows which allows
| us to transition away from throwing carbon up in the air
| for energy.
| pjerem wrote:
| Yes they are. You get more heating from an heat pump
| running from electricity coming from gas plants than what
| you get by just burning the gas. Including losses on the
| grid.
| nashashmi wrote:
| I cannot imagine this in anyway. Heat pumps work like ACs
| do. They do compress a medium till it heats up, and then
| spread that heat around. And then they decompress until
| it cools down and dump that cold until outside heat
| brings up the temperature again.
|
| Those compressions and decompressions take up immense
| amounts of energy. They are less efficient than simply
| burning gas. On the flip side, could we not create
| electricity generation and heating from Natural gas?
| elil17 wrote:
| I think you are misunderstand where most of that energy
| comes from. Say I have some refrigerant in liquid form at
| a low pressure. That refrigerant will have a boiling
| point of say, -20 degrees F. I use the ambient air, which
| is say 0 degrees F, to boil the refrigerant into a gas.
| The internal energy of the refrigerant goes up
| significantly, but it's temperature does not change.
| Then, I compress the gas so that it goes up in
| temperature. This change in temperature does _not_
| correspond to a large change in the internal energy of
| the gas. The same energy is pushed closer together,
| resulting in a higher temperature[1]. Then, I condense
| the gas at it 's new boiling point, say 100 F, into a
| liquid. Then you decompress the resulting liquid and the
| cycle repeats.
|
| Most of the energy is coming from the ambient air, only a
| small amount of electricity is used to change _what
| temperature_ that energy is available at.
|
| [1] A very simple mental model you can use to understand
| the difference between temperature and energy for a gas
| is that temperature is the number of times the gas
| molecules bump into each other in a second, while energy
| is how fast the gas molecules are moving. So if you have
| a very low pressure gas, even all of those molecules have
| a ton of energy in the form of motion, the temperature of
| the gas will be quite low because the gas molecules won't
| interact often. But compress that gas down to a small
| volume, and the molecules will bump into each other all
| the time even though they don't have much more energy.
| baxuz wrote:
| That's the whole point. For most modern systems you get
| >4x of the energy in heat exchange compared to the energy
| you put in. You don't produce heat, you exchange it.
|
| https://www.wolf.eu/en-de/advisor/cop-heat-pumps
| nicoburns wrote:
| Well of course when talking about efficiency you have to
| specify what you are being efficient with respect to:
| what's most energy efficient might be different to what's
| most cost efficient which might be different to what's most
| carbon efficient.
|
| Cost is going to vary greatly on the electricity and gas
| prices in your area, so it's hard to give a definitive
| answer there.
|
| With regards to energy efficiency, my understanding is that
| heat pumps can be up to 400% (300% typical), which is
| naively much better than gas which is at most 90% efficient
| (70-80% typical). This doesn't take into account the extra
| innefficiency of generating the electricity in the first
| place, but a quick google tells me coal plants are
| typically 33% efficient, with combined cycle gas plants
| being typically being 50% efficient. Even at those levels,
| heat pumps still look to be coming out ahead to me. And
| that's not even taking into the possibility of green energy
| generation through renewables or nuclear.
| zeroonetwothree wrote:
| There is also up to 10% loss from
| transmission/distribution. So that makes the two closer
| though heat pumps still win.
| elil17 wrote:
| Yes, heat pumps do win. They win even more when you
| consider that the energy mix is not 100% fossil fuels.
| Globally something like 15% of energy comes from
| renewables or nuclear, plus 20-ish % from natural gas
| which is, as you said, 50-ish % efficient in turbine
| power plants.
| Nihilartikel wrote:
| The new order world government will have to pry my wood
| burning lightbulbs from my cold dead guns!
| kzrdude wrote:
| Who do you imagine is pushing, and why?
|
| Don't you want to resist to turn to explanations like this,
| that require some invisible force to pull the strings? I think
| there are more realistic ways to imagine this happening.
|
| If for example a pop star is getting a lot of attention, in
| multiple countries, what is the mechanism behind that? And is
| it orchestrated?
| suoduandao2 wrote:
| Explanations like what? Op didn't put forward much in the way
| of hypotheses. If you have a good explanation of the
| mechanism by which attention accumulates around topics that
| doesn't require orchestration it would be interesting to
| hear, it seems like a poorly understood phenomenon.
| kzrdude wrote:
| The way I read it, Op was suggesting a flirt with
| conspiratorial thinking ("someone is doing this") and I
| wanted to turn to something more rational.
|
| I don't really know how trends and fashions form and
| haven't thought so much about it. Some aspect of it might
| look like research into the ising model and phase
| transitions - small changes in "temperature" everywhere in
| the mass of people might look like a phase transition in
| the overall mood.
| rcme wrote:
| It's called: product market fit. When people like your
| products, they talk about them.
|
| I have heat pumps through a mini split system. I like them
| so much I'm redoing my entire HVAC to add ducts with heat
| pump powered heating and AC. They're kind of a miracle:
| they produce great heat (way better than a gas-powered
| furnace), they're ultra-efficient, and they're whisper
| quiet.
| scythe wrote:
| I'm just annoyed that I was talking about heat pumps for the
| last five years or so and nobody is giving me any credit for
| running an international conspiracy.
|
| But seriously, it's just the next fish to fry after electric
| vehicles became a solved problem. Heating buildings is
| somewhere around 10-25% of total emissions and probably the
| largest remaining single factor not directly addressed by
| switching the electric grid to renewables, so many people
| concerned about climate change have converged on it.
| jjtheblunt wrote:
| Wait till we have Heat Pumps built with Rust!
|
| But seriously i think it's just that awareness hit a critical
| threshold so the hysteresis kicks in and articles proliferate.
| In both cases.
| PaulDavisThe1st wrote:
| There's really no question that Rust will undoubtedly take
| over most heat pumps, sooner or later.
| jjtheblunt wrote:
| :)
| nashashmi wrote:
| Heat pumps are the opposite of AC. AC industry is behind this
| for sure. It is like a paid PR campaign. It is not more
| economical then gas. So now gas is going to be punished for
| factors X,Y,Z.
|
| It is coordinated. I wish there is more investigative research
| into who and why they are doing this.
| jamiek88 wrote:
| In this thread you've gone form 'compressors don't work like
| that' to 'this is all a conspiracy by big A/C'.
|
| You are not engaging with any of the helpful, generous
| replies, in fact going as far as to say that you wish you
| could call it 'coordinated'.
|
| Why are you even here if you think we are all lying shill for
| big air compressor?
| WatchdogReset wrote:
| For the record, I am only trying to make my elearning website
| more known. There is plenty of other HVAC subject that I
| would like to share. It's just that Heat Pump where for me an
| interesting topics to get into the subject but you can have a
| look at other free courses.
| mikeyouse wrote:
| Ah yes, "big AC" is bullying the Oil and Gas industry with
| their subversive marketing. If only Exxon, BP, and Shell had
| some political clout they could expose this plot.
| billjings wrote:
| Here's a couple of reasons:
|
| 1. The American market has a lot of incorrect perceptions of
| heat pumps. Debunking these makes for great viral content! 2.
| The IRA introduced big incentives for various electrification
| expenses.
|
| The incentives are the big thing, but the public
| interest/controversy part is why some enhancements like heat
| pumps and kitchen electrification ("don't take away my gas
| stove!") are going more viral than, say, electric vehicles
| (technology connections guy has some good EV content, but it's
| not doing quite the same numbers)
| sophacles wrote:
| What is IRA in this context? I don't think heat pumps have
| anything to do with retirement nor the political status of
| Norther Ireland.
| aaronbrethorst wrote:
| The inflation reduction act of 2022.
| https://www.hvac.com/resources/inflation-reduction-act-
| heat-...
| billjings wrote:
| Yep, the Inflation Reduction Act is what I meant. It came
| into effect this year.
| tekla wrote:
| Its a fairly easy to parse typo of IRS.
| sophacles wrote:
| Oh that makes some sense, I guess I wasn't thinking about
| them since they aren't the ones who change tax law.
| practice9 wrote:
| The reason is that suddenly everybody understood that Russia is
| an unreliable partner for their countries energy needs (at
| least in Europe).
|
| For consumers it's also became clear that being slightly more
| independent from centralized heating and/or energy
| infrastructure is a good thing
| manojlds wrote:
| Suddenly, as in Crimea didn't happen?
| roywiggins wrote:
| Suddenly _understood_
| ZeroGravitas wrote:
| There was a push towards renewables and heat pumps after
| Crimea too (and before, for general climate change reasons)
|
| There was also push to do the opppsite to neutralise that
| threat to fossil profits e.g. Bjorn Lomberg the skeptic
| saying that we didnt have any tech that could replace gas,
| so the only response to Crimea was to frack or invent
| totally new tech, not rolling out renewables and heat pumps
| faster.
|
| "Fracking Could Free Europe from Putin"
|
| https://www.forbes.com/sites/bjornlomborg/2014/06/23/fracki
| n...
|
| > Still, many EU politicians talk mostly about expanding
| renewable energies as a way of making Europe independent of
| Russian energy. Connie Hedegaard, the European Commissioner
| for Climate Action, said the Ukraine crisis should be a
| "wake-up call" for European countries to make the switch
| from Russian gas to clean, renewable sources of energy.
|
| > But this simply ignores reality. According to the
| International Energy Agency (IEA), Europe gets just 1.3
| percent of its energy from renewables like solar and wind,
| whereas it gets about 75 percent from fossil fuels and most
| of the remainder from nuclear. Even an extremely optimistic
| scenario from the IEA suggests that by 2035, Europe will
| only be able to generate 8 percent of its energy from these
| renewables. Focusing on them is simply populism without
| realism.
|
| At that point, climate skepticism was strong enough
| politically to prevail. They tried to use this latest
| annexation to promote fracking etc. too but it seems to
| have largely failed.
| WatchdogReset wrote:
| My two cents, I just tried to show this free course on my site,
| because heat pumps are an interesting topic. There is also
| others courses like this : https://hvac-
| learning.com/courses/air-handling-units-technol...
|
| Heat pump as every heating or cooling devices, have pro and
| cons. This is where HVAC knowledge is nice to have, in order to
| have the best solutions. For example, the maintenance /
| obsolescence are an under estimated point when it comes to
| environment and savings
| guidoism wrote:
| It would be _great_ if this was coordinated. Ideas that are
| good for people usually don 't get a very intelligent effort
| promoting them compared to really bad ideas that make a few
| people really rich.
| danans wrote:
| > worth looking at who the winners are and what the trade offs
| are.
|
| The winners are consumers, the effort to reduce GHG and
| particulate emissions, and the drive toward energy independence
| (whether at the national, local, or hyper-local level).
|
| The losers are fossil fuel extraction industries, because due
| to the high COP of heat pumps, far more heat is delivered per
| unit of energy consumed, even if that energy ultimately comes
| from burning natural gas at a power station. Also, the source
| of the energy itself gets disintermediated, since electricity
| can come from multiple sources, including renewables.
|
| The tradeoffs are (for now): Higher upfront installation cost
| (tempered by the IRA, and potentially lower operating costs),
| availability of the equipment (supply chain stuff), and long
| delays in installation due to lack of qualified installers (and
| resulting high costs).
| bilsbie wrote:
| Easier to turn off people's electric than gas when they don't
| follow the social rules.
| dahfizz wrote:
| A more plausible explanation is that the we HN-ers are a bunch
| of nerds and heatpumps are excellent nerd-bait
| peterhunt wrote:
| It is coordinated. In many states there are huge incentives [1]
| to disconnect your existing home from (and not connect new
| construction to) the natural gas infrastructure.
|
| This is great for the climate but air source heat pump
| technology simply doesn't work well in cold climates. Most heat
| pumps in the United States have 100% efficiency down to about
| 20 degrees F. Below that they "lose efficiency."
|
| What most people don't realize is that "lose efficiency" =
| blows cool or cold air. So if you live somewhere that routinely
| gets that low you are likely either going to be really cold, or
| have to engage aux heat (often natgas or oil-based heating or
| electric resistance heating).
|
| Additionally, even when operating at 100% efficiency they don't
| blow air as hot as traditional heating sources. So if you have
| a poorly insulated room, large space, or even just an unusually
| cold day, it will often have a hard time keeping up.
|
| I have found that I only use my air source heat pump a little
| bit during the fall in New England, and I have to run aux heat
| throughout basically all of winter. Talking to my friends in
| the region who have heat pumps, they all have similar
| experiences.
|
| I think we are all very eager to get off of fossil fuels but
| the technology just isn't there yet, and I am concerned that
| most people installing heat pumps today don't know the risks
| associated with them in extreme weather events. If your heat
| pump can't keep up and you didn't install aux heating you can't
| live in your house, your pipes will freeze, and you will
| generally have a bad time. If you did install and use aux
| heating, you may be surprised at how expensive and inefficient
| resistive electric heating is as it may need to run all the
| time.
|
| [1] Massachusetts will pay you $10k to install air source heat
| pumps and disconnect from natural gas
| https://www.masssave.com/en/residential/rebates-and-incentiv...
| snozolli wrote:
| _Most heat pumps in the United States have 100% efficiency
| down to about 20 degrees F. Below that they "lose
| efficiency."_
|
| Most things that are already installed are worse than the
| latest technology that's available.
|
| That's not an argument against the latest technology.
| peterhunt wrote:
| I'm talking about the ones sold in the United States in the
| last few years. Mine is a Carrier manufactured in 2022
| nicpottier wrote:
| This is FUD. I live in climate zone 5 in a 100 year old house
| that has high heating demands and our air source heat pump
| has been awesome, even when it dipped into the negatives
| briefly this year. Our heat pump is over 100% efficient down
| to 0F.
| peterhunt wrote:
| What type of heat pump do you have out of curiosity?
| mschuster91 wrote:
| > Clearly there is a push.
|
| Yeah, tl;dr: fuel price scares and the French nuclear power
| plant disaster, as well as government regulations.
|
| To expand: most homes traditionally are heated by either
| burning something fossil (oil, gas, coal), somewhat half-ish
| renewable (wood pellets, straight chopped wood), by straight
| electricity (resistive heating) or by heat pumps (air-to-air,
| ground-to-air, deep-well-to-air aka geothermal). Some homes
| particularly in urban areas or in close proximity to a large
| power plant can also be heated by district heating using one of
| the aforementioned heat sources.
|
| And all of these classes of heaters have their issues:
|
| - Electricity is the easiest of the bunch from a technical
| point of view, but you're out of luck when the grid fails for
| whatever reason, you're tied to grid price hikes in some
| contract models (as people learned the hard way in Texas' last
| winter spike), there will be fuel burned as part of the
| generation and frankly resistive heating is wasteful.
|
| - Wood pellet has the problem that the amount of waste
| (=sawdust) is finite, which means you're chopping down wood
| that could be used for construction and burning it instead.
| That is a waste of money and valuable resources when wood is
| scarce, fine particulate matter causes smell and health issues,
| and a lot of wood is unethically sourced.
|
| - Solid-wood or coal heaters are difficult to properly fire up
| - most people fire it wrong (not enough oxygen / too much fuel
| load), resulting in higher consumption of wood, higher
| emissions and a danger of soot buildup which is a fire risk.
| Additionally, many home fires are started by people disposing
| not-completely-cooled ash or placing flammable objects too
| close to the oven or exhaust, and still a lot of people die
| because of carbon monoxide emissions caused by improper
| handling.
|
| - Oil stinks to hell and beyond, the boilers need an insane
| amount of maintenance so they don't clog up, you need to ship
| tanker trucks to homes, there are risks of spillage and
| contamination, and the same emissions issues of wood apply
| (plus, oil generates more CO2 than gas per kWh of heat). Also,
| it's not renewable at all.
|
| - Gas is relatively easy to ship around when there is a gas
| distribution network in place, it burns relatively clean, but
| carries an explosion risk and is fossil in origin (at least for
| the next decades that it will take to build up power-to-gas
| infrastructure).
|
| In contrast, heat pumps are pretty awesome:
|
| - all they need is a bit of electricity - a good heat pump can
| achieve up to 4x ratio, meaning it generates 4 kWh of available
| heat in the home by using 1 kWh of electricity. That also makes
| off-grid or local generator fallback solutions more feasible -
| a 20 kW heat-pump boiler needs a 5 kW generator which can be
| had for a couple hundred dollars instead of a massive generator
| unit.
|
| - their heat sources (or rather, cold sinks) are renewable -
| air, local ground loops or deep wells are virtually infinite.
| That means, as long as your electricity supply is renewable,
| your heat generation _also_ is renewable.
|
| - Most heat pumps run at 40-ish degrees. That in turn prohibits
| the use of old-school convection radiators, so most
| installations with heat pumps tend to use floor heating which
| needs less energy to achieve a temperature comfortable for
| humans (our feet are the most sensitive part, but as heat from
| a convection radiator rises to the top of the room, it needs a
| lot of energy for a comfortably warm floor).
|
| - they are, particularly when compared to oil heating,
| extremely small and don't cause emissions
|
| - they don't need much maintenance effort to keep running, and
| no need for chimney sweepers either
|
| - they don't pose an imminent risk of carbon monoxide poisoning
| or outright fire
|
| Basically, the only issue heat pumps have is you need specially
| trained people to install them and they are short in supply at
| the moment since everyone and their dog got shocked to heaven
| in the last year of that goddamn war and heat pumps are the
| objectively best way to heat a home.
| micromacrofoot wrote:
| It's a great way to lessen the demand on fossil fuels and the
| power grid.
|
| Manufacturers are obviously pushing, but many utility companies
| and municipalities are too. Basically the electric car or solar
| panels of HVAC. It's one of those things where there are a lot
| of incentives for everyone involved all the way down the line.
| [deleted]
| hexmiles wrote:
| I don't know if it applies everywhere, but two factor come to
| mind: the (somewhat recent) change in energy and gas price did
| make heat pump a lot more competitive with more traditional
| heating solutions, and recently there are a lot of economic
| incentives (at least, here in Europe) to renovate house for
| energy efficiency, which make solar panel and heat pump very
| attractive.
| masklinn wrote:
| > and recently there are a lot of economic incentives (at
| least, here in Europe) to renovate house for energy
| efficiency, which make solar panel and heat pump very
| attractive.
|
| Economic but also legal and geopolitical: fuel oil furnaces
| are getting restricted or banned, and the combination of
| climate change, air quality standards, and russian
| instability makes gas look at lot worse than it did 10 or 20
| years back.
| burkaman wrote:
| Yes, there is currently a coordinated push by the entire world
| to prevent excessive climate change.
| wongarsu wrote:
| For a long time the main problem of heat pumps was that while
| they are more efficient, a kilowatthour of gas or oil is much
| cheaper than a kilowatthour of electricity. But in the last two
| years natural gas prizes have gone crazy, removing that price
| disadvantage.
|
| Of course heat pumps emitting no particulates and being able to
| run on renewables are also good reasons, especially as the
| health impact of living in cities with high PM2.5 values
| becomes clearer. But I don't think those are the primary
| drivers.
| PragmaticPulp wrote:
| Heat pump technology has also improved significantly. You can
| now buy heat pumps that remain efficient down to very low
| temperatures, which makes them appropriate for a larger range
| of climates now.
|
| Many models are in very high demand. Some of the units I
| looked at recently were back ordered so far that I was told
| to pick something else if I expected to have it within the
| year.
|
| The demand is very high because the technology is good. It's
| not a campaign or conspiracy.
| bmicraft wrote:
| Yeah it almost makes the opposite of sense. If
| manufacturers are already backordered a year in advance why
| would they still throw money at marketing
| bluGill wrote:
| The war in Ukraine has resulted in a real push to get off
| of oil/gas based heating, on top of global warming
| concerns that have already been doing that.
|
| There are lots of different groups looking to push heat
| pumps for the above reasons. Governments are concerned
| about both war and global warming. Ukraine supporters are
| concerned about Russia getting more money (to wage more
| war). Green activists are concerned about global warming.
| All have their own reasons to push heat pumps on
| everyone.
| oceanplexian wrote:
| An overlooked benefit is that they actually improve comfort
| over a boiler in a dry climate, so if you live somewhere with
| low humidity they help keep the air less dry. They also give
| you heating and cooling.. for places that don't have Air
| Conditioning it's a worthwhile upgrade.
| aintgonnatakeit wrote:
| Sorry but this is incorrect. Boilers aka hydronic heat is
| usually delivered through baseboard fin-tube or hot water
| radiators. These heat mostly through convection with some
| radiation. Any humidity in the house is retained. Forced
| air heats the air and removes humidity absent a humidifier.
| wittenbunk wrote:
| Neither removes humidity, only AC does that. All types of
| heating lower relative humidity by increasing the
| temperature of the air.
| sbradford26 wrote:
| Forced air doesn't remove humidity from the air either.
| Humidity is lost through air leakage in homes. Since the
| air outside had less absolute humidity in the air then
| humidity will drop due to air leakage. Most measurements
| of humidity is relative humidity though which changes
| with air temperature. So any system that heats air will
| reduce relative humidity.
| oh_sigh wrote:
| Sure, but you can get a whole home.humidifier for like $300
| to mitigate that issue.
| bruckie wrote:
| My parents installed a whole home humidifier a couple of
| years ago. It cost way more than $300 (closer to $2k
| installed--maybe they just got the wrong one?), and it
| also costs a lot to operate each month in additional
| electricity usage. Having a system that doesn't require
| one sounds much nicer.
| oh_sigh wrote:
| I got quotes in that range as well here in boulder, so I
| installed one myself a week ago in about 2
| hours(aprilaire 700 - $310) with no special HVAC
| knowledge, though I am mechanically and electronically
| inclined.
|
| I haven't checked the electricity usage but I can't
| imagine it is much. The system is literally just a small
| fan and a solenoid valve. Maybe your parents opted for a
| steam system, whereas mine is called a flow through
| style.
| [deleted]
| megaman821 wrote:
| I assume in home that don't have ACs, that they also don't
| have ducts. Do these ductless homes filter their air,
| control home humidity, or bring in fresh air from outside?
| wongarsu wrote:
| "Ductless homes" usually circulate hot water through
| radiators. If you switch to a heat pump, nothing's
| stopping you from circulating cold water in the summer,
| though obviously there is a limit on the temperature
| delta (you can heat water much more than you can cool
| it). Bringing in fresh air is a manual process (open the
| windows), and filtering air or controling humidity is
| then left to seperate appliances, if done at all. Though
| small fans to the outside for forced ventilation are
| gaining some popularity for giving you automatic air
| exchange and filtration.
| benplumley wrote:
| > nothing's stopping you from circulating cold water in
| the summer
|
| Condensation is - air conditioners have an integrated
| drip tray which drains to the outside, but if you ran
| chilled water through radiators they'd all make puddles
| of condensation on the floor. Retrofitting drains might
| be possible but I've never seen one and I can't imagine
| it'd be cost-effective vs installing mini-splits.
| sbradford26 wrote:
| There are many reasons why you can't just circulate cold
| water though a radiator to cool. As another commenter
| stated you will get large amounts of condensation. But
| the other reason is that you do not get nearly as
| effective of convection currents with cool versus
| heating. Your radiators utilize convection currents to
| circulate the warm air around the room. Running chilled
| water though the a radiator would be like having an ice
| cube in the corner of the room. It isn't going to cool
| the whole room down and will get water everywhere.
| ptmcc wrote:
| My ductless house has a gas combi water heater/boiler and
| hot water circulation system to in-wall radiators with
| simple blower fans.
|
| The house also has an exhaust fan on a timer, paired with
| small vents on several windows around the house, to cycle
| in fresh outside air. But practically for much of the
| year we just open the windows for fresh air since we live
| in the temperate PNW climate, wildfires aside :(
|
| I looked in to installing a minisplit heat pump system
| last year, but the quotes I got were outrageous ($25k+)
| plus as a retrofit it's not the most elegant integration.
| Someday I'd like to do the conversion and ultimately
| decommission the gas boiler, but at that price tag it's
| not happening soon.
|
| In the short term I bought one window AC and one portable
| AC for a combined ~$1000. It's not ideal but we only have
| a few weeks a year where cooling is really needed, and a
| few more where it's a nice luxury but not a necessity.
| trynewideas wrote:
| Maybe a faulty assumption; my AC-less home has a ducted
| oil furnace, and we still haven't removed the ducts after
| installing a heat pump. Another house I lived in 12 years
| ago had ducts for oil furnace heating but no AC. Both
| were 100+ years old and in the northern US.
| rootusrootus wrote:
| That matches my experience. All of our older houses
| around here with oil heat are forced air. Radiators are
| uncommon. But 'older' in this case is only 100-120 years.
| quickthrowman wrote:
| NG (in the US) is now about 70-80% cheaper than it was at the
| recent highs.
| brewdad wrote:
| And my local utilities just got approved for massive rate
| increases locking in those higher prices. Of course, I
| probably wasn't paying the full costs this past year.
| mytailorisrich wrote:
| It's not directly related to the recent spike in prices,
| especially considering that a heat pump installation is very
| expensive in itself and potentially disruptive.
|
| Rather, it's a combination wanting to get to net zero, so no
| emissions, with the big problem of generating enough green
| electricity. A heat pump system has no emissions and consumes
| much less electricity than an electric boiler/electric
| heater.
| Thlom wrote:
| I replaced my old air-to-air heat pump with a new one last
| year. Cost me in total around $3000-$4000. Might have been
| a bit more expensive if it was a completely new install
| depending on how it would be installed, but not too much
| more expensive. Might be more expensive in countries where
| you are using gas boilers as it sounds like your heating
| setup is much more complex than where I live.
| mytailorisrich wrote:
| Here in the UK, I think the cost of installing a new heat
| pump, bearing in mind that it's an installation from
| scratch, starts at about PS10k ($12k as today's rate) to
| several tens of thousands. A ground source heat pump
| (which seem to be the ones pushed by the gov?) is
| probably PS15k to PS30k if you can install one at all.
| Replacing an existing gas boiler, which is what most
| people have, is probably around PS2k or even less in
| simple cases. I had mine replaced 2 years ago with the
| new one installed on a different floor so a fair amount
| of plumbing was required, and it 'only' cost me PS3k.
|
| There are government subsidies but it's still much more
| expensive in the end. I think they are simply too
| expensive and impractical to install for most people.
| gambiting wrote:
| Which I absolutely don't get. I just had a mini split
| unit installed at our house here in North East, paid
| PS1500 total with installation, and damn that thing
| throws a lot of heat - I literally stopped using our gas
| boiler, it's more efficient(and cheaper!!!!) to use this
| unit for heating than to burn gas. It uses like 800W of
| power when running but produces ~4kW of heat.
|
| I imagine the "proper" heat pump costs a lot because it
| has to integrate into your central heating - heat and
| pump water etc. But I also imagine for a _lot_ of people
| in this country 2-3 mini splits like this one would be
| absolutely sufficient, wouldn 't cost a fortune, and
| would save them money(plus they can be used for cooling
| when needed).
| pjc50 wrote:
| I've just signed up to the Scottish government subsidized
| scheme for air source heat pumps, so I'll report back to
| HN on this.
| notacoward wrote:
| FWIW, I just installed two heat pumps in a 3100sf house
| in the US northeast this summer. We already had ducted
| AC. The main unit was US$17K and the mini-split for the
| master bedroom was US$6K. There a US$10K state rebate,
| but we'll probably only get 70% of that because we've
| retained the old heating system as a backup and for
| water, so total cost is US$16K. These are cold-climate
| units, both rated down to -4degF but I haven't actually
| made them work below 20degF yet. Next year I'll probably
| set the aux cutover temperature to something lower and
| see how it goes. Year after that we'll probably install
| solar (plus wind if the technology for that has moved
| along far enough) and switch to all-electric everything.
|
| BTW my town has an all-electric mandate for new
| construction already, and there's a lot of that. There's
| also a bylaw that takes effect in 2025/2026 banning gas-
| powered landscaping equipment.
| rootusrootus wrote:
| I think prices have spiked. Two years ago I installed a
| new heat pump to replace an old failing 5-ton air
| conditioner (which was paired with a high efficiency
| natural gas furnace; I kept the furnace as backup instead
| of relying on electric strips). It was $6K altogether.
| Was just going to replace the A/C with a new one, but the
| differential was $1500 and so I figured why not.
|
| OTOH, a few months ago my stepmother installed minisplits
| after getting quoted $22K to install a whole-home forced
| air heat pump (going from no forced air at all, so part
| of that cost was ducting, though it's a single story
| ranch house so not terribly difficult).
|
| Somewhere between those two points, prices went insane.
| bobthepanda wrote:
| They are also kind of a 2 in 1 appliance, in that they can
| run in reverse and cool your home, and are much more
| efficient at that than traditional ACs.
|
| In the US where AC is common, summer is generally peak
| electricity usage. I suspect this will become true in
| Europe as well with the heatwaves becoming a regular
| occurrence.
| rootusrootus wrote:
| > they can run in reverse and cool your home, and are
| much more efficient at that than traditional ACs.
|
| I'd love to see a source on that. There is very little
| technological difference between an air conditioner and a
| heat pump aside from refrigerant reversing valves that
| allow changing which end is the condenser and which the
| evaporator.
| Volundr wrote:
| A heat pump is an air conditioner that can run in
| reverse. Put another way, an air conditioner is a
| marketing term for a specific kind of heat pump. Your
| correct that there is no inherit efficiency different.
| Perhaps what was meant is that they are much more
| efficient than traditional resistance heating?
| Kirby64 wrote:
| I think as a general statement it's true, however the
| causal reason for that is not because they're heat pumps,
| it's because of the market for heat pumps is different.
|
| If you poll the current installed base for HVAC, I
| suspect you'd find that the (vast) majority of systems
| are minimum SEER rated (i.e., least efficient) systems,
| so SEER 13/14 (just became SEER 14 this year).
|
| In comparison, if you're already paying the premium for
| the heat pump system, likely you also pay an additional
| premium for a higher SEER unit. Also, what I've seen when
| doing some online shopping that most heat pump systems
| marketed seem to be higher SEER. Likely, because the cost
| associated with additional heat pump stuff drives into a
| higher end market where you 'might as well' make them
| higher SEER as well (with inverter compressors, variable
| fan speeds, etc).
| kebman wrote:
| Looks like the HN posting crashed the site.
| WatchdogReset wrote:
| The site is pretty new, I am the webmaster, maybe I should
| analyze the log and choose better hosting. I am sorry about the
| inconvenience!
| YellowTech wrote:
| Seems like OP just performed a stress test on his website as he
| is the "Webmaster of https://hvac-learning.com an HVAC elearning
| website"[1]. Hopefully you can figure out something! Thank you
| for educating about such technology!
|
| [1] from WatchdogReset's profile about
| WatchdogReset wrote:
| I am sorry for the inconvenience. I am still learning how to
| build a nice and efficient website. I will analyze what
| happened and try to fix and enhance !
| scrollaway wrote:
| I love that you're building free educational resources,
| especially about something like this! If you need help/advice
| to help build your website, email me (see my profile), I'll
| be delighted to help pro bono. :)
| spikej wrote:
| Genuine question that I haven't been able to find a clear answer
| for: are heat pumps now different from air conditioners two to
| three decades ago? (other than the fact that they heat and cool)
|
| Memory is fuzzy but I remember when I was a little kid and even
| captain planet cartoon showed air conditioners being bad for the
| environment...
|
| Or is it that heat pumps are better than the fossil fuel
| counterparts and so if you're going to do something bad you might
| as well do something less bad?
| Calvin02 wrote:
| It is the latter.
|
| Heat pumps are much better for the environment compared to the
| other sources of heating. Depending on where you live, you
| still need to heat your place and if so, heat pumps are better
| than other traditional methods like natural gas, wood, oil, or
| electricity.
|
| Similar to air conditioning, if you want to minimize your
| impact on the climate, you could set your temperature lower in
| the winter and put on a few more layers and/or set the
| temperature higher in the summer to minimize your usage of heat
| pump/air conditioner. This puts less pressure on the grid and
| demand for electricity generation.
| bagels wrote:
| Captain Planet is not a reliable source of information. Air
| conditioners use electricity, the generation of which can cause
| fossil fuels, but also can come from other sources.
| ccooffee wrote:
| > even captain planet cartoon showed air conditioners being bad
| for the environment
|
| That seems like it was a useful simplification for a children's
| cartoon, but things aren't that black-and-white.
|
| 1. Without air conditioning (or some other method of cooling
| and humidity control), almost all high-occupancy buildings
| would reduce their effectiveness as a work-place or living-
| place. OSHA has guidelines about office temperature (68-76,
| iirc), humidity, and overall air quality (e.g. pm2.5 levels).
|
| 2. The 1980s-era backlash against air conditioning was likely
| inspired by then-new knowledge about atmospheric ozone
| depletion. It was known that CFCs and bromine-containing
| compounds contribute to ozone depletion. It just so happens
| that CFC were common refrigerants (and aerosolizing agents).
| Refrigerant leaks from an air conditioner in those times
| released nasty stuff. CFCs are very rare (and restricted) in
| modern air conditioner / hvac systems. We instead use other
| chemicals which are not ozone depleters. (Though I believe that
| the theoretical performance of modern refrigerants is often
| not-as-good as the old CFCs.)
|
| 3. Running the air conditioner in a single family home is not
| terribly efficient, as (in most single family homes) most of
| the home is just empty space. Cooling bodies directly (e.g.
| cooling blankets, misting fans, etc) is more energy-efficient
| in these situations. Perhaps the more nuanced advice would be
| to use air conditioning to make the space "tolerable" but use
| direct cooling to make a space "comfortable". (This advice also
| applies to heating a space. I keep my thermostat between 60 and
| 65 and use blankets, small electrical resistance heaters, and
| drinking hot water as ways to temperature-regulate.)
| scrollaway wrote:
| Are cooling blankets a thing? Like, a not-a-scam thing?
| ccooffee wrote:
| I don't know how well they work. I have a sibling with one
| that they use frequently, but that sibling is a bit odd. (I
| think the blanket circulates water through it, but I've
| never really asked.) Their use may just be due to a
| placebo-esque effect.
| rr888 wrote:
| I just dont like moving parts. My problem with heat pumps is that
| you have to replace every 10-20 years which seems wasteful.
| kupopuffs wrote:
| Do you own a heater that has lasted more than 10 years?
| bluGill wrote:
| The furnace in my house is from 1970 and still works. I don't
| want to know how inefficient it is. (I just upgraded the
| insulation of the house, replacing the furnace is a future
| problem)
| asow92 wrote:
| As someone who lives in the northeast and has a 3600sqft home,
| I'm wondering how many heat pumps it would take to replace my gas
| steam boiler system. I'm not sure if heat pumps would be cost
| efficient given those parameters.
| elil17 wrote:
| One* heat pump will do fine, but you might need a low
| temperature heat pump depending on where you are. After you
| factor in that gas is cheaper than electricity per kWh, the
| system should save you money as long as it is running at an
| efficiency higher than ~130%.
|
| A contractor should be able to select an appropriate system for
| you, but if you want to do it yourself, look for yourself, get
| the 2021 ASHRAE climatic design conditions for your area and
| choose a heat pump with a minimum operating temperature which
| is lower than the coldest month 99.6% heating drybulb
| temperature (DB) (should be the top row, left most
| temperature).
|
| *You would also need a fairly large heat pump, perhaps 7 tons
| (tons here means tons of refrigeration, or how many tons of ice
| the system can melt per day) depending on how well insulated
| you are.
| prottog wrote:
| In the Northeast with that much square footage, you would be
| better off with ground-source heat pumps (whether open or
| closed loop), rather than the normal air-source heat pumps.
| asow92 wrote:
| I guess the concern I have with all this is that my current
| system works well, and I don't want to spend $10K+ unless it
| brings down my heating costs significantly. Could a ground-
| source heat pump system do that?
| prottog wrote:
| Like other commenters said, a GSHP will work excellently in
| terms of keeping you comfortable at a low ongoing price,
| but your initial costs will far exceed a $10k budget and
| you will likely never make that investment back ;-)
| zeroonetwothree wrote:
| It depends on relative prices in your area so we can't
| answer that. You would have to calculate it yourself.
|
| Typically it makes the most sense to do when you need to
| replace your system.
| sbradford26 wrote:
| Ground source/geothermal would significantly reduce your
| heating costs but it would be significantly more than 10k.
| For that large of house something like 40k+ wouldn't be out
| of the question, with the largest expense being drilling.
|
| I personally think geothermal is great, sadly New England's
| geography makes getting a ground loop installed more
| difficult. In the midwest lots of people would do a
| horizontal loop by trenching like 8 feet underground laying
| pipe in there. In many parts of new england that isn't
| really viable with all the rock so vertical drilling is
| used which is significantly more expensive.
| snuxoll wrote:
| My brother-in-law lives in NE and has installed mini-
| splits and has overall enjoyed them. A ground source
| system would be "the best" for that region, but if you're
| not doing a new build then air source works just fine
| there with the correct equipment.
| sbradford26 wrote:
| I also live in NE and we recently installed a mixed
| system. We have mini split units in the upstairs and a
| ducted air handler in the basement all attached to a cold
| weather heat pump outside. It has be working great for us
| so far, but we have the advantage of having a smaller
| house so we only needed one 4 ton unit outside.
|
| Our house was built in 1973 and originally had electric
| baseboards and then was converted to an oil boiler with
| hot water baseboard. So retrofitting a heat pump was an
| interesting task.
| mikeyouse wrote:
| What do you use to heat your water? If it's natural gas,
| it's likely close to making sense. If you use propane, it
| definitely makes sense to switch.
| endisneigh wrote:
| I wish, wish wish there was a portable mini split (not a portable
| air conditioner).
|
| The closest thing is this:
|
| https://rollibot.com/product/mini-split-ac-room-air-conditio...
|
| but it sucks.
|
| I don't understand why these things have to be permanent fixtures
| of your house, necessarily.
| timerol wrote:
| NYCHA is currently running a contest to develop a heat pump
| window unit. All of the proposed units are expensive to get
| those contest dollars, but should come down in price after.
|
| https://www.gradientcomfort.com/pages/products-air-condition...
|
| https://www.achrnews.com/articles/147122-midea-heat-pumps-to...
| ctroein89 wrote:
| I have two heat pump window air conditioners installed in my
| apartment, with cooling, heating and resistance electrical
| heating: https://www.frigidaire.com/Home-Comfort/Air-
| Conditioning/Win.... The problem is that the tech is so
| poorly advertised, that I had to double-check the specs on
| manufacturer's website that this model was, in fact, a heat
| pump. Most people don't know that heat pump window units
| already are an option.
|
| I'd love for NYC to mandate that ACs must function as heat
| pumps: the additional parts are cheap, and as America's
| largest market for window AC units, the NYC market would
| force competition for much cheaper heat pump window units.
| timerol wrote:
| I have seen units like that Frigidaire before, and can
| never tell whether it's actually a heat pump, or just an
| AC/resistance heat combination.
|
| Edit: Nevermind I'm an idiot. From the spec page of that
| unit: BTU (Cool): 11,000 BTU, BTU (Electrical Heat): 3,500
| BTU, BTU (Heat Pump): 9,900 BTU. Though the owner's manual
| mentions an extremely warm minimum outdoor temp: "The unit
| should be operated in a temperature range of indoor side
| 60degF - 90degF (16degC - 32degC), outdoor side 64degF -
| 109degF (18degC - 43degC)."
| scythe wrote:
| >I'd love for NYC to mandate that ACs must function as heat
| pumps: the additional parts are cheap, and as America's
| largest market for window AC units, the NYC market would
| force competition for much cheaper heat pump window units.
|
| This isn't great if you want a building with hydronic
| heating and forced-air cooling, which is really just the
| ideal form of both technologies -- hydronic cooling creates
| condensation, while forced-air heating smells bad and
| leaves you with cold feet.
|
| Also, I found that Home Depot's website tends to be pretty
| clear about which window units are also heat pumps.
| bilsbie wrote:
| I'm confused what you're asking for (and why) but it sounds
| interesting.
| endisneigh wrote:
| A portable machine to provide heat and cooling via heat pump
| technology.
|
| For cooling this exists in many forms: there are the window
| air conditioners, and "portable" window air conditioners
| which have a duct that connects to the window. The problem
| with the latter is that they're loud and the ducts result in
| a lot of heat loss.
|
| For heating there are some portable air conditioners that use
| a heat pump but they're subject to the same issue described
| above. More common is resistive electrical heat in the form
| of coils or an oil filled container that radiates heat.
|
| A portable mini split, where it connects through the window
| would give you a similar advantage as a portable air
| conditioner, but with more efficiency and being less loud.
| bilsbie wrote:
| Cool idea. So a two piece portable with a just coolant line
| going through the window to the outdoor part?
| endisneigh wrote:
| yeah, exactly. there's a company called MRCOOL that does
| something similar (https://mrcool.com/diy-4th-
| generation/), but the head (the indoor part that provides
| the heat/cooling) is designed to be mounted permanently
|
| if this were popular you'd see old houses retrofitted
| with pluggable holes where you could feed the lineset
| through and seal as necessary for temporary heat/cooling,
| or perhaps even permanent.
|
| the installation would be substantially easier if these
| were like 6000BTU instead of minimum 12000BTU per head,
| so it could be run on say, ~8 amps and be plugged inside.
| aaronax wrote:
| Coolant supply and return, both fully insulated. And
| condensate drain line, and power wires, and control
| wires. Do-able, but more complex than one might initially
| think.
| almuhalil wrote:
| There is a portable mini-split that recently came onto the
| market, and its form factor is similar to that of a window
| AC: https://www.gradientcomfort.com/
|
| The only problems I can see are:
|
| -Size/Price ratio: The tonnage (9,000 BTU) is relatively
| low for its price--it can only condition a ~375 sq foot
| space. Though the lack of install costs probably makes up
| for this unless you're doing a DIY job with a Mr. Cool
| Ductless HP.
|
| -Incentives: Utilities may not want to spend energy
| efficiency incentive dollars on these, since someone could
| easily move and take the heat pump outside of the utility
| territory; which is not a problem with permanent HVAC
| installations. Might be covered by the IRA's rebates for
| Heat Pumps though.
| sparsely wrote:
| I believe you are describing something like this:
| https://mrcool.com/u-shaped-window-a-c/ Never used one
| myself but they are meant to be much better than the ones
| with ducts - you don't lose so much efficiency from the
| ducts or from badly patched up window openings.
| scythe wrote:
| The issue is that cold should be supplied near the ceiling,
| while heat should be supplied near the floor. So this unit
| would need two separate terminals or suffer inadequate
| performance in one of the modes.
| WatchdogReset wrote:
| The heat pumps are one of the means of heating (and air
| conditioning) in the heart of the news. What is their principle
| of operation. You can ask questions here if there are points to
| clarify in the course
| jcstauffer wrote:
| I'd like to get a heat pump to replace my existing baseboard
| hot-water system (currently powered by an oil furnace) without
| converting to a heated air system.
|
| From what I've read, that's not quite feasible yet, since
| current systems can't produce a high enough temperature.
|
| What are the prospects of that technology becoming viable in
| the next few years?
| sokoloff wrote:
| Figure out the minimum flow (supply) temperature that can
| meet your building heat loss on the design day. If you have
| enough radiation, you might be able to get by with 135degF
| flow.
|
| I have baseboard in the attic and cast iron rads on the main
| level. I have the flow set to 126degF until the outside air
| temp drops below 30degF and then I increase by 2degF for
| every 4degF change in OAT. So at 2degF OAT, I have 140degF
| flow.
|
| That's enough to maintain temp in my fairly poorly insulated
| 1920s house near Boston. It's enough to slowly recover temp
| as well.
|
| 140degF is a stretch for air to water heat pumps, but you
| could reasonably use an A2W for most of the year and
| supplement with a 9kW (31KBTU/hr) electric boiler as
| emergency supplemental heat and use that a couple days per
| year.
|
| What killed it for me (and the reason I have a fairly new gas
| boiler installed) is the upfront cost was utterly
| uncompetitive.
|
| If you have a condensing boiler, set the high-limit or flow
| temp to 130-135degF and see how your house handles it on the
| cold days. You can measure and calculate all you want, but
| nothing beats trying it.
| WatchdogReset wrote:
| I think this is possible. I will ask to a teacher of hvac-
| learning and come back to you asap. But basically you can
| heat water instead of air with a heat pump.
| WatchdogReset wrote:
| As others comments said, it depends on the climate : The
| problem is that the power/performance of the heat pumps
| decreases with the cold weather and the necessary increase in
| the temperature of the heating water, which obliges to keep
| the boiler for the cold weather. This is a problem for the
| heat pumps without probable solution and little progress to
| wait. The solution is to insulate the house very well so that
| its needs can be covered by the heat pump with less hot
| water. Divide the losses by 2 at least.
| masklinn wrote:
| > From what I've read, that's not quite feasible yet, since
| current systems can't produce a high enough temperature.
|
| Is it because baseboard hot-water systems have limited
| exchange surface surface and thus need very high temperatures
| to do anything?
| mikeyouse wrote:
| Yep - exactly the issue. They've started shipping much more
| efficient baseboard systems which run at lower temps by
| adding more fins, adding CPU fans to increase heat transfer
| across the plates, etc. but the correct answer is to
| usually invest in air sealing/insulating the house which
| will require fewer BTUs in the first place.
| zacharybk wrote:
| It partially depends on your climate. I'm in Portland, Maine,
| so for us, we have a natural gas furnace with radiators, but
| they're heavily supplemented by a few heat pumps. For us, the
| temperature frequently gets very low in the winter, sub
| 10degF, and this is the point when heat pumps aren't as
| efficient. An ideal set up in a small home could be heat
| pumps running off solar and a woodstove for when it gets
| really really cold.
| LazyMans wrote:
| This guy is a great resource if you want to understand what
| goes into a proper A2W system install. In Europe, it seems by
| law they are required to do heat loss calculations to size an
| install. In the US, it seems to be a little more loose.
| https://www.youtube.com/watch?v=0IvGe4JZLSU
| mikeyouse wrote:
| I saw a video recently from a ... less sophisticated place
| in the US... where the HVAC installer literally held up a
| piece of paper from the street with different sized houses
| on it, and sized the HVAC based on which of the houses best
| "covered up" the actual house when looking through the
| semi-transparent paper. Just astonishing. No consideration
| at all for the build quality/insulation details, no
| adjusting for the distance from the road, just a "welp,
| this looks like a 3-ton job".
| LazyMans wrote:
| That's insane. Proper sizing is paramount, it's also a
| good way to surface that 5k in insulation improvements
| might be the better first step to consider vs installing
| a larger system just to keep up with losses.
| sbradford26 wrote:
| So CO2 heatpumps are starting to become available in the US
| which can run higher temperatures. But most likely the best
| option would be to switch to radiators that don't require as
| high of temperature to operate. Something like underfloor
| heating or panel radiators.
|
| The other option that is common in New England is to keep the
| baseboard oil heat and get mini splits. Then run the mini
| splits for heat and if they cannot keep up switch to the oil
| heat.
| hcknwscommenter wrote:
| What works for me in the northeast with an old house is a
| high velocity small duct air handler/distribution system
| (unico) coupled with a Bosch cold climate heat pump, with an
| oil furnace backup. This is forced air, so not exactly what
| you are looking for and I get that the heat from those
| baseboards is a better quality/less drying form of heat. I
| could upgrade to add a whole house humidifier to address this
| a bit. I use the heat pump most of the year, down to an
| outside temp of about 25F, although Bosch says I should be
| good down to 5F. The oil furnace runs basically Jan/Feb (but
| not as much this Feb as it's like 50F today). I've also
| extensively sealed/insulated the house (although there's
| always more of that to be done in an old house). It's a
| pretty good solution. I'd love for the air to water heat pump
| tech to work better, but I got tired of waiting.
| suoduandao2 wrote:
| Solar hot water would probably be a better fit for your
| situation.
| molsongolden wrote:
| Calvin (Segment) and Baker (Plaid) also recently put together a
| nice up-to-date heat pump info page and a heat pump vs. existing
| HVAC calculator.
|
| https://heatpumpshooray.com/ https://calv.info/heat-pumps
| beardyw wrote:
| Error establishing a database connection
| WatchdogReset wrote:
| The site is pretty new, I(admin) am not used to have lots of
| traffic. I will analyze what happened and chose better
| solution. I am sorry for the inconvenience !
| energ8 wrote:
| I have seen repeated claims of heat pump CoPs improving over
| decades. Can anyone summarize or provide links to what
| improvements are being made? Compressor technology? refrigerants?
| Fans to move heat? all of the above? Where is the path from here?
| LazyMans wrote:
| I can provide a likely incomplete summary of the improvements.
|
| Compressors themselves have gotten much more energy efficient,
| although I'm not sure the impact on CoP is all that great since
| and waste heat from the compressor is being deposited in the
| home anyway. Variable speed compressors are the most efficient
| you can get pretty much.
|
| Refrigerants have improved in someways, but not really in
| others. Since heat pumps could be running with exterior
| temperatures that are quite low, with the system under
| pressure, some refrigerant blends would have less than
| desirable vapor pressures leading to problems running in very
| low temperature conditions. For the most part, the changes to
| refrigerant blends have been related to their Global Warming
| Potential (GWP).
|
| Expansion valves are a very important piece of a refrigerant
| loop, these used to be fixed orifaces. Nowadays these are
| dynamic, meaning they can increase efficiency of the system by
| metering the flow based on system load and other
| characteristics. These are called TXVs or Thermostatic
| Expansion Valves. Electronically controlled expansion valves
| are now hitting the market further increasing efficiency.
|
| Finally there is the design of the interior and exterior coils.
| I dont think materials have changed much, but the surface area
| has changed. You may noticed a 2 ton unit from 1997 is about
| 1/4th the size of a 2 ton unit from 2022. More surface area on
| the coil for the exterior unit lets you extract more heat from
| the air without burning a ton of energy running the fan super
| hard.
|
| Interior air handlers have probably improved some as well,
| variable speed motors, etc. Variable speed really is nice
| because you can get much more consistent temperatures in the
| home and wont get blasted in the face with heat from vents when
| a regular system cycles on and off.
| Freestyler_3 wrote:
| refrigerants (though some regulations have negative impact on
| this), Optimizing (DC motors and computers with sensors
| figuring out what is the best setting), Absorbing waste heat
| from the process, Insulation, Materials that stay more clean or
| self clean.
| Bhilai wrote:
| Definitely a lot of posts about heat pumps on HN recently that
| this topic has piqued my interest but only to the point that I
| want to know if I can install one in my home. Are there any legit
| resources out there that can help me understand if heat pump is a
| right choice for my home based on Geo, type of home, sqft and
| other factors to consider before replacing current systems (two
| ACs and two furnaces?)
| kevstev wrote:
| If you already have a central AC system, a heat pump is more or
| less a drop in replacement. The heat pump becomes both your
| heat and AC unit.
|
| Heat pumps are now the most premium option on units offered by
| the well known names in HVAC- Trane, Carrier, etc.
|
| In terms of suitability for your climate, they should work just
| fine for most people- they start to struggle if you are in an
| area when temps get down to about 10 degrees Farenheit, though
| they improve in this area each year. Even if you live in an
| area that cold, there are options to mitigate this- leaving
| your current furnace hooked up to be turned on during those
| cold periods, etc. What it comes down to is it just gets more
| expensive if you live in these colder areas, but over time the
| energy savings should give you a return on your investment in
| less than ten years.
|
| My Air conditioner blew this fall, so I am actively in the
| process of getting bids for heat pumps.
| hcknwscommenter wrote:
| My $0.02 are that any competent and honest HVAC company will be
| able to walk you through the concepts of your home's
| heating/cooling load etc. and what size heat pump can meet that
| need, what it costs to run annually, and what incentives there
| are. It's not that hard. I would reach out to three highly
| ranked (or word of mouth suggested) HVAC co's and start the
| conversation.
| rapsey wrote:
| I guess they are a new thing in the US. In Europe installing a
| heat pump with floor heating is done for practically every new
| family house. It is the cheapest (for us) and nicest way to
| heat up your home. Though very few people build houses out of
| wood, unlike the US.
| timerol wrote:
| What climate zone are you in? (assuming US)
| https://learnmetrics.com/wp-content/uploads/hspf4-and-hspf5-...
|
| If you're in 1, 2, or 3, heat pumps are definitely the right
| option. In zone 4 or 5, newer cold temperature heat pumps are a
| good idea. In 6, 7, or 8 it's less of a sure thing, and you
| will likely want a backup source for the colder days.
| gwbas1c wrote:
| Generally, they can work anywhere in the continental US.
| (Assuming you live in the US.) If you're in northern NH, NY,
| VT, or Maine, you might want to keep your gas system as a
| backup. (New homes tend to have electric backup, but if you
| have an older home they just keep your furnace as backup.)
|
| I have a 3000 sqft house in MA with a heat pump as my primary
| heat, and an electric strip as backup. The heat pump goes into
| the ductwork for most of the house. I generally haven't had
| problems. (It did have to be adjusted because it was the first
| time the installer put one in.) I have solar and usually get
| 1-2 large bills in January and February, and then March and
| April are very cheap, if I get a bill at all. My "large"
| January and February are comparable to what I'd spend on
| conventional heat.
|
| Last weekend we had a "once in a century" cold snap down to -4.
| Most of the house was at temp, but one room fell to the high
| 50s. From what I've heard, plenty of people with conventional
| heat had far worse issues than a chilly room.
| kodt wrote:
| North Dakota and Minnesota are on average colder than the
| states you listed. I would also include Montana, Wisconsin,
| Wyoming, and Idaho as states where you should be concerned
| about performance in sub zero temperatures and have a backup
| heat source.
| robotpony wrote:
| Around Vancouver our heat pump has performed adequately even
| down to -15C/5F. This may be related to it being a deep
| ground loop geothermal setup (vertical instead of
| horizontal), and the type of building (concrete). We do have
| a gas fireplace as backup, but have not needed it at the
| temperatures we see in this corner of the world.
| gwbas1c wrote:
| I'm air based.
|
| When I built my house, I called around and it didn't sound
| like geothermal works very well where I live. I suspect the
| reason why I was talked out of it is because my yard is
| very rocky.
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