I've been trying to fully understand HRVs ERVs for months and although I got to where I understood what they did, I had no idea of how they did it. Of the dozens of videos I've watched, your video is the ONLY one I've found that gave me the information I wanted. Excellent job!!
Thank you. If you want to dive deeper, we did a 1.5 hour webinar on this same topic today. You can watch it at attendee.gotowebinar.com/register/3857937118863671564
@@TECTubefilms Awesome! I'll definitely check it out, but it will be 2 or 3 days from now. Unless I flake out on my responsibilities, then it will be sooner, so it'll probably be sooner...
This video as really good at explaining ERVs. My HVACR class stumbled across you video of the psychrometric chart and it was very informative. I have copied this link and shared it with my instructor because I feel like our class will benefit from this training as well. Thank you for your videos and I look forward to viewing more of your content as needed.
Thank you for the video. I never came across ERVs in my 8 year long career as a facilities maintenance manager. I came across this technology when I moved to a cold country last year and really wanted to know how they worked.
I always assumed HRVs are a waste of money. But I live in Monterey Ca where the climate is mild and perfect. But this video explained it great. I can now see them being beneficial in extreme temps with extreme humidity where fresh air is important.
This is the best demonstration I have seen to explain the ERV function. I was surprised at how well the ERV was able to transfer temperature in the demo. I wonder if you could generate some steam at the outside air input and also see how well the humidity would be transferred using RH gauges in each chamber as well as thermometers. Also, it would be interesting to compare the efficiency difference from the rotating membrane compared to the usual home module.
There is plenty of data to illustrate the efficiency different between an enthalpy wheel and fixed plates. Put wheels are only for commercial projects. No one makes a wheel small enough for residential.
Look, I just stumbled across this video. I'm a network engineer and understood 0% of how A/C, ventilation, HVAC, etc worked. But this guy did a GREAT job explaining this! (*me yelling across the house* "Hey honey, you want me to explain to you how an ERV keeps a building cool?!") That's right, I'm that kind of nerd who MUST share facts about things i'm excited to learn. 😋🤣
Yea this guys explination is top notch! I couldnt make heads or tails of why this type of system is used or its purpose... Now I want 1! lmao Oh and dont worry the nerds will inherit the earth! :P
Awesome video! ASHRAE recommends as much as outside air as possible for COVID. This is great technology to have to allow taking mostly outside air even when it’s hot or cold outside without impacting energy usage or performance.
Blown away by how effective it works in that final demo. I'd expect to split the difference 50/50 on temperature at best, but it seems you're closer to 90% thermal energy rejection which is nuts.
For commercial systems, the minimum per most energy codes is 50% total recovery (sensible + latent). Most wheels are 65 to 75%, but some can be higher.
Yes, per give area of space, a wheel generally trumps all other ERV types. For example, one of the manufacturers we use can run 30,000 CFM thru a wheel in a certain size cabinet. However, when they use that same exact cabinet chassis for a fixed plate ERV, they can only do a our 12,000 thru it.
This is an absolutely excellent video explanation. Close-ups, hands on, shows what's happening. He mentioned an exhaust duct "from FURNACE to HRV, then vented outside" at 5:55. Is this true, or was this duct pulling exhaust from bathroom? I'm trying to understand how to tie into existing HVAC ducting.
Yes, in this particular ducting scenario (and there is more than one way to duct it), the HRV pulls air from the furnace return and exhausts it outside. It then pulls air from the outside and replaces it in that return duct. This is the easiest way to duct it, but it also doesn't save any energy. The best way... as you hinted at... would be to pull air from the bathroom instead of using a bath fan and run that thru the HRV instead of pulling return air. This is air you planned to throw away anyway so may as well reclaim energy from it.
@@TECTubefilms Ok interesting. Thank you. I'm less worried about energy, more worried about excessive redundant systems, ducting, and wall penetrations (bath fans, HRV, kitchen fans, makeup air, furnace, dryer ducts, etc). Do they make enthalpy core boxes (without the HRV blowers) that can duct straight to the air handler using its central fan? To consolidate some of these duplications? Which vents can be combined? I don't understand why we ditch the high CFM flow rates and high MERV filtration of an air handler for these tasks, and instead use these dinky little 100cfm central exchangers. In full redundancy no less.
@@slipperyslope3912 Pretty much the ONLY reason to install a HRV is to save energy. If you don't need/want the energy savings and just want fresh air, then there are several methods to duct outside air into the HVAC system without the expense of a HRV.
@@slipperyslope3912 No, we have never seen a residential size HRV without a fan. Just ducting it into the air handler would not work. The pressure drop of the HRV heat exchanger and filters is so high, that the air handler will just draw all of its air from the return duct and none from the HRV duct.
@@slipperyslope3912 You do not lose the MERV filtration with a HRV ducted into an air handler. The outside air coming thru the HRV is ducted into the return of the air handler upstream of the air handler's filter.
I'm thinking of building an small HRV, is there an advantage to the wheel type vs fixed fins? Leaning towards fixed fins and doing multiple cross flow cores or a single counter flow as it would be easier to build, but the wheel ones are also kinda intriguing.
The advantage of a wheel is that it has significantly higher heat transfer ability for a given size of cabinet. The disadvantage of a wheel is if you need AHRI certification for zero crossover (aka EATR).
You described a dedicated HRV system for residential use. Typically these will be ducted to all the bathrooms as well as the kitchen (with a grease filter in place). Never a hallway like you said That being said, most residential HRVs will not be installed like this. You will just have your supply and return for your HRV tied into the return duct (3' apart) and an intake and exhaust going outside (6' apart)
We agree to pull air from the bathrooms as the first choice. If you need to pull more exhaust air (to balance with your required ventilation intake air) we would prefer to pull it from the kitchen (but not the hood) or from a general area like a hallway. We do not recommend pulling air from the kitchen hood since grease filters do not capture all of the grease, nor do homeowners change/clean them regularly.
We are not fans of pulling the air out of the furnace return duct to send thru the ERV and then outside. This is an energy waster. To make it an energy conservation device, you must recovery the energy from a waste stream... air that was leaving the house anyway even if you did not own an ERV.
I'm surprised the wheel spins that fast. I thought that each section of the wheel would need much more time to absorb the heat and change temperature before being able to transfer the heat to the other side. What material is the wheel and how is it able to transfer heat while spinning so fast?
We would consider this to be pretty slow. ERV wheels rotate at 10 to 60 RPM (similar to an old school record player), whereas a fan is rotating at 1,800 to 3,600 RPM.
In summer, hot moisture air is sucked from outside, and this hot energy is transferred to heat exchanger, there by the hot air losing it's energy to heat exchanger and converts to cold air which is then pushed inside the building space...and vice versa in winter...is it right?..pls confirm.
In the UK we have humid winters, where ventilation is key to keeping the inside of homes warm and dry. Many people are talking about positive input ventilation (opposite of extractor fan just pumping fresh air into a central place to be blown through gaps of the building).. This increases heating cost as many units have a 500w duct heater to warm up the incoming air stream (~10c to -2c typically) and even then people complain of cold drafts from the unit.. I wonder if an HRV would help benefit. Use the damp but warm exhaust from bathroom to preheat the incoming air somewhat..
Yes, you can run the bathroom exhaust through an HRV to reclaim the heat and transfer it to the incoming ventilation air to pre-heat that air less expensively.
In a residential ERV with the set of separator "fins" (at 6:15), my main point of confusion is why, after passing through the box, the temperature of the air entering the building isn't the same as the air going out of the building (the average temperature). I'd think the fins would take the average temperature of the air passing into the unit, and so exhaust air would be moderated and not so efficiently exchanged as it seems to be. If we looked at a single fin (as a square), would we see a large heat difference across the surface of that fin? Is that how we're able to recover such a large amount of heat via the device?
The incoming air is not heated/cooled to the same temp as the outgoing air because the heat exchange process is imperfect. Depending on the model and type of heat exchanger, it can usually recover 55 to 85% of the available energy, but not all of it.
@@TECTubefilms Basically, the device is more efficient than I expected was possible from such a simple device. If the temperature was 20F outside and 70F inside, my prior guess was that the device would yield fresh air to the inside closer to the average of the two temperatures at 45F (with exhaust air at a similar temperature). Given that the heat recovery is in reality far more efficient than this, my assumption/guess is that the temperature is very different along different parts on each "fin" on the heat exchanger. (I'm not sure I can properly explain what I'm saying in a comment, as I'm discussing a 3D object in text only.)
@@dosadoodle If the temperature was only average of the two air streams, that would mean that it is a 50% effective heat transfer device. As mentioned, most are 55 to 85%. For commercial buildings, the minimum allowed per energy code (IECC) is 50% effective. There is no minimum for residential. The reason any heat exchange coil can be better than 50% is due to counterflow arrangement. If you want to dive deep into the technology on how ERV heat transfer works, you may want to check out one of our recorded webinars such as attendee.gotowebinar.com/register/6256885680768066575
There is a query I'll be grateful to get looked upon by experts like you. I was concerned that the temperature difference of the Air Streams going in and out (in case of an HRV) that could condense the water content in the humid air. Won't this happen and the condensed water will drip from the duct pipes?
Condensation can occur if one airstream's temp is below the dewpoint of the other airstream. Many HRVs have a condensation pan and drain line for this reason. The ductwork between the HRV and the furnace should not condense, though. In order for that to happen, the duct temp would need to get below the dewpoint of the air in the room that contains the ducts. That will be difficult to do without refrigeration. Sometimes, however, this will occur on the ductwork between the HRV and the outdoors. Although that will happen on ductwork to the outdoors even if you do not have an HRV. The two ducts going to the outside should be insulated ducts like we showed on the HRV in the second half of this video.
@@UPsideDOWNworld321 Are you saying you have a swamp cooler instead of an air conditioner (FYI - swamp cooler is slang for a type of cooling system used in desert climates). An ERV isn't going to help in that case. And ERV recovers heat/cool energy from your exhaust air and transfers it to your incoming ventilation air. Nothing more.
No molecules of the air are separated. The air molecules pass straight through the wheel. In regards to the heat... heat always moves from hot thing to cold thing, so if the air is warmer than the wheel, then the air heats the wheel. Then the wheel spins to the other airstream where the wheel is not the warm thing so it transfers its heat to that cooler airstream.
useful in the age of COVID when we want more fresh outside air coming in, and human exhalation going out of the building, without too much loss of heat or cooling
Great/fantastic/excellent video, love the plexiglass. I am looking for a similar system, but where the air exchanger could be bypass in spring & fall (hot days & cool night & since air is so cool at night, there would be no need to have the AC on). Am I missing something here? I can’t seem to find a system that does that.
Yes, most commercial ERVs have a bypass around the heat exchanger for "economizer days," since this is required now by IECC and most other energy codes.
Is there a measurement of how much energy is "lost" in this process? I realize that something can be derived based on that demo with the thermometers I am just curious if there have been papers/studies published on these.
Yes, but what do you mean by "lost?" Are you trying to figure out how much fan energy is being used to move this air? If that is the case, most selection software tools will tell you this kWh. Or are you trying to figure out how much heat is not being transferred that could be? If this is the case, then that is represented in the AHRI rated "effectiveness" percentage. Or are your trying to figure out how much leakage goes around the wheel on accident? This is represented by AHRI's measurements of OACF and EATR.
Well... a HRV is not right for every application. It only saves energy if you already have a stream of exhaust air to recover from. And it only "pays back" if you have a lot of required outside air and the building is in an area with high utility costs. Where we are in northern Illinois, it starts making a lot of financial sense when the HVAC system requires more 1,000 CFM of outside air intake. If your building is in a state with more expensive energy costs, smaller HRVs can make sense too.
An ERV is a way to save the energy cost of ventilation air. It doesn't clean or purifier the air. It provides the same dilution affect that other ventilation system would also provide... it just does it with less heating/cooling energy.
If you are interested in viral transmission reduction in commercial buildings, check out our webinar on IAQ. register.gotowebinar.com/register/5473581496208425740
@@TECTubefilms I fully understand the function. My comment stands. I did not suggest that it cleans or purifies the air. Indeed, there is no way an HVAC system can filter viruses out of air transmitted directly from person to person in close proximity, even if filters could be so fine. My point is that in enclosed spaces with multiple occupants, the direction of airflow, its replacement frequency and dilution with fresh air are critical factors in reducing the concentration of pathogens in each breath of air we inhale. I was suggesting that individual occupants should have maximum supply of outside air to breathe - as opposed to air exhaled from others' lungs. This would seem to be accomplished by arranging airflow from floor to ceiling with fresh air constantly supplied with minimal turbulence. Energy recovery is required to make such a design economically practical beyond capital cost considerations.
@@TheCablebill BTW - we do have a filtration system that filters viruses out of the air in an occupied space. We have been using these in hospitals for about 8 years. If you are interested in learning more, check out attendee.gotowebinar.com/register/2854708624619222797
I have a question for you I just started working at a three story hotel I happen to go in the attic and found an ERV not running and hasn't been in awhile we have ducted energy on the first floor and Ptac units in all the rooms would it be wise to get the ERV running again to save energy cost or not ?
It depends on the classification of the air in the exhaust and the specific local mechanical code. For example, if it is general exhaust and you are under IMC, then usually 10% can be recirculated from exhaust back into supply... or what AHRI calls Exhaust Air Transfer Ration (EATR). Other classes of air can be 5% or 0% in IMC.
What should the house exterior intake cover look like? We have a 8"x 8" bug screen with louvred flaps, but someone pointed out that it should be a boot cover, so that the outside air coming in is not impeded by the closed louvre flaps. Does it matter? Thank you, great video!
We have a huge one in our building's air handling unit. We are seeing only about 8-10 degree drop from supply air temp before it hits our chilled water coil. In our area, our summers can be quite hot (100+) and seeing your demonstration, I am wondering if our wheel is not doing what it's supposed to! hmmm
Lots of possible issues: wheel could be dirty, you may not have enough exhaust CFM relative to supply CFM, your exhaust air may be too warm, wheel could be moving the wrong speed
@@TECTubefilms Ok. I have noticed that our exhaust CFM, when raised, the evap cooler does lower the supply, however, it creates negative pressure in our building. I will have to check the wheel's RPM as it was recently installed after our original wheel feel apart. Thanks for the feedback!
@@FloresEsteban1979 Wow! Your wheel fell apart? We have never heard of anything like that. Who was the original wheel manufacturer? Did you replace it with a different brand of wheel?
@@FloresEsteban1979 What is the exhaust air CFM and the outside air supply CFM? Are there other sources of exhaust in the building? If you want the space balanced instead of negative... and most buildings do... you need to move all of the building's exhaust air through the ERV and not use other exhaust fans.
@@TECTubefilms Yes, it was designed to have some positive pressure. The normal CFM during a regular business day is around 800-900 Exhaust and 7000 Supply at the air handler.
You "could" but a residential size HRV in an office building, but it would not be large enough. The HRV should be sized based on the exhaust and outside CFM flows that the building was designed for. Residential ERVs are generally under 300 CFM, which would be very small for a regular office building. Unless you are talking about a small business office with just 10 people.
Im thinking put stale intake for ERV in bathroom and above range. Could the fans be done away with? How many CFM per square ft? I saw another video it had U.S. divided into HRV or ERV. I live in ERV area but about 40 miles to HRV suggested area. Would it be beneficial to get a HRV
Yes, you can run bathroom air thru an ERV. We would not recommend you run air from the range. It has grease that you do not want to get on the ERV's heat exchanger. So use exhaust air from bathrooms and maybe a general area of the kitchen or a hallway. In this case you would completely eliminate the bath fans and just have a grill in the bathroom ceilings that duct to the ERV. Then have the ERV supply fresh air to the bedrooms and living room or have it bring the fresh air to the return duct for the furnace or main air handler.
From homes an ERV is almost always better than a HRV because it recovers moisture, as well. This keep moisture out in the summer and keeps it in during the winter. The reason there are maps to show not using ERVs in northern climates is because the ERV can develop frost on it from that moisture. Larger commercial ERVs have controls and/or heaters to avoid that, but that is not cost effective for small residential ERVs. So as you get to colder climates, you need to use a HRV for homes. The border for HRV vs ERV is specific to each manufacturer and their heat exchanger technology. So you need to look at the map specific to the model of ERV you are considering.
Not sure how to answer your question about installing one yourself. You would need knowledge of HVAC design/sizing, sheetmetal working, and electrical wiring, and in some states/municipalities licenses to do work in those trades. Plus the smallest enthalpy wheels on the market are too large for homes. Residential applications would us the enthalpy core style.
Hello, I have a barndominium home that has spray foam insulation. The SPF is not allowing any fresh air into the home and it off gasses some during the summertime. My goal is to bring in fresh air to help with the off gassing. Which of the 2 devices would help me better, an ERV or whole house ventilator with dehumidifier? Also, does the ERV only work when the HVAC system is running? Thank you for your time.
The ERV will be less expensive to operate. The dehumidifier can remove moisture from both the indoor air and the incoming outside air. The ERV will only remove moisture from the incoming outside air.
I love the ERV demo unit, makes it simple to see during the summer months how the temp exchange works. I wonder if you have made a video with this reversed, showing the intake/exhaust during winter month where cold air is being introduced to the inside? I recently built an air tight house and do not have any type of ventilation system installed, hence it's drawing from the windows and doors creating a vapor in the cracks. I also have humidity levels that are running between 60-70% showing on my thermostat, btw I live in Alabama. I'm thinking I need an ERV to help bring in fresh air to balance things. Will this also help to lower my humidity level?
No, we did not make a winter video. However, it would do the same thing as the demo in this video. Just move the labels around. Instead of the warm air being labelled as "outside air," it would be "return air."
An ERV will only help with indoor humidity issues if the humidity is being caused by outside air coming in. When the ERV brings in the outside air in the summer, it transfers the heat and the moisture to the exiting exhaust air so it does not come back in. However, if the source of your high humidity is something inside the house, then an ERV will make the problem worse since it will transfer the humidity from the return air back into the supply air. So the first question with any humidity issue is "what is the source of the moisture?"
There are lots of things you can do to deal with high indoor humidity. This would be an abbreviated list from best to worst (the list changes though based on WHY you have high humidity). 1) eliminate moisture sources (put caps on sump and ejector pits, run bath fan when showering, etc) 2) Right-size the A/C. 99% of all system are oversized and more than half are grossly oversized. The smaller the A/C capacity, the longer the run cycle, and hence the better the dehumidification 3) Multi-stage A/C. This also keeps the system running and the evaporator dehumidifying 4) Lower blower speed for regular A/C mode 5) On demand dehumidification using the A/C and lowering the blower speed even lower than regular A/C mode 6) On demand dehumidification using the A/C but not lowering blower speed further because the system is too basic to do that 7) Slightly larger evaporator coil with more surface area 8) dehumidifier You should note that some of the decisions above affect other stuff so should not be modified without research. For example, you may lower blower speed to dehumidify better but then realize you have a crappy duct system and can no longer get enough air to certain rooms.
Great video! What happens if its warm inside the house and you want to have the cold air outside to cool your house. That is the scenario in tropical countries where at night time it is usually colder outside than inside. Can I still pump in fresh air at the same time make inside the house cooler?
That scenario occurs frequently in commercial buildings so the units include an automated bypass which allows air to run thru the ERV fans and duct without going thru the actual heat exchanger. This is in place of the economizer that most standard commercial HVAC air handlers have. Small residential ERVs do not typically have a bypass, just like residential HVAC systems do not have economizers systems. The first cost is too high in residential for the energy cost benefit.
a mixing box would be perfect for residential applications. It brings in cooler dryer air from the outside and lowers the energy load on your cooling system .
In a core-style residential unit like you showed, is it possible to turn an ERV into an HRV (or vice versa) simply by changing the core from one with a metal heat exchanger to a polymer heat exchanger (or vice versa)?
If the ERV is ducted into the main HVAC system, then they should be on/off together. Keep in mind that ventilation in a commercial building is required constantly, hence both the ERV and HVAC need to be on, during the buildings occupied hours.
@TECTubefilms thanks for the reply that's what I thought was the case for my ducted system for my residence. The builder told everyone in my neighborhood that it needs to be on 24/7 and taped the switch on. We are not in a high humidity zone (cen California).
@@hctibeyb1788 The climate won't affect the code requirement to run the system 24/7 or not. Modern residential, like commercial for a long time, requires continuous ventilation.
If not too complex for your controls scheme, we would suggest running it when the home is occupied. Many smart thermostats can handle that. Or if not, you can at least tie the ERV to run off the EAC terminals of the furnace so it is engaged when the main fan is engaged... and then program your fan to run constant during occupied hours and intermittent during unoccupied.
Where do I get the wheel? Can I make my own wheel? And how well does the seal between the spinning wheel have to be? Do you have a miniature version of this system for a small 2 bedroom house?
The wheel in this video is the miniature version. Wheels are only used in commercial ERVs which range from about 500 to 50,000 CFM. Some of these are 10 ft in diameter. However, if you really want, Airxchange does make one down to just 50 CFM, but it would be very cost prohibitive to build a residential sized version with that wheel. For those small sizes, it would be less expensive and more reliable to use a "packaged" residential ERV which normally has an enthalpy core instead of a wheel and motor.
You do not need to seal between the wheel and the cabinet... in fact you really cannot because the wheel is in motion. However, by properly positing the two fans for pressure control, you can insure minimal to zero leakage for EATR and OACF. You may want to check out this webinar if you want to learn more about ERVs and wheels - attendee.gotowebinar.com/register/3857937118863671564
An ERV only saves the energy associated with conditioning your ventilation air. It has no relation to the cooling energy which is represented by the SEER rating.
@@TECTubefilms so it makes conitioned or heated ventliated air stay cooling or warmer longer so I stay comfortable longer and ac doesnt have to kick on so often ?
@@joeydelmarsjr.646 We suppose you could think of it like that. It makes the ventilation air from outside cooler as it comes into the house during the summer (and warmer in the winter) for nearly no energy cost. Hence this would allow your A/C to not run as much if that is what you were previously using to cool your outside air. It will also dehumidify (summer) or humidify (winter) that incoming outside air and that will certainly improve occupant comfort.
If I wanted a system to reduce building/room air humidity as much as possible for a specific production purpose but keep the heat in, which one would I want?
If the moisture is being introduced by outside air coming into the building via the ventilation system, then you would want an ERV. If the moisture is due to indoor sources (pool, people, fountains, etc) then you would want a HRV.
razz P It basically recovers heat from the indoor air as it replaces the indoor air with the outdoor air. It's just an indoor quality improvement device. Keeps indoor air fresh without the added cost of cooling it or heating it, depending on the season. Hope that helps.
Guess it be a hard question to answer. But curious how many celsius is the coming in air heated by? Guess the ultimate savings would be to not use the HVR/EVR, and just recirculate stale air. :). I assume HVR only need to be on while people are in home?
ERVs save energy if you have a stream of exhaust air to recover energy from. So if you already have sources of exhaust air (such as bathrooms, pressurization control fans, etc), instead of throwing that conditioned air away, you can first save its energy. The amount of energy savings... and more importantly, the amount of dollars saved, depend on the specifics of the project and the utility costs.
The commercial ERV in the video is from MicorMetl and uses an Airxchange wheel. The residential fixed plate ERV is from Lifebreath. The clear demo module uses and Airchange wheel also.
i’m replacing the capacitor on the fan, after the erv has been inactive for a couple years. there is some corrosion too. the fan spins, but it is like a bike wheel where there is contact with a brake pad, rather than a smooth spin that keeps going after released. how easily should the fan spin?
It might be a "sweeper" that is slowing it down. That is a little brush like you have under your exterior doors. It is there to reduce inadvertent transfer. But in any case, you need to figure out what is slowing the wheel down when you spin it by hand and then decide if that is supposed to be there or not.
Silica beads are used as desiccant in thermal pane windows, but they eventually become saturated. Doesn't the silica-gel wheel eventually become saturated? I know it will vary with a number of factors but how often might one have to be changed? Annually? Bi-annually? Every two years?
No, they do not become saturated. They are "dried" as the wheel cycles into the other airstream which has a lower moisture content. In this application they only temporarily absorb water vapor for the purpose of transferring it to be released seconds later.
Neither the wheel, nor the silica gel impregnated into it, need to be changed at all. The life span is over 20 years, which will outlive the sheetmetal air handler that it is typically mounted in.
How can the enthalpy core possibly transfer moisture from one stream to the other without transferring bacteria and toxins with it? Moisture is water? I can understand the core transferring heat without mixing airstreams but moisture. I am just not sure how that works.
We suppose the simple answer is that the enthalpy core wicks the moisture through the media. This allows it to move moisture but not air. If there was something in the moisture... and that something was smaller that a grain of moisture, we suppose that something would also get pulled through. The IMC allows either 5 or 10% leakage of air from the exhaust to the supply depending on the category of exhaust air used in the ERV. What you are describing would be tenths of a percent, so it would be of no concern. Plus if you think about it, the supply air is going back into the same room(s) that the exhaust air came from in most applications.
What is the material of the fan in the demo unit? Is it a metal sheet? And when we turn it on, the motor on both ends are the one pulling the air making the middle turbine moves by itself? (Wanting to make one for the house) please help :)
No, it is not metal. The heat transfer wheel is a polymer impregnated with silica gel desiccant to allow moisture transfer, as well as heat. This type of ERV is not cost effective for small systems less than about 1,500 CFM. Residential only needs 60 to 120 CFM of outside air so in those applications we use entahlpy cores for heat transfer instead.
The two fans are to move air in and out of a building... you are exchanging heat and moisture between them. They do not make the heat transfer wheel (what you called a turbine) move. That is moved with a fractional hp motor and a polymer belt.
ERVs do not cool buildings, nor do they dehumidify them. The only thing they can do to help with heating and cooling is use your exhaust air to pre-cool and pre-dehumidify your ventilation air coming. The amount of ventilation air you need to bring in... and hence how large of an ERV you need... is based on your local building code. Where we are based a 1,000 ft2 single family home with 2-3 bedrooms would require only 45 CFM of fresh air so you would need the smallest ERV you can find. You are allowed to bring in extra outside air if you want to further improve ventilation, but it will equate to more compressor based cooling and dehumidification needing to maintain comfort than a smaller ERV.
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The best explanation I’ve seen of this technology!
This was an excellent presentation with a live demonstration. Cleared all my doubts.
This man offers high level presentation great video production
Great demonstration. Surprising how well the heat transfers. Thank you!
I've been trying to fully understand HRVs ERVs for months and although I got to where I understood what they did, I had no idea of how they did it. Of the dozens of videos I've watched, your video is the ONLY one I've found that gave me the information I wanted. Excellent job!!
Thank you. If you want to dive deeper, we did a 1.5 hour webinar on this same topic today. You can watch it at attendee.gotowebinar.com/register/3857937118863671564
@@TECTubefilms
Awesome! I'll definitely check it out, but it will be 2 or 3 days from now. Unless I flake out on my responsibilities, then it will be sooner, so it'll probably be sooner...
Best explanation I've seen of what an ERV is and does.
This video as really good at explaining ERVs. My HVACR class stumbled across you video of the psychrometric chart and it was very informative. I have copied this link and shared it with my instructor because I feel like our class will benefit from this training as well. Thank you for your videos and I look forward to viewing more of your content as needed.
Great demo, i'd love to see a video with smoke passing through the box to show the air paths.
Really appreciate that HRV model in the end with clear explanation!
The best video I've seen to explain ERV. Congrats
Thank you for the video. I never came across ERVs in my 8 year long career as a facilities maintenance manager. I came across this technology when I moved to a cold country last year and really wanted to know how they worked.
Ryan, Excellent explanation of ERVs and HRVs
Well done video. Clear explanations that a lay person can understand❤
Thank you for this video, excellent demonstration and explanation of the ERV, answered a lot of questions!
This is amazing! Thank you so much for the explanation! I think it’s the best video on TH-cam regarding the topic
Im from Malaysia and this video help me understanding the system with full of information. Thank you from 2022
I always assumed HRVs are a waste of money. But I live in Monterey Ca where the climate is mild and perfect. But this video explained it great. I can now see them being beneficial in extreme temps with extreme humidity where fresh air is important.
Really enjoyed the presentation style, thanks 👍👍
This is the best demonstration I have seen to explain the ERV function. I was surprised at how well the ERV was able to transfer temperature in the demo. I wonder if you could generate some steam at the outside air input and also see how well the humidity would be transferred using RH gauges in each chamber as well as thermometers. Also, it would be interesting to compare the efficiency difference from the rotating membrane compared to the usual home module.
There is plenty of data to illustrate the efficiency different between an enthalpy wheel and fixed plates.
Put wheels are only for commercial projects. No one makes a wheel small enough for residential.
Great video and explanation... thank you! I am impressed with the efficiency of the wheel!
Thanks for explaining this topic and the demo, much appreciated.
Well presented. Understood and now interested! Thanks!!!
Okay, that's magic. Crazy! Thanks for posting this.
Thanks! Great explanation. I was able to peak some design tips for my DIY ERV.
Very good explained even for those with English as a second language! Thank you and greetings from Germany!
Do you need to keep it on all times or only when you need it
Great video and wonderfully clear explanations. Thanks for doing this.
Good job explaining main principle and types
One of the best explanation👍
Thank you♥️
Great video! Thanks for making it easy to understand!
Awesome video! Explained very well, both theory and example! Thanks!
Best explanation on TH-cam ❤❤❤
That was VERY helpful to my understanding. Thank you!
Excellent explanation..congratulation brother
Look, I just stumbled across this video. I'm a network engineer and understood 0% of how A/C, ventilation, HVAC, etc worked. But this guy did a GREAT job explaining this! (*me yelling across the house* "Hey honey, you want me to explain to you how an ERV keeps a building cool?!") That's right, I'm that kind of nerd who MUST share facts about things i'm excited to learn. 😋🤣
Yea this guys explination is top notch! I couldnt make heads or tails of why this type of system is used or its purpose... Now I want 1! lmao Oh and dont worry the nerds will inherit the earth! :P
Awesome video! ASHRAE recommends as much as outside air as possible for COVID. This is great technology to have to allow taking mostly outside air even when it’s hot or cold outside without impacting energy usage or performance.
Snake oil
Great explanation of how these work.
very good. finally someone explained it well.
Very impressive vid. Keep up the quality. Will now have to research ERV's.
Blown away by how effective it works in that final demo. I'd expect to split the difference 50/50 on temperature at best, but it seems you're closer to 90% thermal energy rejection which is nuts.
For commercial systems, the minimum per most energy codes is 50% total recovery (sensible + latent). Most wheels are 65 to 75%, but some can be higher.
@@TECTubefilms Is there a difference between the efficiency of a wheel vs box style heat exchanger? Great video and demo btw 👍
Yes, per give area of space, a wheel generally trumps all other ERV types. For example, one of the manufacturers we use can run 30,000 CFM thru a wheel in a certain size cabinet. However, when they use that same exact cabinet chassis for a fixed plate ERV, they can only do a our 12,000 thru it.
Fantastic video guys; this will help with my power engineering exams :)
Thank you for your explanation, so the silca gel. Is it replaceable?
No, it does not need to be replaced. It is impregnated into the polymer. It doesn't wear off or anything like that.
Thanks a lot for this Awesome Video. Got a really Nice Idea of how these systems work.
lots of info, well presented, thanks!
This is an absolutely excellent video explanation. Close-ups, hands on, shows what's happening.
He mentioned an exhaust duct "from FURNACE to HRV, then vented outside" at 5:55. Is this true, or was this duct pulling exhaust from bathroom? I'm trying to understand how to tie into existing HVAC ducting.
Yes, in this particular ducting scenario (and there is more than one way to duct it), the HRV pulls air from the furnace return and exhausts it outside. It then pulls air from the outside and replaces it in that return duct. This is the easiest way to duct it, but it also doesn't save any energy. The best way... as you hinted at... would be to pull air from the bathroom instead of using a bath fan and run that thru the HRV instead of pulling return air. This is air you planned to throw away anyway so may as well reclaim energy from it.
@@TECTubefilms Ok interesting. Thank you. I'm less worried about energy, more worried about excessive redundant systems, ducting, and wall penetrations (bath fans, HRV, kitchen fans, makeup air, furnace, dryer ducts, etc).
Do they make enthalpy core boxes (without the HRV blowers) that can duct straight to the air handler using its central fan? To consolidate some of these duplications? Which vents can be combined?
I don't understand why we ditch the high CFM flow rates and high MERV filtration of an air handler for these tasks, and instead use these dinky little 100cfm central exchangers. In full redundancy no less.
@@slipperyslope3912 Pretty much the ONLY reason to install a HRV is to save energy. If you don't need/want the energy savings and just want fresh air, then there are several methods to duct outside air into the HVAC system without the expense of a HRV.
@@slipperyslope3912 No, we have never seen a residential size HRV without a fan. Just ducting it into the air handler would not work. The pressure drop of the HRV heat exchanger and filters is so high, that the air handler will just draw all of its air from the return duct and none from the HRV duct.
@@slipperyslope3912 You do not lose the MERV filtration with a HRV ducted into an air handler. The outside air coming thru the HRV is ducted into the return of the air handler upstream of the air handler's filter.
What a great presentation, well done.
I'm thinking of building an small HRV, is there an advantage to the wheel type vs fixed fins? Leaning towards fixed fins and doing multiple cross flow cores or a single counter flow as it would be easier to build, but the wheel ones are also kinda intriguing.
The advantage of a wheel is that it has significantly higher heat transfer ability for a given size of cabinet. The disadvantage of a wheel is if you need AHRI certification for zero crossover (aka EATR).
Very nice presentation. Thank you!
Thanks so much! You explained everything so well!
You described a dedicated HRV system for residential use. Typically these will be ducted to all the bathrooms as well as the kitchen (with a grease filter in place). Never a hallway like you said
That being said, most residential HRVs will not be installed like this.
You will just have your supply and return for your HRV tied into the return duct (3' apart) and an intake and exhaust going outside (6' apart)
We agree to pull air from the bathrooms as the first choice. If you need to pull more exhaust air (to balance with your required ventilation intake air) we would prefer to pull it from the kitchen (but not the hood) or from a general area like a hallway. We do not recommend pulling air from the kitchen hood since grease filters do not capture all of the grease, nor do homeowners change/clean them regularly.
We are not fans of pulling the air out of the furnace return duct to send thru the ERV and then outside. This is an energy waster. To make it an energy conservation device, you must recovery the energy from a waste stream... air that was leaving the house anyway even if you did not own an ERV.
You explained it so good. Keet it up...
I'm surprised the wheel spins that fast. I thought that each section of the wheel would need much more time to absorb the heat and change temperature before being able to transfer the heat to the other side. What material is the wheel and how is it able to transfer heat while spinning so fast?
We would consider this to be pretty slow. ERV wheels rotate at 10 to 60 RPM (similar to an old school record player), whereas a fan is rotating at 1,800 to 3,600 RPM.
This particular wheel is made of a polymer impregnated with a silica gel desiccant for moisture transfer.
In summer, hot moisture air is sucked from outside, and this hot energy is transferred to heat exchanger, there by the hot air losing it's energy to heat exchanger and converts to cold air which is then pushed inside the building space...and vice versa in winter...is it right?..pls confirm.
yes basically
@@TECTubefilms Thank You for confirming
In the UK we have humid winters, where ventilation is key to keeping the inside of homes warm and dry. Many people are talking about positive input ventilation (opposite of extractor fan just pumping fresh air into a central place to be blown through gaps of the building).. This increases heating cost as many units have a 500w duct heater to warm up the incoming air stream (~10c to -2c typically) and even then people complain of cold drafts from the unit.. I wonder if an HRV would help benefit.
Use the damp but warm exhaust from bathroom to preheat the incoming air somewhat..
Yes, you can run the bathroom exhaust through an HRV to reclaim the heat and transfer it to the incoming ventilation air to pre-heat that air less expensively.
Do not use an ERV in your application since that will also reclaim the moisture from the bathroom exhaust which it sounds like you do not want.
6:47 - if you want to learn the difference between HRV and ERV and how that works
In a residential ERV with the set of separator "fins" (at 6:15), my main point of confusion is why, after passing through the box, the temperature of the air entering the building isn't the same as the air going out of the building (the average temperature). I'd think the fins would take the average temperature of the air passing into the unit, and so exhaust air would be moderated and not so efficiently exchanged as it seems to be.
If we looked at a single fin (as a square), would we see a large heat difference across the surface of that fin? Is that how we're able to recover such a large amount of heat via the device?
The incoming air is not heated/cooled to the same temp as the outgoing air because the heat exchange process is imperfect. Depending on the model and type of heat exchanger, it can usually recover 55 to 85% of the available energy, but not all of it.
Not sure what is being asked in your second question
@@TECTubefilms Basically, the device is more efficient than I expected was possible from such a simple device. If the temperature was 20F outside and 70F inside, my prior guess was that the device would yield fresh air to the inside closer to the average of the two temperatures at 45F (with exhaust air at a similar temperature). Given that the heat recovery is in reality far more efficient than this, my assumption/guess is that the temperature is very different along different parts on each "fin" on the heat exchanger. (I'm not sure I can properly explain what I'm saying in a comment, as I'm discussing a 3D object in text only.)
@@dosadoodle If the temperature was only average of the two air streams, that would mean that it is a 50% effective heat transfer device. As mentioned, most are 55 to 85%. For commercial buildings, the minimum allowed per energy code (IECC) is 50% effective. There is no minimum for residential. The reason any heat exchange coil can be better than 50% is due to counterflow arrangement. If you want to dive deep into the technology on how ERV heat transfer works, you may want to check out one of our recorded webinars such as attendee.gotowebinar.com/register/6256885680768066575
@@TECTubefilms Thanks for the additional explanations and link to that presentation! It was interesting and helpful to listen to.
awesome video for explain two differences
There is a query I'll be grateful to get looked upon by experts like you. I was concerned that the temperature difference of the Air Streams going in and out (in case of an HRV) that could condense the water content in the humid air. Won't this happen and the condensed water will drip from the duct pipes?
Condensation can occur if one airstream's temp is below the dewpoint of the other airstream. Many HRVs have a condensation pan and drain line for this reason.
The ductwork between the HRV and the furnace should not condense, though. In order for that to happen, the duct temp would need to get below the dewpoint of the air in the room that contains the ducts. That will be difficult to do without refrigeration. Sometimes, however, this will occur on the ductwork between the HRV and the outdoors. Although that will happen on ductwork to the outdoors even if you do not have an HRV. The two ducts going to the outside should be insulated ducts like we showed on the HRV in the second half of this video.
@@TECTubefilms Thank you so much for the reply..
@@TECTubefilms where do I buy one of theses I am sick of my house being 94 degrees swamp cooler sucks
@@UPsideDOWNworld321 Are you saying you have a swamp cooler instead of an air conditioner (FYI - swamp cooler is slang for a type of cooling system used in desert climates). An ERV isn't going to help in that case. And ERV recovers heat/cool energy from your exhaust air and transfers it to your incoming ventilation air. Nothing more.
@@UPsideDOWNworld321 ERVs are available through just about any HVAC contractor
Very good demonstration. How are the heat molecules separated by that spinning wheel?
No molecules of the air are separated. The air molecules pass straight through the wheel. In regards to the heat... heat always moves from hot thing to cold thing, so if the air is warmer than the wheel, then the air heats the wheel. Then the wheel spins to the other airstream where the wheel is not the warm thing so it transfers its heat to that cooler airstream.
Just noticed your name. LOL
Fantastic explanation! Thank you very much!!
useful in the age of COVID when we want more fresh outside air coming in, and human exhalation going out of the building, without too much loss of heat or cooling
Great/fantastic/excellent video, love the plexiglass. I am looking for a similar system, but where the air exchanger could be bypass in spring & fall (hot days & cool night & since air is so cool at night, there would be no need to have the AC on). Am I missing something here? I can’t seem to find a system that does that.
Yes, most commercial ERVs have a bypass around the heat exchanger for "economizer days," since this is required now by IECC and most other energy codes.
perfect explanation.
dang didn't realize Richard Jefferson had a background in hvac
😂
It's Robbie Lawler bro
glad someone explained this.
Hard to believe it can transfer the heat that quickly. I want one it would be rough to get it installed.
Is there a measurement of how much energy is "lost" in this process? I realize that something can be derived based on that demo with the thermometers I am just curious if there have been papers/studies published on these.
Yes, but what do you mean by "lost?" Are you trying to figure out how much fan energy is being used to move this air? If that is the case, most selection software tools will tell you this kWh. Or are you trying to figure out how much heat is not being transferred that could be? If this is the case, then that is represented in the AHRI rated "effectiveness" percentage. Or are your trying to figure out how much leakage goes around the wheel on accident? This is represented by AHRI's measurements of OACF and EATR.
I heard about HRV just today, wow, why isn't this thing ubiquitous by now?! I also wonder the amount of energy needed to operate it.
Well... a HRV is not right for every application. It only saves energy if you already have a stream of exhaust air to recover from. And it only "pays back" if you have a lot of required outside air and the building is in an area with high utility costs. Where we are in northern Illinois, it starts making a lot of financial sense when the HVAC system requires more 1,000 CFM of outside air intake. If your building is in a state with more expensive energy costs, smaller HRVs can make sense too.
More over need maintenance mainly cleaning filters
This - coupled with gentle ceiling to floor airflow - would seem to be the future of viral transmission suppression in public spaces.
An ERV is a way to save the energy cost of ventilation air. It doesn't clean or purifier the air. It provides the same dilution affect that other ventilation system would also provide... it just does it with less heating/cooling energy.
If you are interested in viral transmission reduction in commercial buildings, check out our webinar on IAQ. register.gotowebinar.com/register/5473581496208425740
@@TECTubefilms I fully understand the function. My comment stands. I did not suggest that it cleans or purifies the air. Indeed, there is no way an HVAC system can filter viruses out of air transmitted directly from person to person in close proximity, even if filters could be so fine. My point is that in enclosed spaces with multiple occupants, the direction of airflow, its replacement frequency and dilution with fresh air are critical factors in reducing the concentration of pathogens in each breath of air we inhale. I was suggesting that individual occupants should have maximum supply of outside air to breathe - as opposed to air exhaled from others' lungs. This would seem to be accomplished by arranging airflow from floor to ceiling with fresh air constantly supplied with minimal turbulence. Energy recovery is required to make such a design economically practical beyond capital cost considerations.
@@TheCablebill Agreed. We have to tell people about 5 times per week that ERVs don't clean air, so I guess we just assumed that is what you meant. LOL
@@TheCablebill BTW - we do have a filtration system that filters viruses out of the air in an occupied space. We have been using these in hospitals for about 8 years. If you are interested in learning more, check out attendee.gotowebinar.com/register/2854708624619222797
Great explanations.Thank you sir👍
I have a question for you I just started working at a three story hotel I happen to go in the attic and found an ERV not running and hasn't been in awhile we have ducted energy on the first floor and Ptac units in all the rooms would it be wise to get the ERV running again to save energy cost or not ?
@techtube
What is the percentage that building exhaust air can go as carryover back to building?
It depends on the classification of the air in the exhaust and the specific local mechanical code. For example, if it is general exhaust and you are under IMC, then usually 10% can be recirculated from exhaust back into supply... or what AHRI calls Exhaust Air Transfer Ration (EATR). Other classes of air can be 5% or 0% in IMC.
struggling to grasp until very end. very helpful
What should the house exterior intake cover look like? We have a 8"x 8" bug screen with louvred flaps, but someone pointed out that it should be a boot cover, so that the outside air coming in is not impeded by the closed louvre flaps. Does it matter? Thank you, great video!
If the flaps are closed when the ERV is running then yes it matters.
We have a huge one in our building's air handling unit. We are seeing only about 8-10 degree drop from supply air temp before it hits our chilled water coil. In our area, our summers can be quite hot (100+) and seeing your demonstration, I am wondering if our wheel is not doing what it's supposed to! hmmm
Lots of possible issues: wheel could be dirty, you may not have enough exhaust CFM relative to supply CFM, your exhaust air may be too warm, wheel could be moving the wrong speed
@@TECTubefilms Ok. I have noticed that our exhaust CFM, when raised, the evap cooler does lower the supply, however, it creates negative pressure in our building. I will have to check the wheel's RPM as it was recently installed after our original wheel feel apart. Thanks for the feedback!
@@FloresEsteban1979 Wow! Your wheel fell apart? We have never heard of anything like that. Who was the original wheel manufacturer? Did you replace it with a different brand of wheel?
@@FloresEsteban1979 What is the exhaust air CFM and the outside air supply CFM? Are there other sources of exhaust in the building? If you want the space balanced instead of negative... and most buildings do... you need to move all of the building's exhaust air through the ERV and not use other exhaust fans.
@@TECTubefilms Yes, it was designed to have some positive pressure. The normal CFM during a regular business day is around 800-900 Exhaust and 7000 Supply at the air handler.
Where can you get a small ERV like that "demo" one at 6:49?
Call your local Carrier Dealer.
Good video and information. So can you have residential type hrv in an office setting?
You "could" but a residential size HRV in an office building, but it would not be large enough. The HRV should be sized based on the exhaust and outside CFM flows that the building was designed for. Residential ERVs are generally under 300 CFM, which would be very small for a regular office building. Unless you are talking about a small business office with just 10 people.
Tec Tube thanks
great demo and info!
Im thinking put stale intake for ERV in bathroom and above range. Could the fans be done away with? How many CFM per square ft? I saw another video it had U.S. divided into HRV or ERV. I live in ERV area but about 40 miles to HRV suggested area. Would it be beneficial to get a HRV
Yes, you can run bathroom air thru an ERV. We would not recommend you run air from the range. It has grease that you do not want to get on the ERV's heat exchanger. So use exhaust air from bathrooms and maybe a general area of the kitchen or a hallway. In this case you would completely eliminate the bath fans and just have a grill in the bathroom ceilings that duct to the ERV. Then have the ERV supply fresh air to the bedrooms and living room or have it bring the fresh air to the return duct for the furnace or main air handler.
From homes an ERV is almost always better than a HRV because it recovers moisture, as well. This keep moisture out in the summer and keeps it in during the winter. The reason there are maps to show not using ERVs in northern climates is because the ERV can develop frost on it from that moisture. Larger commercial ERVs have controls and/or heaters to avoid that, but that is not cost effective for small residential ERVs. So as you get to colder climates, you need to use a HRV for homes. The border for HRV vs ERV is specific to each manufacturer and their heat exchanger technology. So you need to look at the map specific to the model of ERV you are considering.
Very good video, thanks. Does air flow through the wheel style heat exchanger (enthalpy wheel?) or across it? Are they available to diy'ers anywhere?
The air flows through it
Not sure how to answer your question about installing one yourself. You would need knowledge of HVAC design/sizing, sheetmetal working, and electrical wiring, and in some states/municipalities licenses to do work in those trades. Plus the smallest enthalpy wheels on the market are too large for homes. Residential applications would us the enthalpy core style.
Hello, I have a barndominium home that has spray foam insulation. The SPF is not allowing any fresh air into the home and it off gasses some during the summertime. My goal is to bring in fresh air to help with the off gassing. Which of the 2 devices would help me better, an ERV or whole house ventilator with dehumidifier? Also, does the ERV only work when the HVAC system is running? Thank you for your time.
The ERV will be less expensive to operate. The dehumidifier can remove moisture from both the indoor air and the incoming outside air. The ERV will only remove moisture from the incoming outside air.
I love the ERV demo unit, makes it simple to see during the summer months how the temp exchange works. I wonder if you have made a video with this reversed, showing the intake/exhaust during winter month where cold air is being introduced to the inside? I recently built an air tight house and do not have any type of ventilation system installed, hence it's drawing from the windows and doors creating a vapor in the cracks. I also have humidity levels that are running between 60-70% showing on my thermostat, btw I live in Alabama. I'm thinking I need an ERV to help bring in fresh air to balance things. Will this also help to lower my humidity level?
No, we did not make a winter video. However, it would do the same thing as the demo in this video. Just move the labels around. Instead of the warm air being labelled as "outside air," it would be "return air."
An ERV will only help with indoor humidity issues if the humidity is being caused by outside air coming in. When the ERV brings in the outside air in the summer, it transfers the heat and the moisture to the exiting exhaust air so it does not come back in.
However, if the source of your high humidity is something inside the house, then an ERV will make the problem worse since it will transfer the humidity from the return air back into the supply air.
So the first question with any humidity issue is "what is the source of the moisture?"
There are lots of things you can do to deal with high indoor humidity. This would be an abbreviated list from best to worst (the list changes though based on WHY you have high humidity).
1) eliminate moisture sources (put caps on sump and ejector pits, run bath fan when showering, etc)
2) Right-size the A/C. 99% of all system are oversized and more than half are grossly oversized. The smaller the A/C capacity, the longer the run cycle, and hence the better the dehumidification
3) Multi-stage A/C. This also keeps the system running and the evaporator dehumidifying
4) Lower blower speed for regular A/C mode
5) On demand dehumidification using the A/C and lowering the blower speed even lower than regular A/C mode
6) On demand dehumidification using the A/C but not lowering blower speed further because the system is too basic to do that
7) Slightly larger evaporator coil with more surface area
8) dehumidifier
You should note that some of the decisions above affect other stuff so should not be modified without research. For example, you may lower blower speed to dehumidify better but then realize you have a crappy duct system and can no longer get enough air to certain rooms.
Great video! What happens if its warm inside the house and you want to have the cold air outside to cool your house. That is the scenario in tropical countries where at night time it is usually colder outside than inside. Can I still pump in fresh air at the same time make inside the house cooler?
That scenario occurs frequently in commercial buildings so the units include an automated bypass which allows air to run thru the ERV fans and duct without going thru the actual heat exchanger. This is in place of the economizer that most standard commercial HVAC air handlers have. Small residential ERVs do not typically have a bypass, just like residential HVAC systems do not have economizers systems. The first cost is too high in residential for the energy cost benefit.
a mixing box would be perfect for residential applications. It brings in cooler dryer air from the outside and lowers the energy load on your cooling system .
In a core-style residential unit like you showed, is it possible to turn an ERV into an HRV (or vice versa) simply by changing the core from one with a metal heat exchanger to a polymer heat exchanger (or vice versa)?
Yes, that is possible as long as your model has a drain. Lifebreath used to offer this option, but not sure if they still do.
Question: when the hvac system is not running should the ERV be off? there would be not benefit to have it on while the system is off?
If the ERV is ducted into the main HVAC system, then they should be on/off together. Keep in mind that ventilation in a commercial building is required constantly, hence both the ERV and HVAC need to be on, during the buildings occupied hours.
@TECTubefilms thanks for the reply that's what I thought was the case for my ducted system for my residence. The builder told everyone in my neighborhood that it needs to be on 24/7 and taped the switch on. We are not in a high humidity zone (cen California).
@@hctibeyb1788 The climate won't affect the code requirement to run the system 24/7 or not. Modern residential, like commercial for a long time, requires continuous ventilation.
This was such a great video to understand ERV technology. The demo unit with the thermometers makes it that much better. Thanks so much!
I am having hall with entry 13x11 feet with length 67 feet and width 37 and height 14 feet please give your best advice for.air ventilation
Would you say the ERV runs 24/7 in a residential application? My load calcs are calling for 84cfm so we assume that's constant.
If not too complex for your controls scheme, we would suggest running it when the home is occupied. Many smart thermostats can handle that. Or if not, you can at least tie the ERV to run off the EAC terminals of the furnace so it is engaged when the main fan is engaged... and then program your fan to run constant during occupied hours and intermittent during unoccupied.
Where do I get the wheel? Can I make my own wheel? And how well does the seal between the spinning wheel have to be? Do you have a miniature version of this system for a small 2 bedroom house?
The wheel in this video is the miniature version. Wheels are only used in commercial ERVs which range from about 500 to 50,000 CFM. Some of these are 10 ft in diameter. However, if you really want, Airxchange does make one down to just 50 CFM, but it would be very cost prohibitive to build a residential sized version with that wheel. For those small sizes, it would be less expensive and more reliable to use a "packaged" residential ERV which normally has an enthalpy core instead of a wheel and motor.
You do not need to seal between the wheel and the cabinet... in fact you really cannot because the wheel is in motion. However, by properly positing the two fans for pressure control, you can insure minimal to zero leakage for EATR and OACF. You may want to check out this webinar if you want to learn more about ERVs and wheels - attendee.gotowebinar.com/register/3857937118863671564
with an EVR does that mean i dont need a seer 16 unit because a seer 14 can work just as good with an EVR? in 110F weather ?
An ERV only saves the energy associated with conditioning your ventilation air. It has no relation to the cooling energy which is represented by the SEER rating.
@@TECTubefilms so it makes conitioned or heated ventliated air stay cooling or warmer longer so I stay comfortable longer and ac doesnt have to kick on so often ?
@@joeydelmarsjr.646 We suppose you could think of it like that. It makes the ventilation air from outside cooler as it comes into the house during the summer (and warmer in the winter) for nearly no energy cost. Hence this would allow your A/C to not run as much if that is what you were previously using to cool your outside air. It will also dehumidify (summer) or humidify (winter) that incoming outside air and that will certainly improve occupant comfort.
If I wanted a system to reduce building/room air humidity as much as possible for a specific production purpose but keep the heat in, which one would I want?
If the moisture is being introduced by outside air coming into the building via the ventilation system, then you would want an ERV. If the moisture is due to indoor sources (pool, people, fountains, etc) then you would want a HRV.
@@TECTubefilms Thank you. Sounds like I need an HRV.
Very informative. Thank you
How much do these things actually save you though. I'm in Canada and wonder by how many degrees the air temp is being heated or cooled?
razz P
It basically recovers heat from the indoor air as it replaces the indoor air with the outdoor air. It's just an indoor quality improvement device. Keeps indoor air fresh without the added cost of cooling it or heating it, depending on the season. Hope that helps.
Guess it be a hard question to answer. But curious how many celsius is the coming in air heated by? Guess the ultimate savings would be to not use the HVR/EVR, and just recirculate stale air. :). I assume HVR only need to be on while people are in home?
ERVs save energy if you have a stream of exhaust air to recover energy from. So if you already have sources of exhaust air (such as bathrooms, pressurization control fans, etc), instead of throwing that conditioned air away, you can first save its energy. The amount of energy savings... and more importantly, the amount of dollars saved, depend on the specifics of the project and the utility costs.
Does anyone know the manufacturer of the ERV?
The commercial ERV in the video is from MicorMetl and uses an Airxchange wheel. The residential fixed plate ERV is from Lifebreath. The clear demo module uses and Airchange wheel also.
Now I'm clear on how Erv works. Previously I got a lot of confusion on erv's
AMNJIRI
i’m replacing the capacitor on the fan, after the erv has been inactive for a couple years. there is some corrosion too. the fan spins, but it is like a bike wheel where there is contact with a brake pad, rather than a smooth spin that keeps going after released. how easily should the fan spin?
(oh, this is when i try to spin it by my fingers with the unit unplugged. i haven’t connected the capacitor yet)
It might be a "sweeper" that is slowing it down. That is a little brush like you have under your exterior doors. It is there to reduce inadvertent transfer. But in any case, you need to figure out what is slowing the wheel down when you spin it by hand and then decide if that is supposed to be there or not.
Silica beads are used as desiccant in thermal pane windows, but they eventually become saturated. Doesn't the silica-gel wheel eventually become saturated? I know it will vary with a number of factors but how often might one have to be changed? Annually? Bi-annually? Every two years?
No, they do not become saturated. They are "dried" as the wheel cycles into the other airstream which has a lower moisture content. In this application they only temporarily absorb water vapor for the purpose of transferring it to be released seconds later.
Neither the wheel, nor the silica gel impregnated into it, need to be changed at all. The life span is over 20 years, which will outlive the sheetmetal air handler that it is typically mounted in.
How can the enthalpy core possibly transfer moisture from one stream to the other without transferring bacteria and toxins with it? Moisture is water? I can understand the core transferring heat without mixing airstreams but moisture. I am just not sure how that works.
We suppose the simple answer is that the enthalpy core wicks the moisture through the media. This allows it to move moisture but not air. If there was something in the moisture... and that something was smaller that a grain of moisture, we suppose that something would also get pulled through. The IMC allows either 5 or 10% leakage of air from the exhaust to the supply depending on the category of exhaust air used in the ERV. What you are describing would be tenths of a percent, so it would be of no concern. Plus if you think about it, the supply air is going back into the same room(s) that the exhaust air came from in most applications.
Absolute thermodynamic witchcraft.
What is the material of the fan in the demo unit? Is it a metal sheet?
And when we turn it on, the motor on both ends are the one pulling the air making the middle turbine moves by itself?
(Wanting to make one for the house) please help :)
No, it is not metal. The heat transfer wheel is a polymer impregnated with silica gel desiccant to allow moisture transfer, as well as heat. This type of ERV is not cost effective for small systems less than about 1,500 CFM. Residential only needs 60 to 120 CFM of outside air so in those applications we use entahlpy cores for heat transfer instead.
The two fans are to move air in and out of a building... you are exchanging heat and moisture between them. They do not make the heat transfer wheel (what you called a turbine) move. That is moved with a fractional hp motor and a polymer belt.
What capacity do I need to cool a humid 1000 square foot house?
ERVs do not cool buildings, nor do they dehumidify them. The only thing they can do to help with heating and cooling is use your exhaust air to pre-cool and pre-dehumidify your ventilation air coming. The amount of ventilation air you need to bring in... and hence how large of an ERV you need... is based on your local building code. Where we are based a 1,000 ft2 single family home with 2-3 bedrooms would require only 45 CFM of fresh air so you would need the smallest ERV you can find. You are allowed to bring in extra outside air if you want to further improve ventilation, but it will equate to more compressor based cooling and dehumidification needing to maintain comfort than a smaller ERV.
Very good video!!! Thanks!!