[HN Gopher] OpenERV
___________________________________________________________________
OpenERV
Author : graboy
Score : 747 points
Date : 2024-12-16 03:55 UTC (19 hours ago)
(HTM) web link (www.openerv.ca)
(TXT) w3m dump (www.openerv.ca)
| PittleyDunkin wrote:
| > clean outdoor air
|
| Is the air outdoor or clean? It can't be both!
|
| Marketing bullshit aside, this looks great!
| 20after4 wrote:
| That kind of depends on where you live. And this can be
| combined with air filtration.
| PittleyDunkin wrote:
| Definitely in some places, but is there a region where
| outdoor air is so clean you don't need this device?
| viraptor wrote:
| Almost any place away from cities. I've got AQI <30, down
| to 5 or so, almost the whole year for example. (Apart from
| during an occasional bushfire)
|
| Cities and industrial sites are the exception with bad air
| quality, not the default.
| cyberax wrote:
| That depends, really. If you have an inversion layer
| going, you can get pretty poor air quality in lots of
| locations because people use crappy wood-fired stoves
| that produce a lot of particulates.
| 20after4 wrote:
| That does happen occasionally where I live, last night
| for example. But it's only a single digit number of days
| out of a year. The rest of the time air quality is very
| good.
| vineyardmike wrote:
| To be fair, "cities are the exception with bad air"
| neglects the reality that cities _are the default_ for
| where people live. So the "air near people" is generally
| city air.
|
| That said, I live in SF and my AQI is usually <50. Not as
| great as 5, but we sometimes get down to single-digits.
| Cities don't have to have bad air.
| amluto wrote:
| The filtration is icing on the cake. You want an HRV or ERV
| in any location where you want heating or cooling for any
| non-negligible portion of the year so that you can have
| energy efficient fresh air.
| dzhiurgis wrote:
| I live in small town on NZ coast. Air is very clean.
| Mosquitos and neighbor's wood burners don't care. ERV is
| top 3 item in my house (other than induction cooktop and
| Japanese toilets).
| willvarfar wrote:
| (ok nodding to ERV and induction cooktops, but what is a
| japanese toilet and why are they better?
|
| Haven't heard of them from grand-designs and those kind
| of youtubers)
| kla-s wrote:
| - auto lid open and close - heated seat - water jet to
| clean buttocks with subsequent warm air blower - relaxing
| music speaker (to drown out your defecating sounds and
| get you started)
|
| just some ideas what some (public)/most (nice home)
| japanese toilets offer, which might be hard to come by
| anywhere else
| dzhiurgis wrote:
| > hard to come by
|
| They are $200-300 online. Not Toto quality, but plenty
| good enough.
| macrolime wrote:
| The ERV itself is for removing CO2, not dust. Especially in
| cold climates where houses are built to be as air-tight as
| possible, these are a necessity. Even if you lived in a
| forest cabin you'd want filters to prevent too much dust
| and pollen. I've got a dual filter on mine, HEPA and
| activated carbon filter. The HEPA filter removes dust and
| pollen. I've found that if I don't use the carbon filter I
| get higher than recommended levels of NOx.
| open_erv2 wrote:
| You can add a filter to the TW4, there is an adapter/kit.
| It's a hepa filter from a car cabin filter system design.
| You rarely need both anti pollen and also ERV, so you
| would take the heat exchanger out and just use the filter
| and fan. As for dust, I recommend a good pc fan filter
| based appliance, not putting the filter in the flow path
| of the ERV.
| jeroenhd wrote:
| Most people here just open a window when they want to air
| out a room. That said, that does waste a lot of energy when
| heating/cooling your home on cold/hot days, so ERVs and
| HRVs are used to get the clean air in without exchanging
| heat with the outside world too much. They're quite cheap
| and effective compared to just running normal ventilation.
| block_dagger wrote:
| I live near a ten lane highway. I prefer to keep the outdoor
| air out, and the indoor air filtered. I could see this being
| very useful for other dwellings though.
| amluto wrote:
| You are either already failing to keep outdoor air out or
| you are getting too little ventilation. What you want is
| something like this device with the H13 filter option.
| Maybe that plus carbon.
| positr0n wrote:
| Think of it this way, since you aren't dying of
| asphyxiation when you sleep at night, you're already
| getting some air exchange with the outside air.
|
| With an ERV you can control how much air you get, and put
| whatever filter you want in between the outside air and
| your room.
|
| In fact the fancier systems will let you overpressure your
| house by running the fan pushing in slightly higher than
| the air pushing out, ensure air only leaks out of your
| house not in.
| LukeShu wrote:
| Fairly standard language for describing what an ERV does.
|
| Low-CO2 outdoor air vs high-CO2 indoor air, if you prefer.
| Important for how air-tight modern energy-efficient
| construction is.
| throw4321 wrote:
| People breathe, so you need outdoor air to replenish the oxygen
| and get rid of the carbon dioxide. That's "fresh" air.
|
| Unfortunately, outdoor air has particulate and ozone pollution.
| Filtering it gives you "clean" air.
|
| In winter and summer, you also heat or cool the indoor air for
| comfort. If you just pump in outside air, you effectively also
| pump out the indoor air. This wastes the energy that had gone
| into heating or cooling it.
|
| These systems save that energy by transfering heat between the
| air that's getting pumped in and the air that's getting pumped
| out.
| 20after4 wrote:
| This looks really cool! I started to build something like this
| using thin square aluminum tubing but I never finished the
| project.
| danans wrote:
| The way I like to describe HRV/ERVs to people who don't know
| about them is:
|
| "Imagine you could open a window to get fresh air into your house
| and stale air out, but when you did so, most of the heat/humidity
| would stay in during the winter, or stay out during the summer,
| leaving you just the fresh air".
|
| In terms of the effect on environment inside a house, I usually
| say:
|
| "Imagine it's always a fresh-air spring day inside your house"
|
| This is a great project. One problem with ERV/HRV systems right
| now is that they are very expensive niche products. While this
| system doesn't achieve the extremely high heat recovery
| efficiencies of counter-flow units, the perfect is the enemy of
| the good, and this seems like it could be orders of magnitude
| cheaper.
| llm_trw wrote:
| Do you have a source explaining how these work?
|
| Naively allowing the air columns to thermally mix would result
| in the average of the inside and outside temp. So how does this
| do better?
| LukeShu wrote:
| Counter-flow heat exchangers. A parallel-flow heat exchanger
| would result in the average, as you say; but a counter-flow
| exchanger means that as the formerly-warm air gets
| progressively cooler, it is exposed to progressively colder
| air.
| llm_trw wrote:
| Duh, thank you for reminding me air flows in a duct.
| gwd wrote:
| I've got a counter-flow heat exchanger, but it looks like
| they're using a different design:
|
| > Each OpenERV TW4 module has a very quiet pair of fans,
| pointed in opposite directions, and a heat exchanger in a 6
| inch pipe, that goes through a wall. The hot, polluted air
| from inside goes out for 30 seconds, and the heat from it
| is stored in the heat exchanger.
|
| > Then, the fan reverses direction, moving clean air from
| outdoors to the indoors. On it's way in, it picks up that
| heat from the heat exchanger. This type of heat exchanger
| is called a regenerative heat exchanger, or less commonly,
| a regenerator. The kind shown in the video is a
| recuperative type, not regenerative. Recuperative types are
| what most people think of, consisting of a thin layer of
| material that separates two gas streams. Regenerative heat
| exchangers are different. They briefly store the energy
| while air flows in one direction, then release it when the
| air flow reverses.
|
| > The OpenERV TW4 modules are made to always work in pairs.
| One always sucks air while the other blows air,
| synchronized over WiFi. This should be done, or hot air
| would be pushed out from the building through the walls
| during the ingress phase, causing heat loss.
|
| https://www.openerv.ca/learn-more
| empiricus wrote:
| the intuition: if the 2 colums flow in the same direction,
| the final temp is the average. but if the 2 columns flow in
| the oposite directions it is posible to fully exchange the
| temperature
| IndrekR wrote:
| The direction of flow is reversed every 30s. The cycle is
| short enough that due to the thermal mass there is thermal
| gradient within the heat-exchanger. So it effectively works
| as counter-flow heat exchanger. Same principle (but
| continuous flow) is used in rotor ERV: https://en.wikipedia.o
| rg/wiki/Heat_recovery_ventilation#Ther...
|
| Heat exchanger there is usually an extruded ceramic grid
| (ERV) or rolled corrugated aluminum (functions closer to HRV
| than ERV)
| littlestymaar wrote:
| > most of the heat/humidity would stay in during the winter
|
| Getting rid of humidity in winter is the main reason why you
| want to bring fresh air in a house though!
| danans wrote:
| Not in cold climates where in winter the air outdoors is very
| dry. Heating systems in such climates often have integrated
| _humidifiers_.
| littlestymaar wrote:
| Then it just means that you're overventilating! We emit
| much more steam (through cooking and showering for
| instance) than we consume oxygen/emit CO2 so controlling
| the humidity is the main purpose of ventilation, air
| renewal comes for free as a byproduct of that.
| manmal wrote:
| My system doesn't over ventilate - we sometimes have too
| high CO2 in the bed rooms, but humidity is way too low in
| winters, sometimes below 30%. That means getting sick
| more often and having irritated airways at times.
| wilted-iris wrote:
| I have not observed this to be true. Ventilating enough
| to keep CO2 low means sub 20% winter humidity in multiple
| places I've lived.
| szundi wrote:
| The less co2 you have the less effect of air exchange
| does have. Also more co2 in air also decreases this over
| the decades.
| cwillu wrote:
| For reference, it is currently 84% relative humidity and
| -20degC outside where I live. This is about the same
| absolute humidity as 5% relative humidity at 22degC
| (i.e., inside).
| littlestymaar wrote:
| An all you need to bring that up to above 50% is
| 2cl/cubic meter of water!
|
| A sponge drying up in your kitchen sink is enough to
| raise your kitchen's air humidity by 10%. Shut down your
| ventilation and you'll see, you won't suffocate but
| instead you'll get mold starting to pop-up. Moisture is
| the reason why houses have ventilation system in the
| first place.
|
| As I said elsewhere in this thread, though, there's a
| problem with "dumb" ventilation systems though: they
| can't really adapt to big variations in outdoor
| conditions, and as such they tend to suck way too much
| air out of your house than needed during the cold days.
| crazygringo wrote:
| > _A sponge drying up in your kitchen sink is enough to
| raise your kitchen 's air humidity by 10%._
|
| That's simply not correct.
|
| I go through _liters_ of water a day with my two
| humidifiers just to try to raise humidity by around 20
| percentage points. In a small urban apartment that isn 't
| much bigger than some people's whole suburban kitchens.
|
| A damp sponge isn't going to do a thing, and I can't
| imagine where you would ever have gotten the idea that it
| would.
|
| Moisture is not the primary reason for ventilation,
| except above showers -- it's to prevent CO2 buildup along
| with other toxic gases like CO and VOC's.
| littlestymaar wrote:
| > I go through liters of water a day with my two
| humidifiers just to try to raise humidity by around 20
| percentage points. In a small urban apartment that isn't
| much bigger than some people's whole suburban kitchens.
|
| No surprise, that's because your water gets vented
| away...
|
| My brother had a broken ventilation for a whole northern
| England winter in a flat he rented (and the landlord was
| too busy fixing this shit up), he had massive humidity
| issues with fungi spores making him sick before he
| understood what the problem was, and he'd tell you how
| much discipline it takes in manually venting your house
| by opening the windows to keep things from molding!
|
| > A damp sponge isn't going to do a thing, and I can't
| imagine where you would ever have gotten the idea that it
| would.
|
| Hey you know what, just do the math by yourself, it's
| just one pV = nRT away ! But of course, this is assuming
| you're not removing all that water directly as it
| evaporates.
|
| > Moisture is not the primary reason for ventilation,
| except above showers -- it's to prevent CO2 buildup along
| with other toxic gases like CO and VOC's.
|
| Maybe have a look at your local building code and see how
| the ventilation requirements are made. I've refurbished a
| house by myself and I did just that, it turns out the
| regulations are built on water extraction, as CO2 won't
| realistically kill or harm you, CO only matters in
| kitchens if/where you have gas stove (and in my country,
| this is subject to additional ventilation requirements in
| the kitchen itself independent of the house's
| ventilation), and VOC are only a recent concern. That's
| also why there have been hygrometer to pilot ventilation
| for a while.
| RGamma wrote:
| Even with our cross counterflow enthalpy exchanger it can
| get somewhat dry in the bedroom in winter. The device in
| the OP would probably require an additional humidifier.
| jmb99 wrote:
| My house currently is sitting at 35% humidity while being
| very poorly ventilated (~900ppm CO2). In the summer, it's
| around 50% with the same level of ventilation. This generally
| has been the case everywhere I've lived; in the summer,
| you're cooling air, which (all else equal) increases the
| relative humidity of that air. In the winter, you're heating
| air, which decreases the relative humidity of that air.
| littlestymaar wrote:
| > while being very poorly ventilated (~900ppm CO2)
|
| Aren't you missing a zero of something? Because 900ppm
| isn't "very poorly ventilated".
| crazygringo wrote:
| It absolutely is poorly ventilated.
|
| I notice I'm not as mentally focused once it gets to 800
| or so.
|
| I have a CO2 monitor to keep it below 600 for
| productivity and concentration.
|
| Remember, fresh air is around 420.
| littlestymaar wrote:
| It's "less than ideal" level of ventilation, but it's
| also very far from "very poorly ventilated" (it's not
| even above the target level set by workplace regulation
| in my country, which is 600ppm above the baseline).
| torginus wrote:
| Isn't it the other way around? 50% humidity means that air
| contains 50% as much moisture as it, _at a given
| temperature_. Raising the temperature means that the air can
| now hold much more moisture.
|
| Bringing in cold air at 50% humidity, then warming it up to
| room temp makes the humidity fall, leading to dryer air
| indoors than comfortable.
| Notatheist wrote:
| Yep. Humidity will tank to 25% here in winter. I have two
| humidifiers fighting the HRV continuously when it gets
| cold. As I understand it an ERV controls moisture as well,
| but such a module for my system costs over $4000.
| littlestymaar wrote:
| But household activities like cooking, showering, drying
| laundry, or even just washing the dishes etc. generate tons
| of moisture, and this moisture is the reason why your home
| has ventilation in the first place: to get it out and avoid
| mold!
|
| There's a problem with "dumb" ventilation systems though:
| they can't really adapt to big variations in outdoor
| conditions, and as such they tend to such way too much air
| out of your house than needed during the cold days (and it
| also tend to be designed to suck cold air into dry room
| first, and get out from wet rooms, when you want it the
| other way round when it's very cold).
| crazygringo wrote:
| Not in the winter though!
|
| In the hot and humid summer you're definitely trying to
| reduce indoor humidity.
|
| But in the winter when it's bone-dry? A hot shower barely
| makes a difference.
|
| I keep two humidifiers running all winter long just to
| bring indoor humidity up to 35% or 40% where it's
| healthy.
|
| Otherwise it often goes down to 15% or even 10% on cold
| winter days, which is terribly unhealthy.
| littlestymaar wrote:
| > Not in the winter though!
|
| > In the hot and humid summer you're definitely trying to
| reduce indoor humidity.
|
| No, you can't do that with ventilation when it's hotter
| outside than inside actually, that's not how
| thermodynamics works! But we don't care about that,
| because in the summer you don't have cold walls or window
| where water vapor can condense and let mold grow.
|
| > But in the winter when it's bone-dry? A hot shower
| barely makes a difference.
|
| The reason why it doesn't make a difference is because
| all the moisture is vented away by your ventilation
| system! And that's because that's what it's designed to
| do! Stop it and see how it goes! For the record a single
| wet sponge drying up in your kitchen is enough to raise
| humidity by 10%! You barely need 2cL of water per cubic
| meter to have 50% humidity at 20degC.
|
| As I said the problem is that in winter, ventilation
| system often ventilate way too much.
|
| Also, they are often designed so the cold and dry air
| enters in the bedrooms/living room and the warm/moist air
| is extracted in the kitchen and the bathroom, and because
| of that the rest of the house doesn't get any of the
| excess moisture of these places. This is done because the
| designers wanted to make sure that the humidity level
| never raise too much in the room, because again humidity
| will ruin your house and health pretty quick (having air
| that's too dry isn't very good for your lungs, but having
| fungi spores in the air is much worse!)
| quietbritishjim wrote:
| I think you are agreeing with the parent comment with a
| tone of disagreement.
|
| They say they let cold air in during the winter because
| they want to lower the humidity.
|
| Then you say that, if you let cold air in (and then let it
| heat back up again) then you end up with lower humidity.
|
| The only thing you might disagree on is exactly what
| humidity you would like inside your house. But that's
| subjective. (As it happens, I agree with them: I often find
| it too humid inside during the winter, because I've
| restricted airflow to keep the heat in.)
| esskay wrote:
| Does very much depend on your location. In the UK a
| dehumidifier is still often a good idea in the winter because
| although our humidity drops, its nowhere near enough. Inside
| can still be high 50's, in older properties it'll never
| really go below 60%.
|
| Really a lot of our older homes shoud be retrofitted with a
| MVHR unit to help things as ventelation is awful in most
| houses. I'm actually quite surprised a lot of landlords in
| the UK don't do it as theres always a fight between them and
| their tenants who don't necesserily want to leave a window
| open all day in the winter to stop mold.
| ZeroGravitas wrote:
| Positive Input Ventilation (PIV) units seem to be a new
| thing for landlords to battle this problem.
|
| I think it basically trickles in cold (and therefore drier)
| air into a central space to reduce humidity, like an
| (slower, quieter) extractor fan in reverse.
|
| Seems a bit of a conflict of interest still, especially if
| the tenant is paying for heating.
| ZeroGravitas wrote:
| ERV is apparently the term used for HRVs that also exchange
| humidity and keep it in/out as required, though I'm not sure
| that makes much logical sense since E is for Energy and H is
| for Heat, no mention of humidity.
|
| Possibly just different terms used in different countries
| where the humidity is a bigger problem (very hot and/or very
| cold outside air).
|
| This current OpenERV product appears to use dessicants for
| this purpose but might be an optional add-on?
| mrspuratic wrote:
| A perfect ERV will recover the heat (occurs naturally by a
| temperature difference) and the latent heat (associated
| with condensation/evaporation). i.e. water vapour in the
| outbound flow should be transferred the inbound flow.
|
| This is to avoid energy loss that would occur when moisture
| condenses (i.e. the latent heat) by using an adsorbant
| material to capture moisture before it escapes, or a
| membrane that allows moisture in the outbound flow to pass
| to the inbound flow.
| colordrops wrote:
| I can't find anyone to install one in Los Angeles. Is there a
| particular climate these are suited for?
| jeroenhd wrote:
| Air exchange HRVs are quite common here in the Netherlands.
| Not exactly ubiquitous, but common enough that you can find
| them in most recently built apartments at the very least. If
| you're going to have mechanical ventilation installed, you
| may as well save a buck in the long run on the heat loss.
|
| There's only so much temperature gradient these setups can
| handle economically, and it's quite possible that the hot LA
| summers combined with the cool AC air are too much for such
| an installation not to leak energy at an unacceptable rate.
|
| Then again, just like with ACs that also serve as heat pumps,
| it could just be a matter of not enough people (or
| professionals) knowing about these installations to make it
| viable to build a business around them.
| TheSpiceIsLife wrote:
| HVAC folk ought to know about ERVs.
|
| Type in _HRV system_ in to your preferred search provider
| and hit the shopping tab.
|
| Here in Australia they range from about 1500 Antipodean
| Dineros for a single room through-wall mounted systems, and
| around 5500 upward for a centralised unit. Plus
| installation costs, but HVAC install is one of my paid
| activities, so I mostly don't pay that part.
|
| NB heat pump is a more accurate term for refrigeration type
| air conditioners, as in cooling mode they're 'pumping' the
| heat out of the inside environment and rejecting it
| outside.
|
| But have you heard about _brown_?
| driverdan wrote:
| That's surprising. Doesn't CA require them in new
| construction? All CA HVAC contractors should be familiar with
| them now.
| bluGill wrote:
| They have been required by code in all new houses in
| Minnesota for about 25 years. I'm sure CA requires them too.
| Though in older houses they are a waste of money as your
| house already leaks much air. These are a good thing if you
| have a well sealed house, but older houses universally are
| not sealed that well and so they won't give you anything.
| throw0101b wrote:
| > _I can 't find anyone to install one in Los Angeles._
|
| If you call a random HVAC company, they may not want to deal
| with "fussy clients" that want something "fancy" like an
| HRV/ERV. Best to look at folks that perhaps try to adhere to
| building science more. A quick search for the LA area:
|
| * https://www.jmsacandheating.com/indoor-air-quality/heat-
| ener...
|
| * https://www.aircomfortexperts.com/additional-products/ervs/
|
| * https://www.azaircond.com/indoor-air-quality/energy-
| recovery...
|
| * https://www.socalclimatecontrol.com/ervs-and-hrvs-energy-
| eff...
|
| Or do a dealer search from a manufacturer, e.g.,:
|
| * https://broan-nutone.com/en-us/home/dealer-locator
|
| > _Is there a particular climate these are suited for?_
|
| Any climate. Modern ones can even handle IECC Zones 6 and 7:
|
| * https://basc.pnnl.gov/images/iecc-climate-zone-map
| zerr wrote:
| To be fair, the temperature (coldness) of the outdoor air
| contributes to refreshing the room as well.
| d--b wrote:
| I don't think this is meant as a replacement for windows :D
| freetonik wrote:
| In Finland, many people avoid opening windows altogether,
| and only rely on various devices for mechanical movement of
| air. I find it quite alarming actually, as many homes have
| stale air and subpar ventilation systems, always justified
| by "never let heat escape the house". The idea of opening
| windows to refresh the air in the house is basically alien
| to many Finns, while it's a normal thing to do in other
| countries; in German, there's a term Stossluften.
| BlobberSnobber wrote:
| Stossluften isn't merely a term, it's a German religion
| pzduniak wrote:
| >that they are very expensive niche products
|
| My entire "medium sized European suburban house" runs on a
| $2.5k 400m3/h unit with HEPA filters made in Lithuania - and
| that was the more expensive model that I can directly control
| over MODBUS / 0-10V signal (even turning it into a "dumb"
| unit). Most of the expenses were running the ducts. YMMV
|
| It's just awesome. Every single room has fresh-smelling air and
| after fine tuning all my heating systems with algos implemented
| in Home Assistant - I'm getting ~60-100ppm over outdoor CO2,
| perfectly clean air, temperature within 1C of the set value,
| on-demand humidity extraction after showers etc. All it needs
| to be properly overengineered now is a bunch of dampers and
| per-room CO2/humidity feedback :)
| yrcyrc wrote:
| Would you have a link/reference?
| pzduniak wrote:
| https://www.komfovent.com/en/products/domekt-r-400-f-c6m-57
| 3
|
| I think this is the one I'm using for ~200-ish sqm.
| yrcyrc wrote:
| Great thank you
| tinco wrote:
| Anyone know if there's a good way to control 0-10V dampers? I
| looked for a solution to control 5 dampers but I didn't find
| anything, so I started to design my own a couple years ago
| but never finished the project. I'm having a hard time
| imagining something so common doesn't have a common solution.
| pzduniak wrote:
| If you're OK with large controllers, the cheap Chinese
| RS485 stuff seems to work perfectly fine. For "digital
| inputs" I started out with Polish $150 devices, eventually
| ended up using the cheapest AliExpress listings for some
| expansions and so far they've been working exactly the
| same, with the only difference being the quality of the
| docs. I'd expect the 0-10V modules to be exactly the same.
| karussell wrote:
| How is the noise of these systems? And how often/long need
| they run to give you clean air and humidity extraction. Is
| there extra noise when it is windy outside? Is it installed
| inside the windows somehow or do I need to drill through the
| wall?
| sgerenser wrote:
| Typically 2 holes, one for air intake and one for air
| outtake are drilled through the wall. They're often
| installed when a home is being built or heavily remodeled.
| They can be installed after the fact (especially if you
| have an accessible basement or attic) but it might be a bit
| invasive running ducts where you need them.
| ericd wrote:
| Alternatively, we got one piped into the HVAC ductwork.
| It's not as optimal as its own ducting, but it's much
| easier/cheaper than running a bunch of new ductwork.
| organsnyder wrote:
| That's what we did. Our house was built in 1916, but the
| weather sealing we've done combined with six people
| breathing in it led to quite high CO2 levels. We have a
| traditional ducted air conditioning system in the attic
| (heat is hot water radiant), and added the ERV there. It
| made a massive difference.
| michaelmior wrote:
| > after fine tuning all my heating systems with algos
| implemented in Home Assistant
|
| I'd be very interested in hearing the details of this.
| pzduniak wrote:
| I'll definitely prepare a longer write-up when I have
| everything figure out, but here's a summary:
|
| I have 4 systems:
|
| - Komfovent HRV for ventilation
|
| - NIBE F-series heat pump for floor and water heating
|
| - Vaillant gas boiler that "supports" the heat pump
|
| - Samsung multi-split AC units
|
| HRV - Komfovent uses the same controllers in all of their
| units, so you get all the communication goodies you'd want
| - though it took me a long while to figure out that basic
| features need to be toggled on :) There are existing YAML
| presets for their C6/C6M controllers on HA forums. The only
| caveat is that if you want to feed it a virtual thermostat,
| you need a stuff a device simulating a 10k NTC inside of
| the ventilator. Otherwise it's just a single Ethernet
| cable.
|
| Heat pump - I'm not exactly sure if I'm happy with NIBE,
| but thanks to the community the integration ended up being
| quite easy. I wasted a bunch of money on their MODBUS40
| just to learn that you need to use a certain MODBUS address
| in the internal bus to make certain registries writeable
| (eg. thermostat values) - so I took an ESP32 with Ethernet,
| a galvanically isolated RS485 dongle, a 12V to 5V converter
| and used https://github.com/elupus/esphome-nibe. The
| firmware extracts my templated HA sensor's value and feeds
| it to the heat pump as a virtual thermostat.
|
| Vaillant uses this weird "eBUS" protocol, there's a bunch
| of cheap PCBs that you can use to connect to it - I'm using
| https://github.com/danielkucera/esp-arduino-ebus. That's
| the last system that I haven't touched :)
|
| Samsung ACs use their MIM-B19N modules installed in the
| outdoor units. There's some magic around enabling remote
| control, but once you plug their diagnostics device into
| their indoor units, you can flash all of them at once. I
| had to mess around with internal NASA addresses to have all
| the units appear at once.
|
| For indoor sensors I have 3 types:
|
| - AirGradient units measure CO2, tempeature, humidity, PMx
| etc. - these are mounted at ~150cm and feed the "current
| house temperature" template.
|
| - I have like 8 Everything Presence One devices, powered by
| a custom PCB that converts 12V/24V sent over wired alarm
| cables to the device. They have built-in temperature,
| humidity and motion sensors. These are mostly installed for
| motion sensing and their height makes the temperature
| measurements quite useless.
|
| - Everything else (and most importantly bathrooms) is done
| using custom ESP32-C3 devices that use SHT31 sensors to
| measure humidity and LD2412 for movement sensing. Also
| using the same adapter PCB for powering.
|
| Thermostats are synchronized across all the devices with HA
| scripts. The HRV specifically uses its own wired
| temperature sensor to determine if it should enable heat
| recovery ("free cooling mode"), since its extracted air
| temp is always a bit lower than room temp (laziness :-)).
| "Current temperature" template fed to other heaters is
| derived from multiple room temperatures (currently using an
| average), with rooms "ignored" if AC is heating there (or
| was turned on recently). Ventilation has 2 modes set up -
| 20% and 80% - with the latter toggled by a bathroom
| humidity threshold.
|
| There are 3 remaining things I want to set up:
|
| - auto switching to gas heating if it's cheaper / the house
| is running on batteries - so far I've only imported
| electricity / gas prices into HA and quickly realized that
| I'm missing a power monitor on the heat pump circuit
|
| - dampening of air ducts to reduce the temp drop when high
| humidity extraction boost gets triggered
|
| - using more of the HRV range by auto-adjusting fan speed
| depending on real CO2 values - there's max 2 ppl at the
| house most of the time, so even at 20% the HRV is quite
| wasteful
| michaelmior wrote:
| Very cool! I think one of my biggest things is that I
| need my sensors to be able to manage things well.
| semi-extrinsic wrote:
| As a comparison for a "dumb" system, our house has a Nibe
| F110 that handles all air extraction and energy recovery
| (only for water heating) and a single Mitsubishi mini-
| split AC. And the bedrooms have some small electric panel
| heaters. I just cannot be bothered to fiddle with the
| smart house stuff, this solution works just fine for us.
| tomashubelbauer wrote:
| I wish this was as common as having a fridge in the house.
| The productivity gains from people not being sleepy and tired
| from shit air would be insane.
| tashoecraft wrote:
| When having my mini splits installed I pushed for an erv
| system in the bedroom. The installer had only ever done
| them in commercial units, and he hemmed and hawed about it,
| but I had two c02 monitors in my room showing it getting to
| above 2000 whilst sleeping. I've noticed a big improvement
| in how groggy I feel in the morning.
| BizarroLand wrote:
| If there were good enough ERVs that could be installed by
| the DIY'er for about the cost of a cheap refrigerator
| (~$600 or so) then they would be more common.
|
| I get that manufacturing the transfer plates isn't simple
| or cheap, but other than that one thing they're basically
| fans, they shouldn't cost that much.
| danans wrote:
| > My entire "medium sized European suburban house" runs on a
| $2.5k 400m3/h unit with HEPA filters made in Lithuania - and
| that was the more expensive model
|
| That is just the HRV, not the design of the system, the
| ductwork, and the installation. All those add up. In new
| construction those costs can be shared with the regular HVAC
| system design, but in a retrofit its far more expensive
| batushka5 wrote:
| These units are ubiquitus in northernish Europe, as any
| new/renovated building needs them to reach A/A++ energy
| effiency. Brands like Komfovent, SystemAir, offering 200 m3/h
| ducted units for 2000 Euros, with efficiency like:
| Outdoors degC -23 -15 -10 -5 0 25 30 35
| After unit, degC 12,9 14,5 15,5 16,5 17,5 22,6 23,6 24,6
|
| with indoor conditions + 22 degC, 20 % RH
| jonstewart wrote:
| Planning a renovation of my 1947 rowhome in DC, and I'm really
| looking forward to adding an ERV.
| bluGill wrote:
| You probably cannot do a renovation the tightens up your
| house enough to matter. Of course you have not specified what
| you are doing, it is certainly possible to do that, but it is
| a major effort that makes the house unlivable for a couple
| months and costs a lot of money. If you don't do that level
| of renovation your house will have enough leaks that a ERV
| will not make any difference in air quality (and even that
| level doesn't always make the house airtight enough to need
| an ERV). Making a house airtight is very hard - worth doing
| because of the energy savings, but not easy.
|
| If you are doing that level of renovation is is probably
| better to just tear down the house and rebuild. The costs
| will be similar and there are a lot of other things people
| demand of a new house layout that cannot be retrofitted in
| the old shell. Often the law will not allow this and so you
| are forced to renovate just to keep some now illegal feature
| that is worth keeping, but otherwise a tear down would be
| better.
| BizarroLand wrote:
| Anyone can do a renovation that "tightens up your house
| enough to matter".
|
| Use a qualified professional. Get multiple inputs.
|
| It will cost money, and more money as you approach
| perfection, but it is doable.
| bluGill wrote:
| Not really as the structrure of most houses leaks. It can
| be done but you are doing a lot of work that is easy to
| skip
| BizarroLand wrote:
| That is true, and I guess technically you don't want a
| house with no leaks, only with leaks that you have
| complete control over.
|
| Spray foam insulation can seal essentially any structure,
| and it doesn't require much more than a small hole
| drilled into the wall between the beams which is easily
| spackled over.
|
| It can also be put on as insulation in attics and
| crawlspaces.
|
| Combine that with a full ducting audit if any of your
| ducting pierces the envelope, a full intrusions audit for
| power boxes and the like, and new windows/house
| sheathing/ proper roofing, you can get very close to as
| good as a new built.
|
| Most of these I would not suggest doing as a DIY,
| therefore I still say it is expensive, and even moreso if
| you have lathe and plaster instead of more modern drywall
| or encounter any of a myriad of issues likely to be
| uncovered when doing these things to a very old house.
| throw0101b wrote:
| > _One problem with ERV /HRV systems right now is that they are
| very expensive niche products._
|
| Most building codes in US/CA mandate them since about 2015, so
| I'm not sure how niche they are (at least in new construction).
|
| Depending on the (air) volumes involved, ERVs can be had for
| under CA$ 2000:
|
| * https://gasexperts.ca/product-category/air-
| exchangers/lifebr...
|
| * https://bphsales.ca/collections/high-quality-erv-air-
| exchang...
|
| HRVs for less, but it's probably worth the extra few hundred
| for better humidity management.
| danans wrote:
| Installation is usually the most expensive part, and can
| easily send the total price into 5 digits of $, especially in
| a retrofit, depending on the market.
| turtlebits wrote:
| ERVs are not expensive, 1500 USD will get you a decent whole
| house unit. The installation is the expensive part, which this
| project doesn't change.
| kccqzy wrote:
| What makes outdoor air "fresh" compared to indoor air? You said
| that the temperature and humidity of indoor air are preserved.
| So is it just CO2 concentration? Would installing a chemical
| CO2 scrubber have an effect similar to an ERV system then?
| runjake wrote:
| CO2 and chemical off gassing from indoor items. Eg:
| manufacturing chemicals from furniture, natural gas, cooking
| fumes, etc.
| NavinF wrote:
| CO2 ppm is the main number that research studies look at, but
| it's also a proxy for the "freshness" of the air. All the air
| quality metrics are correlated. Eg a lot of cheap CO2 meters
| measure something else like TVOC and convert it to eCO2 using
| a lookup table.
|
| CO2 scrubbing would be better than nothing, but it's really
| expensive and won't improve other metrics like TVOC
| turtlebits wrote:
| You have it backwards. Counter flow units have lower efficiency
| than these "regenerative" type ERVs.
|
| The downside of this is that the high efficiency is limited to
| small spaces (based on the mass of your core), where counter
| flow units are great for entire homes.
|
| One point often overlooked with counter flow units, is that you
| can place exhaust ducts in spaces that you want to purposefully
| remove air, like bathrooms and kitchens, while providing fresh
| air to places with little air movement, like closets,
| basements.
|
| Regenerative core ERVs do little for fresh air circulation.
| brunoqc wrote:
| Is it safe? I think I heard that home made heat exchangers cause
| listeria or something like that. Something about condensation.
| danans wrote:
| IINM, listeria is usually spread by contaminated food, not air.
| dzhiurgis wrote:
| Probably meant Legionnaires. Melbourne recently had an
| outbreak when outdoor cafes used cooling towers (essentially
| mist sprayers) with some sus water -
| https://www.health.vic.gov.au/health-alerts/outbreak-of-
| legi...
| brunoqc wrote:
| My bad. Yes, I saw DIY heat exchangers posted in the past
| and people were worried about Legionella/Legionnaires and
| mold. It seems scary when we don't know what we are doing.
|
| DIY heat exchangers would be so awesome though. Only new
| constructions are required to have an heat exchanger here.
| ilyagr wrote:
| I'm confused how the heat retention could be around 80-90%
| without expending a ton of energy.
|
| Naively, if on average the same amount of air goes in and out,
| I'd expect the temperature of the heat exchanger (on average in
| space and time, eventually) to be the average of the outside and
| inside temperatures. If the outside is hotter, the air coming in
| would be cooler than the outside air (which is a win), but it
| couldn't be cooler than the average of the temperatures. So, it
| would still not be anywhere as cool as the inside air, which
| doesn't sound like 90% heat retention.
|
| Is the heat exchanger attached to a heater or a cooler? The
| linked video, https://www.youtube.com/watch?v=CDCu0IbEn8Q , would
| suggest not, as it talks about saving the energy needed for
| cooling or heating. Is there another clever trick?
| LukeShu wrote:
| Counter-flow heat exchangers can be very efficient, without a
| heater or cooler attached. That said, I don't think I've seen a
| commercial ERV claim to be more than 80% efficient, so I'm
| skeptical of the 90% measurement.
|
| (I've seen ERVs with heaters attached; but for the purpose of
| avoiding frost buildup when it's below freezing outside.)
| cyberax wrote:
| Commercial HRVs often use rotating disks, not counterflow
| heat exchangers. Disks are freeze-proof, but they need to be
| powered.
| cheeseface wrote:
| In my experience 80% plus is quite common in the models sold
| for colder environments. E.g. Mitsubishi electric Lossnay
| advertises 86%.
| snewman wrote:
| There isn't a uniform temperature across the entire exchanger.
| There's a smooth gradient extending from one end to the other.
| If the outside is hotter, then the inbound air gradually cools
| as it gives up heat to the outbound air which is gradually
| warming.
| cyberax wrote:
| > I'm confused how the heat retention could be around 80-90%
| without expending a ton of energy.
|
| Imagine two air streams counter-flowing. They "swap places"
| within your heat exchanger, so you can (theoretically) get 100%
| heat recovery.
|
| This principle is used by animals to minimize the heat waste,
| by counter-flowing warm and cold blood:
| https://en.wikipedia.org/wiki/Rete_mirabile
| danans wrote:
| Co-current flow (both flows moving in the same direction) work
| the way you described.
|
| Countercurrent-flow heat exchangers (where the two channels of
| the fluid/gas) move in opposite directions on both sides of the
| heat-transfer mechanism maintain a heat flow gradient over the
| entire length of the heat exchanger. This can result in an
| almost complete transfer of heat from one current to another.
|
| High efficiency HRV/ERVs use counter-current flow heat
| exchangers.
| singron wrote:
| What you describe is kind of like a theoretical heat exchanger
| that only averages temperature at a single point.
|
| You can improve this by exchanging heat across a continuous
| length along opposing flows. Imagine two parallel pipes
| thermally bonded where fluids flow in opposite directions. Each
| point still averages the temperatures, but the average
| temperature varies across the length and approaches the
| interior temperature on the interior side and the exterior
| temperature on the exterior side.
| ilyagr wrote:
| Yeah, I think this makes sense. If you connect many of my
| heat exchangers in series, the temperature gradient
| increases; only the middle one will work at the average of
| the inside and outside temperature (the example of 3 in a row
| makes sense to me). At the limit, it becomes what you
| described.
|
| Thanks!
| vanderZwan wrote:
| The mechanism described is called a countercurrent
| exchange. One fun detail is that it's quite commonly found
| in biological systems in nature too!
|
| https://en.wikipedia.org/wiki/Countercurrent_exchange
| open_erv2 wrote:
| It's actually a regenerative heat exchanger: https://en.w
| ikipedia.org/wiki/Regenerative_heat_exchanger.
| lsaferite wrote:
| The person you are replying to was discussing "exchanging
| heat across a continuous length along opposing flows",
| which _is_ countercurrent exchange. Regenerative exchange
| is, at least to my understanding, more of a cyclical
| store and release process.
| vanderZwan wrote:
| Yes, which is what OpenERV is. I can understand why they
| might have thought I was talking about their system, my
| wording was a bit ambiguous there. So it doesn't hurt
| that they cleared that up :)
| cies wrote:
| I'm not 100% sure about this. But with ERV (opposed to HRVs),
| iirc, also the moist of the air is transferred to the incoming
| air. The moist contains a lot of the energy.
| GistNoesis wrote:
| I find the idea of reversing the air flow direction every 30s
| simpler to understand than two counter-flowing pipe side by
| side.
|
| Imagine a pipe filled with 3 metallic grid sections (such that
| the air temperature in the section will equalize with the metal
| temperature) separated by plastic grids (such that the heat
| isn't conducted through the metal), and you push air
| alternatively from one hot side at 20degC to a cold side at
| 0degC for 30s and in the other direction for 30s.
|
| For symmetry reason, the pipe will passively (we don't count
| the energy required to move the air) have a gradient of
| temperature from the hot side to the cold side. The first
| section will be ~15degC, the second ~ 10degC, the third ~5degC.
| (Each section temperature is the temporal average of the
| temperature of the air flowing from previous sections : so
| because air switch direction, it means it's the average of left
| and right sections.)
|
| From the point of view of the house, you only lose energy from
| the first section of the pipe which will be more like 15degC
| rather than 0degC.
| nubinetwork wrote:
| Why can't I just glue a fan to an air filter?
| margalabargala wrote:
| That won't decrease CO2 or VOC levels.
| stackghost wrote:
| You could do this as an air purifier, but it will primarily
| just remove particulates and other HEPA-y things. It won't
| actually bring fresh outside air in.
|
| You could glue a fan to an air filter and then position the
| thing in a window, to bring in outside air that then gets
| scrubbed by the filter. But now you're bringing in cold air in
| the winter, or hot air in the summer.
|
| An ERV brings in fresh air and mostly solves the problem of
| having cold air rushing in on a winter day, or hot air rushing
| in on a summer day.
| jmb99 wrote:
| Air filters remove particulates down to some size, varying
| based on the filter. They do not scrub CO2 or CO, nor do they
| (generally) remove other things like VOCs - unless they're
| really, really expensive filters. Opening a window exchanges
| all that junk to be roughly equal to the baseline of your
| environment, which for most people is at least lower CO2
| levels.
| numpad0 wrote:
| Or open windows, but outside's cold in many places this time of
| the year. Energy recovery ventilators run stale outgoing air
| through a heatsink to pre-heat incoming fresh air to save
| heating costs. Sounds BS but it's a well established and widely
| used thing.
| dzhiurgis wrote:
| I've installed ERV about a year ago. It's great, but kinda
| overbuilt. The core is some very thin plastic film (some are
| aluminum). The body around it is 2mm metal. The entire device is
| 2-3mm metal. There are 2 motors inside that likely need good
| support, but not reason for this device to cost $1k and weight 30
| kg.
| littlestymaar wrote:
| What happens to the humidity in the outflow air when it cools
| down and condense?
| open_erv2 wrote:
| It condenses on the heat exchanger, then it evaporates when the
| airflow reverses direction. That's if you don't have sorbent.
| If you have sorbent, it gets grabbed out of the air before it
| can condense.
| ra wrote:
| I'm confused if this is true open source hardware and software or
| not?
| thanzex wrote:
| Me too, when reading "open source" I was expecting some design
| docs or the like. Aside from the general confusion of the
| website, I haven't been able to find some of the most important
| information. For example, there's no diagram or immediate
| explanation of the general working principle and airflow path.
| The heat exchanger itself is published only as-is for those
| designs, while the author writes that he uses a custom python
| script tuned for the design size and his 3d printer to generate
| it.
|
| When i saw this I immediately thought of studying it and reuse
| some of its designs for my custom use case, which does not
| appear to be currently possible.
|
| At first glance it appears to be "open source" in the sense
| that you can buy it, but if and when something breaks you can
| print/reorder it easily.
|
| Correct me if i'm wrong
| jeroenhd wrote:
| Under "source code", there's a link to a GDrive with a ton of
| design files and documentation, as well as source code.
|
| These are licensed CC BY-NC-SA 4.0, so depending on your
| personal definitions, they may or may not be "open source" (IMO
| they're open source but not FOSS but I've seen others equate
| open source with FOSS).
| open_erv2 wrote:
| As a community we need to do some thinking on how open source
| may sensibly be applied to hardware. Unfortunately Prusa, who
| used to be a real champion, has departed from the assumed
| True Path, and they have discussed their reasons, which are
| largely valid. That said their design at a more fundamental
| level has also departed from a maintainable, simple and
| elegant design.
|
| The purpose of the source code is to enable maintenance, not
| cloning, I say that on the website. That is this context,
| there are many others. It improves the economics because the
| machine lasts longer and there is no planned obsolescence.
| People are welcome to make their own units from the source if
| they have the skill, but although it would be fun, I don't
| really have time to make it easy. Some day there may be a kit
| which is very economical but it will still take a whole day
| of work to assemble, probably.
| toboche wrote:
| I don't think it's FOSS at the moment. I actually would build
| two or three of these units on my own and could provide some
| feedback along the way. My definition of open source means that
| I should be able to do so.
|
| Unfortunately, the gDrive files are not providing enough
| information for me to build one of these in a DIY manner. I
| didn't find enough information on the hardware side, no BOM, no
| hardware documentation. I think that, if the author would like
| to actually boost DIY adoption, it'd be worth having a step by
| step assembly guide. At the same time, when reading the page, I
| had a feeling like it's more supposed to be a way of
| advertising a future commercial product, not _really_ focusing
| on the FOSS /DIY side.
|
| The software is provided, but from my experience with such
| projects, it's maybe half of the minimum information needed to
| build a full fledged device.
|
| I like the project and would love to build it in the near
| future though.
| M2Ys4U wrote:
| No, it's not. Files are available under the CC BY-NC-SA licence
| which, because it does not allow commercial usage, is not open
| source.
| ltbarcly3 wrote:
| This is so cool!
| madduci wrote:
| Nice idea, but why do they use Google Drive for sharing their
| code?
| m12k wrote:
| Poor man's CDN?
| zo1 wrote:
| Or a very quick way to get your personal email address
| blocked. Pretty sure this will eventually trigger some sort
| of automated spam response and that account will promptly get
| blocked.
|
| Hope they used a throwaway google account with absolutely no
| link to his domains or main email address.
| gardenhedge wrote:
| I have a full system in my house. The unit is in the attic space.
| It's great although it makes a lot of noise, especially in the
| bedroom below the unit
| jsiepkes wrote:
| In the Netherlands these systems are fairly common in new houses.
| Mostly because the law mandates a certain level of energy
| efficiency of new houses. There are other ways of obtaining this
| required efficiency level, but an ERV unit is pretty cost
| effective.
|
| I've personally been looking at installing such a system [1].
| However since houses in the Netherlands are almost all made out
| of concrete installing such a system in an existing house is
| pretty hard.
|
| [1] https://www.duco.eu/uk-ie/products/mechanical-
| ventilation/ve...
| jacobgorm wrote:
| Same in Denmark, we pretty much had to install one when
| building our house, to make up for energy loss from the large
| window area we wanted. We didn't have it properly calibrated at
| first, but once that was (professionally) done it has worked
| perfectly and kept a pleasant indoor-climate ever since.
|
| The old-and-trusted brand here is https://www.genvex.com/en
| (ours was supplied by Ecovent though
| https://ecovent.dk/?lang=en )
| moooo99 wrote:
| Similar story here in Germany. New energy standards require a
| ventilation concept. Some people choose to rely on daily
| ventilation to save some money, but most people nowadays opt
| for an ERV. At least here in Germany, for some reason there are
| quite a lot of people who are super against the idea of having
| an ERV. Personally, I wouldn't want to miss is for having fresh
| air alone, not having to deal with pollen is an added bonus
| open_erv2 wrote:
| My basic understanding is that the thermal energy also costs a
| lot more over there than it does in north america, like 4x as
| much.
| ggeorg wrote:
| This sounds great! The site left me a bit confused however. Is it
| open in respect to software/firmware? Or also the hardware? Can I
| just build my own with stock components? Something was mentioned
| about a DIY kit... _The WM12 is basically two TW4 modules_ ...
| Um, TW4? As an ignoramus I need some introduction please...
| ensignavenger wrote:
| Apparently it isn't open source at all, firmware is CC BY-NC-SA
| 4.0. It appears that the author does not know what open source
| means.
| Hippocrates wrote:
| What's so good about fresh air? Like I don't want stinky stuffy
| air but as someone with central HVAC I had no issues with my
| indoor air. Are we trying to get outdoor smells? Or is it
| something else?
| Slurpee99 wrote:
| Possibly could help with radon poisoning
| ghosty141 wrote:
| In the winter it's cold outside and opening the window cools
| down the room -> no ventilation most of the time.
|
| In the summer it's not a problem for me, I leave my windows
| partially open all the time but in the winter especially when
| working from home this would be quite neat. Also, I live in a
| small town in germany so the air quality here is comparatively
| good to many of the city folks here.
| reubenmorais wrote:
| High CO2 levels impair cognition and stale air accumulates
| pathogens, not just smells. The V in your HVAC stands for
| Ventilation, so you're already getting fresh air, that's
| probably why you have no complaints. If you live in an air
| tight apartment with no forced circulation where CO2 levels
| spike super fast requiring ventilation several times a day,
| it's a different story.
| wtcactus wrote:
| I'm not understanding if it also filters the outdoor air coming
| in.
|
| I live in a place where supposedly the air is of good quality,
| and yet, when I open the windows, the all place gets a thin film
| of black dust on all surfaces - most probably due to the particle
| emissions and tire degradation dust from vehicles from the
| highway nearby.
|
| The solution I've found is to open the windows every day for
| about half an hour and then put an air purifier to work.
| londons_explore wrote:
| it appears the air filter is an optional extra, but
| incompatible with the storm vent.
| open_erv2 wrote:
| The filter is a bit messed up right now, you can put one on
| the TW4 but not the WM12.
| torginus wrote:
| This looks wonderful, but it operates on the assumption that
| outdoor air is something you'd actually want to breathe where you
| live :)
|
| Unfortunately, due to cars and dirty heating systems around where
| I live, outdoor air tends to be not great.
| alextingle wrote:
| How does it avoid short-circuiting when the supply and exhaust
| vents are so close together?
|
| There's lots of text on that web-site, but details of the actual
| design of the thing are pretty scant.
| MichaelRazum wrote:
| Looks interesting. Especially since it seems to be much cheaper
| that the closed solutions...
|
| Have looked in this kind of systems, for my parents. The use case
| was basically, not about energy efficiency, but rather noise
| protection - to be able to sleep with a closed windows. I think
| so far I always had two issues (in that usecase).
|
| - First the device by itself - produces a bit noise like 42db
| might be too much for some people if you want to sleep.
| Especially some of the devices are using one ventilator, which
| switches directions and won't produce homogeneous noise.
|
| - Second 60 CFM is fine, but if you want to have the feeling of
| an open window - it should be much more and most devices can't
| deliver that. Also the heat exchange thing is kind of cool in the
| winter for sure. In the summer, you often have the case that in
| the evening you house is much warmer than the air outside - so
| you would like to turn the heat exchange off in the winter.
|
| PS: Actually, maybe looking for a complete different use case.
| But I think what would be very cool, would be some idea to make
| at least one room 100% quite (with fresh air ) in a cheap way.
| Guess this would be a huge life changer for a lot of people, who
| suffer from noise pollution.
| leoedin wrote:
| I think that summer/winter distinction is really important. In
| the UK where most houses don't have air conditioning, you
| really don't want heat recovery for 1/3 of the year. On really
| hot days you might want to use heat recovery during the peak
| few hours, but otherwise you are trying to cool the house down
| with colder outside air.
|
| I would love some sort of intelligent house ventilation system
| which could do all that. Heat recovery when it makes sense,
| normal ventilation when it doesn't. All automated based on dT
| and relative humidities.
| ZeroGravitas wrote:
| I think with this model you can do this as long as you
| install them in a synced pair (which I think is the baseline
| assumption).
|
| Normal (heat recovery mode) you have them reverse flow every
| 60 seconds or so to swap heat.
|
| In cooling mode you just run then continually. One is
| bringing in fresh air and the other is removing stale air.
|
| The heat store in the intake will soon cool to the outside
| temp and the heat store in the output is irrelevant (apart
| from maybe slowing the air flow and creating noise).
|
| If you manually control the system you could combine with a
| few open windows to create cross breezes even on still
| evenings.
| 4gotunameagain wrote:
| That is very nice, and I really appreciate that the design files
| are open source.
|
| Great work.
|
| I cannot help to wonder what brings the total cost to $600, the
| price of a modern, powerful computer.
|
| And yes, I am familiar with the economy of scale :)
| londons_explore wrote:
| Looks to me like a low cost version of the same could be
| designed with 2 CPU fans ($1), and a large 3D print ($1 - for
| the DIY version) or injection moulding for a commercial version
| ($0.30). Do time-sync between the units with grid frequency
| sampling (free), and have the whole thing controlled by a 2
| cent microcontroller and a pair of triacs.
|
| The whole thing, designed and made in China could probably come
| to a BOM under $4, and retail in the USA for $12.
| 4gotunameagain wrote:
| While I agree with your points, $0.30 for injection moulding
| would need quite the scale, and I have doubts about whether
| two CPU fans would have enough power to flow enough air even
| in the absence of a HEPA filter.
| londons_explore wrote:
| Injection moulding is cheaper than you imagine now. The
| cheapest moulds start from about $250, and there are plenty
| of companies who will make a mould and make and ship 5k
| parts within 7 days.
|
| These designs would need quite a few changes to be
| injection moulding compatible - for one thing the fins are
| probably going to have to be flat not circular due to draft
| angle requirements.
|
| Changing the core to a roll of embossed steel foil might be
| a better bet, and whilst that would add about $1 to the
| price, it would also make the product work better and be
| more compact or more efficient due to a higher thermal mass
| in the core.
| 4gotunameagain wrote:
| Got any links for the $250 moulds and companies ?
|
| Maybe I could use them in my own project :)
| londons_explore wrote:
| Send these guys a message:
|
| https://zhongshengmould.en.alibaba.com/
|
| Never pay for a mould to be made with plans to ship the
| mould itself to another manufacturer - it's a common
| scam. Always make mould+make parts as a single
| transaction.
| 4gotunameagain wrote:
| thanks !
| open_erv2 wrote:
| Look up the price of a blauberg Vento or a Lunos e2. They are
| ~$1800 CAD, and they get a fraction of the airflow. Computers
| have a large ecosystem behind them and have been in development
| for a very long time. This is still at the start of the
| deployment curve.
| 4gotunameagain wrote:
| This has not answered my question. I can also come up with
| many examples of things that are expensive.
|
| What does really inflate the BOM ?
|
| And this is in no way to discount your effort or your
| results, I'm genuinely curious.
| funsi wrote:
| You get similar ones from alibaba from around $175 :
| https://www.alibaba.com/product-detail/Fresh-Air-Ventilation...
| kennethh wrote:
| What would be the advantage compared to commercial products like:
| https://les.mitsubishielectric.it/en/products/ventilation_37...
|
| This product cost around 500$ and also has heat exchange. A
| friend of mine has installed it and is very happy with it.
| open_erv2 wrote:
| It's better compared to a blauberg vento or lunos e2. That
| product probably gets poor efficiency, I have not checked the
| technical sheet but if they say 80% that means at the minimal
| flow levels, which are only 10 cfm or something. The TW4 gets
| >85% sensible and comparable latent efficiency, at 60 cfm. It
| also has twice the maximal flow of that device. It's got many
| other features as well, and is more durable. Ultimately, it's
| about return on investment. You have to make a spreadsheet and
| see which one is best, given the actual tested values for
| efficiency flow, maintenance cost, etc. If that's not possible,
| it's a shot in the dark.
| teekert wrote:
| I so need this, and I so need it to function with Home Assistant.
| I would love to ventilate based on values of my Aranet 4 (a
| bluetooth CO2 sensor). Also, would be nice if it coordinates with
| multiple units, ie what this brand does: [0]
|
| EDIT: It does, if you click on "learn more", you'll learn more:
| _" The OpenERV TW4 modules are made to always work in pairs. One
| always sucks air while the other blows air, synchronized over
| WiFi. This should be done, or hot air would be pushed out from
| the building through the walls during the ingress phase, causing
| heat loss."_ ...Perfect!
|
| Currently I have two holes in my wall for ventilation, when it is
| windy it's too much (feel the wind blowing inside), when some
| people visit and there is no wind, boom, >3000 ppm CO2 in 20
| minutes.
|
| I just really hope it is very quiet, although it says ~37 dBa
| (which is quite a lot imho), I replaced my bathroom ventilator
| recently, it produces 25 db! [1]). The previous one [2] produced
| 52 dB (cheapest around), that was pretty annoying, you'd hear it
| in the bedrooms above the room it was used in. Maybe 37 dB it
| isn't so bad, especially since you can wind it down and mostly
| need it when it's busy/noisy (many people) anyway.
|
| Btw, don't buy a CO2 sensor, pretty soon you're a ventilation
| nerd, or as my wife would call it, a ventilation curmudgeon.
|
| [0] https://blaubergventilatoren.de/en/series/vento-
| expert-a50-1...
|
| [1]
| https://www.filterfabriek.nl/ventilatoren/badkamerventilator...
|
| [2] https://www.hornbach.nl/p/rotheigner-toilet-
| badkamerventilat...
| Y_Y wrote:
| > One always sucks air while the other blows air, synchronized
| over WiFi. This should be done, or hot air would be pushed out
| from the building through the walls during the ingress phase,
| causing heat loss." ...Perfect!
|
| Absolutely.
|
| > A room is not heated by increasing its internal energy but by
| decreasing its entropy due to the fact that during heating, the
| volume and pressure remain constant and air is expelled.
|
| https://pubs.aip.org/aapt/ajp/article-abstract/79/1/74/10418...
|
| The point about balancing airflow is crucial, but I think
| underappreciated by non-professionals. Thermodynamics is highly
| non-intuitive in places, and the enclosed climate-controlled
| spaces we love to inhabit are certainly included in that.
|
| Don't get me started on the idea that you can cool a closed
| room by running a fan or opening a fridge.
| teekert wrote:
| _Don 't get me started on the idea that you can cool a closed
| room by running a fan or opening a fridge._
|
| Oh man I had this discussion with my wife yesterday, we have
| a small electric heater in a room where a pipe burst and I
| still need to fix that (no heating means instant fungus
| problems). It keeps its fan rotating always, that way it
| determines the input temp for its thermostat more accurately.
| But wife insists it is sometimes blowing cold air and thus
| very very bad... I explain what a thermostat is (bimetals and
| all) and that she experiences "coldness" because a layer of
| warm air is blown from her skin, it's not blowing cold air...
| she doesn't follow... I even measure the energy usage and the
| thing only uses 20 W or so when just blowing, not heating.
| Even when just blowing it's moving cold moist air from the
| walls so overall good. It's difficult dealing with her like
| this.
|
| I'll pay someone to tell me how to deal with someone like
| this and maintain a positive atmosphere. The thing is, I also
| do it for things that really are probably not worth
| discussing... I should pick my battles better, is there ever
| a good time for some mansplaining? Or should I say...
| Nerdsplaining?
| sneak wrote:
| The problem as it stands now is that she is experiencing
| something ("it is blowing cold air") and your claims ("no
| it's not") run counter to that direct experience.
|
| Place and leave a thermometer in front of it and give her
| the information that you are using to make your own claims.
|
| You went through a process to learn that moving air feels
| colder than still air at the same temperature. It seems
| that perhaps she has not. Surfacing the ground truth of the
| air temperature may help the situation.
| teekert wrote:
| Full of enthusiasm I did this whole thing as they did in
| Veratasium [0]. Didn't impress anybody in my family.
| Although my son is getting there I think... Maybe I'm
| just too bad and lengthy at nerdsplaining.
|
| Actually, I didn't put an ice cube on the metal, that is
| the trick. of course.
|
| [0] https://www.youtube.com/watch?v=vqDbMEdLiCs
| vanderZwan wrote:
| > _Don 't get me started on the idea that you can cool a
| closed room by running a fan or opening a fridge._
|
| On that note, I'm curious if hybrid heating/cooling solutions
| will ever take off. Other than this OpenERV product I mean,
| which I guess technically counts!
|
| Low Tech Magazine mentioned some experiments in their article
| on compressed air energy storage (CAES). Instead of trying to
| make that form of energy storage an adiabatic process, the
| idea is to use the heat produced/required in the
| compression/decompression steps in the household to improve
| the energy efficiency (e.g. use heat produced during
| compression to heat water; do the decompression in a space
| that should be cold anyway like a basement used for food
| storage).
|
| [0] https://solar.lowtechmagazine.com/2018/05/ditch-the-
| batterie...
| salomonk_mur wrote:
| 37dba is practically nothing. Like a very soft whisper from a
| couple meters away. Remember the scale is logarithmic, 37 is
| almost 2 orders of magnitude below 52.
| open_erv2 wrote:
| Thank you, this is correct. Using my class 2 sound meter, if
| I stand in my house in nowhereland cornwall with power shut
| off to the whole house, it's 38 dBa. 37 dBa is audible in
| that environment but nearly inaudible in a normal environment
| where your computer cooling fan is making 45 dBa at 1 meter,
| etc. 42 dBa is pretty quiet too, my furnace makes 43 dBa at 1
| meter from the duct when it turns on. And that 42 dBa is a
| full 60 cfm, full blast. That's more than twice the airflow
| of competing units like the blauberg vento. You don't turn it
| up that high when you are sleeping.
| teekert wrote:
| Ok, so that 25 dB fan is a lie then because it can very
| easily be heard over other noise.
| pzduniak wrote:
| Check out Komfovent units if you want a ready solution. My
| setup is Komfovent HRV (over MODBUS TCP), NIBE heatpump (over
| MODBUS UDP + esphome-nibe), Vaillant gas boiler (over eBUS-
| WiFi) + a bunch of AirGradients scattered around the house.
| Nothing has access to the internet, everything is glued
| together with HA. Works surprisingly well :)
| ZeroGravitas wrote:
| There's some comments here suggesting that the incoming and
| outgoing air pass each other in a heat exchanger. But this is a
| different model that passes he two streams in turn through a heat
| sink:
|
| > Recuperative types are what most people think of, consisting of
| a thin layer of material that separates two gas streams.
| Regenerative heat exchangers are different. They briefly store
| the energy while air flows in one direction, then release it when
| the air flow reverses.
|
| I have to admit I am slightly more dubious about this type as
| they are new to me, though I did see a YouTube video about a
| commercial one recently and they seem to be a hot new thing.
|
| Possibly this is something sensible that only becomes practical
| with software and wireless communication? Rather than running
| ducts to a central location.
|
| Though then fitting two side by side in a window seems odd. Why
| not use the traditional type in that case?
| mrspuratic wrote:
| I have two equivalent regenerative commercial units (HRV, no
| vapour handling) fitted at opposite sides of a mostly open plan
| ground floor. They use a heavy ceramic core, and sync for
| opposite or coordinated flow (optional). They go up to 60m3/h
| (~35CFM) which is extractor fan level for me, 60CFM (~100m3/h)
| is quite a step up. They were under EUR200 a unit about 18
| months ago.
|
| They are rated 90% recovery at low speed. Today it's 11C 75%RH
| outside, 18C 65%RH inside, at low speed (15m3/h rated at 1.2W)
| there's barely a difference: 17.8-17.9C air intake temperature.
| They keep the air noticeably fresh, drier and also keep the CO2
| down (<600ppm right now). I'm running them below the
| "recommended" 50% air-change per hour (ACH about 35%), and
| boost when needed.
|
| There's a recuperative ducted type in the attic for the first
| floor, when I checked last month it was 4C outside, 18C at the
| outlet vent, and 17C at the inlet vents. That runs at 50% ACH.
|
| The reasoning for the paired up window model isn't obvious,
| maybe a simple increase in capacity. The website is quite clear
| you need a push/pull pair to be efficient, and an immediately
| adjacent such pair is not going to work so well.
| xnx wrote:
| Great project. Hrv and erv should be a lot more common. Is there
| a diagram of the airflow in that unit? It looks like the intakes
| and exhaust on both sides might be very close to each other.
| londons_explore wrote:
| So, this doesn't use a traditional heat exchanger. Instead it
| appears to "pulse" air inwards then outwards through a series of
| fins.
|
| It effectively heats the fins slightly in one direction, then
| cools them again slightly in the opposite direction.
|
| Same with wetting and drying for recovering moisture.
|
| I am surprised that the fins appear to be plastic - one would
| imagine that steel fins would have far better thermal capacity
| londons_explore wrote:
| Less "open" than the name suggests, because the design is for non
| commercial use only, yet this is very much the kind of product
| that needs to be sold to see widespread adoption.
| sesm wrote:
| Mass market product would have a different design, intended for
| manufacturing at scale. This design is intended for DIY, mass
| producing with DIY-intended design is too expensive (see
| Ergodox as an example).
| boomskats wrote:
| I was reading up on counter-flow heat exchangers a few weeks ago
| after I'd just installed a MVHR system and realised that the
| actual heat exchanger components themselves were, counter-
| intuitively, a fraction of the price of the whole unit.
|
| I was surprised when I saw they're mostly made of thin plastic
| and don't depend on thermal capacity at all (unlike, say, HX
| espresso machines). The way they work is quite simple:
| c w
| o a |
| | l r
| +-----------------------------------------------------+ d
| m
| air at 50 deg ------------------------> air now 5 deg o
| i u
| d ---+--+--+---- heat exchanging surface-----+--+--+----- t
| o -- V V V ------------------------------- V V V ---- d
| o o
| r air now 45 deg <-------------------------air at 0 deg o
| r a
| +-----------------------------------------------------+
| i | | a
| r i
| r
|
| It's just a bunch of thin parallel channels where warm and cold
| air flow in opposite directions, separated by thin plastic walls.
| Because the flows are counter to each other, there's always a
| temperature difference driving heat transfer across the dividing
| walls, even as the warm air gradually cools and the cold air
| gradually warms.
|
| The lightweight plastic walls are advantageous here - while
| plastic isn't particularly conductive, the walls are so thin that
| heat transfers readily. It's how these heat exchangers can
| achieve 80-90% efficiency without needing any expensive materials
| or thermal mass. The warm exhaust air leaves only slightly warmer
| than the incoming cold air, having transferred most of its heat
| to the incoming stream.
|
| Clever design.
| ent wrote:
| Thank you for the illustration! I was sitting here, wondering
| that the whole system sounds paradoxical but seeing it drawn
| down with the arrows really helped grasp how this works!
| turtlebits wrote:
| Not sure what you mean by the heat exchanger core being a
| fraction of the price, but I've seen replacement cores cost
| around 1/3 of the total unit.
|
| They should be made of high thermal conductivity material like
| resin or ceramic.
| mreiner wrote:
| Cool project! Around that topic I can also recommend a channel of
| this engineer (switch to auto-translate):
| https://www.youtube.com/watch?v=Cv0s6TgwbJg
|
| Paraphrased:
|
| - push-pull ventilation is easy to install and comparatively
| cheap
|
| - it's prone to hygiene issues like blowing dirt out of the
| filters back into the air and providing a moist environment for
| microorganisms in some operational conditions
|
| - it's prone to windy conditions
|
| - the numbers stated by commercial vendors seem to have no basis
| in reality, there seems to be no vendor providing data based on
| the relevant testing standard for these systems. OPenERV states
| they want to get it tested by Passivehause institute but also say
| no lab data measured yet.
|
| Might be just my counter-factual gut-feeling, maybe a mechanical
| window opener based on EspHome for short pulsed passive
| ventilation intervals is actually more efficient, easier to
| implement and need less maintenance? Not aware of any comparisons
| though and last time I checked I could only find some finicky 3d
| printed actors that might not survive a guest opening the window.
| open_erv2 wrote:
| The TW4 is light years ahead. Higher flow, better efficiency,
| much quieter, wind compensation, Internet of things
| functionality. It's not just yet another machine of the same
| kind. The heat exchanger is very different, the whole design
| and construction is quite different.
| snickerer wrote:
| I use similar decentralized (single-room) ventilation units here
| in Northern Germany:
| https://www.bayernluft.de/de/frame.cgi?page=start.
|
| I am super happy with them. We now always have air that feels
| fresh and warm in winter, and the humidity has dropped
| significantly.
|
| There are two types of such ERV devices:
|
| 1. Those with only one air channel that switches directions
| periodically. They use a heat storage element in the airflow.
| OpenERV belongs to this group.
|
| 2. Those with two separate air channels for intake and exhaust at
| the same time. The air does not mix but passes through a heat
| exchanger. Bayernlufter works like this.
|
| The only thing I don't like about Bayernlufter is that it is not
| open source. It is controlled by a Raspberry Pi (or a similar
| clone), and I don't have access to it.
| woolion wrote:
| Is there any reason the source is available as a Google Drive
| link and not on Github (or whatever alternative, Gitlab, etc)?
| Having been burned out by open-source hardware project, checking
| how healthy the git looks is a good indicator.
| open_erv2 wrote:
| The file limit sizes on github are a problem, there is some
| workaround but I haven't gotten around to dealing with it yet.
| dangoodmanUT wrote:
| Try git lfs
| sthoward wrote:
| Try Oxen.ai
| GistNoesis wrote:
| Here OpenERV use a push-pull ventilation design where air
| direction is reversed every 30s. This allows energy recuperation
| and dispense connecting the inlet and the outlet to each other,
| as each ventilation port alternate role simultaneously.
|
| The alternative design is a counter-flow heat exchanger. Using 3d
| printing and gyroids it seems possible to build quite compact
| ones. (metal 3d printed heat exchanger for helicopter
| https://www.youtube.com/watch?v=1qifd3yn9S0 )
|
| 3d-printing a counter-flowing heat-exchanger seems interesting
| but maybe there are some molding issues that need to be taken
| care of (maybe HEPA filters on the inside in/outlet are
| sufficient).
|
| The main advantage of the heat-exchanger solution is that you
| won't need specific electronic control and can reuse the standard
| fans for controlled ventilation, but there is more thermally
| isolated piping required (and the pipes are quite big (~10cm
| diameter) because they need to move a lot of air even if the fans
| are weak).
|
| The push-pull system is harder to DIY because most of the off-the
| shelf fans can't be reversed easily (and 3d printed fans are
| noisy and inefficient).
| open_erv2 wrote:
| Hey guys, I am the guy behind the OpenERV company, who designed
| the TW4 and WM12 ERV units.
|
| I'm sorry I don't have a bunch of units ready to ship out, as the
| site says it's still in beta, I am to be honest kind of taking my
| time because I have another project, the big quiet fan, which is
| actually funded a little better, and thus I've been directing
| most of my time to that. But I do advance this a bit most days. I
| have a twitter where I tweet my progress : @open_erv, and also
| I'm on bluesky.
|
| I have shipped a few units to other engineers who have/will test
| the units so I can share third party confirmation for any
| skeptics.
|
| To clarify some of the discussion, it is not a counterflow heat
| exhanger, it is a regenerative type.
| https://en.wikipedia.org/wiki/Regenerative_heat_exchanger. I
| prefer this type because they can recover latent heat more
| effectively than recouperative (such as counterflow) type, and
| latent heat is 40-50% of the total energy content of the air,
| seasonal average in Ottawa or Toronto.
|
| I am hoping to get the machine tested by the PassiveHaus
| institute to show beyond doubt how good the efficiency is with a
| third party test. I have no doubt, I have tested it myself,
| though.
|
| These can theoretically handy any temperature differential, but
| the TW4 and WM12 are currently made of a polymer that I wouldn't
| trust in an extremely hot climate combined with direct sunlight.
| For that reason, I am focussed on cold climate scenarios. I am
| pretty sure it will not frost up even in extremely cold weather
| like -30. I used it last year in my window and had no problem,
| and it did get to like -25 at least iirc.
| DamonHD wrote:
| Good project. I've added links from my MHRV pages which have
| quite good traction on search.
|
| Small note: the older single-room unit we have with the fan on
| the outside can ice up and make horrible noises then stall at a
| few degrees below zero (here in London UK)... B^>
|
| Also: as the creator of a project called OpenTRV, I cannot but
| help admire your taste in naming! B^> B^>
| open_erv2 wrote:
| That's an amazing project! I'm blessed to be in such company.
| Seriously, I use open source stuff and I prefer to do
| business with such relatively wise people. If you want a beta
| unit, email me and I'll put you at the top of the list!
| DamonHD wrote:
| That's very kind, but I have all the (SR)MHRV units that I
| can reasonably fit!
|
| FWIW the email address on your site page is bouncing for
| me.
|
| Please do add my email (in my profile here) to a low-volume
| mailing/updates list if you have one.
|
| And if my limited experience of bringing an open hardware
| project to market might be of help, let me know!
| gregwebs wrote:
| The ductless design seems great for smaller units or open
| spaces. Although for smaller units you want to get building
| owners to install these. Have you seen interest from them or
| are you expecting a company to take up this design and sell it
| to them?
|
| I would consider installing this in my open finished attic even
| though I already have a whole house ERV. The problem with a
| whole house ERV, particularly in a multi story house is that it
| doesn't necessarily produce a lot of fresh air where you are in
| the house.
| open_erv2 wrote:
| I'm planning to just putter along selling units, making about
| 50% of my living like that, and if a company comes along and
| wants to buy the design/company that's good. If not, I get
| some stuff done, earn a living. This isn't a get rich quick
| scheme, it's an honest living type stuff.
| schneems wrote:
| This is neat! I had some issues with ventilation in a foamed
| house and the only product that's not a whole home ERV (which,
| I didn't have space or ducting) was the Panasonic
| whispercomfort which actually has some requirements that were
| hard to meet (minimum duct length) and the overall efficiency
| isn't that great. We put in two and have fresh air intake on
| our HVAC units. Still we've taken to running at least one
| bathroom or laundry fan non-stop.
|
| I'm excited for more competition in this space. Beyond the
| hardware I've found that HVAC installers are way behind the
| curve on air quality. I hope education and awareness increases
| in the industry.
| benj111 wrote:
| >To clarify some of the discussion, it is not a counterflow
| heat exchanger, it is a regenerative type.
|
| Can someone expand of this?
|
| intuition tells me that a regenerative design can be no better
| than 50% efficient, and would be worse at recovering latent
| heat
| ljosa wrote:
| I think it means that it's like
| [Lunos](https://www.lunos.de/en/for-heat-recovery). The unit
| alternates between exhaust and intake every couple of
| minutes. The air being exhausted heats up a core, which in
| the next cycle warms the air from the outside. Lunos e2 is
| advertised to recover 90% of heat and 20-30% of humidity.
| benj111 wrote:
| yes i get that, but say you have an indoor temp of 30c and
| an outdoor temp of 0c. the average of this heat exchanger
| is going to be 15c. so on average youre only cooling the
| exhaust down to 15, and heating up the intake to 15c.
|
| a counter flow heat exchanger can get the temperature
| higher than the average because 30c exhaust is meeting
| partially warmed intake, and 0c intake is meeting partially
| cooled exhaust.
|
| Unless theres a phase change???
| bittercynic wrote:
| Though the average temp of the overall core may be 15c,
| there may be a thermal gradient along the length, so
| maybe the inside end averages 28c and the outside end
| averages 2c, or something like that.
| nabakin wrote:
| Fyi the mobile image swipe mechanic on the linked page is
| inverted. Swiping left takes you to the image on the left,
| instead of the image on the right and vice versa.
| Abekkus wrote:
| Is there a link to the big quiet fan project?
| vizzah wrote:
| I was just recently researching these units..
|
| This model is available in Europe for about 900 EUR:
| https://www.international.zehnder-systems.com/en/comfortable...
| tantalor wrote:
| > Fresh outdoor air
|
| But this is actually treating _indoor_ air, that 's very
| confusing.
|
| Fresh outdoor air is easy to find: just go outside!
| brodouevencode wrote:
| You're also only going to get clean outdoor air in rural places
| where there is no/minimal farming and construction.
| wakeforce wrote:
| I'd love to build this. I have access to a 3d printer, use
| Python, and have some electronics experience. I live in a
| northern climate and have been eyeing ERV systems for a while.
| Basically, I'm the perfect target for this.
|
| However, reading the docs, they seem written more to discourage
| any kind of DIY attempt by saying things A, B or C are difficult,
| than actually explaining how to do them correctly. I'd love to
| contribute to the project, but it feels like it's not set-up to
| foster community contribution.
|
| If I'm mistaken, I'd love to donate some of my time on this!
| Aurornis wrote:
| I expected a community open source project from the title, but
| reading the docs led me to the same conclusion: The website is
| about convincing you to buy one while discouraging you from
| attempting to build one.
|
| It looks like a fun project. I don't want to discount what has
| been designed and built. It is confusing to start reading about
| the project and discover that it's more of a business than a
| community project while simultaneously being unavailable for
| purchase. The person who built it commented on HN that they're
| focused on a 3rd different fan project right now, which brings
| the future of this project into question.
|
| It would be great if a community effort could fork this project
| and work on making it easier to DIY so the community could push
| it forward.
|
| EDIT: After exploring the files I'm not sure I'd even call this
| open source. I either can't find some key files or they're
| deliberately excluded. True open source projects would also
| include the CAD source, not only .STLs so others could adapt
| and modify the source. I think the open angle on this project
| is more marketing than substance.
| open_erv2 wrote:
| The step files are also there, which is the best common
| denominator for CAD files. Again, it's open source for the
| purpose of maintenance and repair, not cloning, and frankly
| earlier on I did make it more community oriented and _nobody_
| ever contributed even a little bit, so I just gave up on that
| idea.
|
| The most likely scenario for longer term is that people may
| submit minor patches or suggestions, which I roll into the
| hardware or firmware. In reality, hardware is not like
| software. You can't make changes easily. Some wizards may
| take it upon themselves to spruce up the firmware with fancy
| features and release something, which anyone is free to do.
| There would then be multiple compatible versions of the
| firmware, one which I curate for reliability with minimal
| features, and others which others can provide. Same as for 3d
| printer firmware. The firmware is
| Micropython, which is extremely easy to understand and
| modify.
| zajio1am wrote:
| It is _not_ open source (per OSI definition), as it is under
| CC BY-NC-SA.
| turtlebits wrote:
| Unfortunately the recovery core, which is the interesting part
| of an ERV, is not included in the 3d stl's.
|
| IMO, this feels like a more marketing project than anything
| open. ERVs are already very simple (a recovery core +
| blowers/fans). Commercial units last an extremely long time
| (some with 10 year warranties) and have comprehensive parts
| availability.
|
| Also a long term window install is a bit janky and is likely to
| lose out on efficiency due to glass being a poor insulator.
| NavinF wrote:
| I'm pretty sure stls/regen.stl is the recovery core you're
| taking about tho I can't open it in a online stl viewer: http
| s://drive.google.com/drive/folders/1py2YwmwBEcvmdw18SKwx...
|
| In the photos it seems to be a bunch of nested single-
| perimeter cylinders that are joined at a few points to
| maintain spacing. Easy enough to model, but I agree the
| documentation is horrible and there's no way to contribute.
|
| Commercial units are not comparable because they're way more
| expensive despite being so simple
| bittercynic wrote:
| Prusaslicer opens it, and it is the right size and shape to
| be the core, but there's no internal geometry in that STL,
| at least not how Prusaslicer renders it.
|
| I'd be interested in seeing a diagram of how the air flows
| through it, if such a thing is available.
|
| Edited to add: There are instructions in the WM12 manual to
| use your infill settings to make the old version of the
| core. Page 15 of the manual states there is a python script
| in the source files to generate the new core, but it only
| works for their particular printer. I wasn't able to find
| the script.
| schneems wrote:
| Thanks for mentioning that. It seems the PDF and the
| google docs "manual" have diverged a bit. (at least in
| page numbers).
|
| I was curious about materials for the core. I know that
| they're supposed to exchange humidity as well as heat. I
| know PLA will absorb and release water but I would guess
| it wouldn't transfer enough to be very efficient. Though
| I would be happy to be wrong.
|
| I assume the Core in my Panasonic whisper comfort was
| made out of something more permeable than "simply"
| extruded plastic. (would love to know more if someone has
| details).
| turtlebits wrote:
| You can get a commercial unit for under $400 USD. Search
| for "Pioneer 50 ERV", which claims 97% efficiency or look
| on aliexpress for units under $200.
|
| That said, I find these "regenerative" heat exchangers too
| limiting as they generally only work for a single
| room/space.
| open_erv2 wrote:
| There is the tw4, which is made to be put in a wall, and
| there is the WM12, which goes in the window. The main focus
| is the TW4. There are instructions in the manual for making
| an ERV core. It is not trivial.
| NavinF wrote:
| Interesting. I'll paste it below.
|
| Note on printing the regenerator/heat exchanger:
|
| The latest and greatest heat exchanger is produced directly
| with python script generated gcode specific to the printer
| I use and cannot be practically produced diy,
| unfortunately. However the old model can be, and the STL is
| included for that, in the source repository. To do this,
| simply use Cura, load th STL in, put it in the center of
| the build plate, and set it to do "lines" infill with about
| 2.5 mm on center (between centers of the lines) spacing and
| 0.45 mm width, no top layer and no bottom layer (set them
| to zero). Check the preview and it should show you a
| structure which is much like grid infill, parallel channels
| which are square in cross section, with the outer wall.
| Tape can be applied over the nubs on the side to fit in an
| oversized pipe, or they can be sanded if the pipe is too
| small. You could also use grid infill, but the roads tend
| to have problems where they intersect. When the nozzle goes
| over one road, it wipes the plastic off, and not enough is
| deposited on the lee side. I don't know how to solve this
| in Cura without using lines infill. If you could make it so
| the nozzle went in alternate directions each layer that
| would probably solve it well enough.
| fudged71 wrote:
| I understand that the addition of desiccant material is the
| core aspect of what makes this an ERV. I don't actually see
| any clear explanation of how the desiccant material is
| added to the printed part. While the creator (open_erv2)
| mentions that sorbent/desiccant can be used to handle
| moisture ("If you have sorbent, it gets grabbed out of the
| air before it can condense"), they don't specify how it's
| incorporated into the design.
|
| Is it added mid-print? After printing? Is it difficult to
| add?
| outlog wrote:
| just saw this video https://www.youtube.com/watch?v=U-hVUczzlL4
| and you get a very smart solution for a fair price, that does
| coordination etc.. and it's even esp32 based should the need
| arise. see https://www.bpcventilation.com/bsk-zephyr-single-
| room-heat-r...
|
| I also have this DIY bookmarked:
| https://www.youtube.com/watch?v=wJB3dyHDa-8
| aojdwhsd wrote:
| This looks great. How well does the WM12 circulate the air, with
| the intake and exhaust being so close?
| ucefkh wrote:
| This is amazing but needs much clearer docs rbh
| NavinF wrote:
| Could you post a higher quality photo of the heat exchanger? Is
| it 3d printed plastic?
|
| How did you get the fans to run backwards? They look like
| standard PC fans
| funsi wrote:
| I am looking at buying one of these and have had a look at
| similar (but not open-source) products available on Alibaba, e.g.
| https://www.alibaba.com/product-detail/Fresh-Air-Ventilation...
|
| Prices there start at $150 + shipping.
|
| Has anyone tested these?
| coryfklein wrote:
| Wait, is the air outdoors generally cleaner than the air indoors?
| Certainly not true in the Salt Lake valley for the 4 months of
| the year we get persistent inversion.
| NavinF wrote:
| The CO2 levels outside are definitely lower than inside. Often
| by 4x. Fixing that without freezing is the main use case for an
| ERV
| farawayea wrote:
| Some of these instructions have fiber glass or similar for
| insulation which appears to be used for this. It's not something
| anyone would want next to their ventilation system or inside it.
|
| This isn't something to even consider without some expert
| reviews. The projects are also work in progress and overall
| incomplete with many details missing.
|
| Be careful when you do anything involving ERV and HRV. It's very
| easy to cause serious damage to the property you live in, harm
| yourself and others in an irreversible way, or even both.
| elric wrote:
| I installed a central ERV in my home, a Zehnder ComfoAir Q.
| Installing it was quite involved, but not hard. Definitely within
| reach of anyone with basic DIY skills.
|
| The hardest part is finding a good spot for the ventilation unit,
| which is about the size of a large, old CRT TV. You have to run
| ducting from there to multiple rooms, but their ducting system is
| easy to install.
|
| Mine draws about 20W/hour at its typical setting, and it greatly
| improves comfort. Keeps some of the humidity out when it's humid
| out, keeps some moisture in when it's dry out. Fresh air year
| round. Keeps mosquitos out. Keeps some dust/particulates out.
|
| Worth the effort, even in my small house.
|
| A decentralized unit would be a lot easier to install, but I
| imagine it's less efficient, less suitable for larger dwellings,
| and probably louder. YMMV.
| xnx wrote:
| This guy on YouTube built a very clever DIY HRV, but got rid of
| it and went with a commercial ERV:
| https://www.youtube.com/watch?v=LiptsaKmq80
| fudged71 wrote:
| What happens if power fails or one unit stops working? Without
| valves, you could get unwanted air exchange through a non-
| operating unit. The commenters discuss various aspects of the
| design in detail, but surprisingly no one brings up this
| potential failure mode.
| UniverseHacker wrote:
| This is really cool! I try to keep CO2 at reasonable levels at
| home, and that occasionally results in running the heater with
| the windows open. My friends/family do not understand why I care
| or would waste energy like that, and seem to think it is a mental
| illness or something.
|
| The worst scenario is during high wildfire smoke events... trying
| to keep the house sealed enough to keep the smoke out often
| requires taping door seams, etc. and the CO2 skyrockets.
| jtbayly wrote:
| I'm interested in this, but I think I just realized that what I
| want it to do is impossible.
|
| We have a fireplace, which is not efficient at all, in part
| because it sucks cold air in from the outside. I was thinking it
| would be great it we could use an ERV to condition the air that
| gets brought in.
|
| However, as far as I can tell, the moment you exhaust air from
| your house in any way except through the ERV itself, the ERV
| cannot help you with the replacement air that comes in.
|
| Is that correct?
| tempestn wrote:
| It would be cool if someone could build a chimney ERV: extract
| heat from the dirty air produced by fire, and inject it into
| fresh air pulled into the living space. So I guess basically it
| would function like a regular ERV, but with a fire in the
| exhaust path. (Probably not feasible with a wood fire, but
| maybe with gas?)
| tempestn wrote:
| Maybe this thing works that way?
| https://www.modlar.com/brands/nu-air-ventilation-systems-
| inc...
| turtlebits wrote:
| If you can use the exhaust heat to temper the incoming outside
| air, that's all an ERV does. Or, get a direct vent fireplace
| (draws in outdoor air)
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