Not sure how an ERV actually works? It seems magical, but it actually fairly simple. Join Ryan Hoger as he walks us through one. Music by www.bensound.com
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.
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
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.
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
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...
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.
That would be a good visual. In the meantime we will add two items: 1) ERVs are AHRI tested and the accidential recirc from return air back into the supply air is represented by the Exhaust Air Transfer Ratio (EATR) and it is often well under a half percent. Most mechanical codes require this number to be under either 5 or 10% depending on the class of exaust air on the project. 2) Locating the exhaust fan in the draw-thru position relative to the wheel minimizes the EATR.
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.
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).
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.
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.
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.
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.
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 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Awesome video so it’s safe to say that when you have a heat wheel your outside air damper should be at least 90% open and return should be at least 10% closed? Thanks advance for the response god bless!
No, that would not be safe to say. If you are talking about the OA damper bringing air into the ERV, that would normally be a 2-position damper that is fully closed when the space is unoccupied and ERV off or fully open when in use. Why would you choke it down? Unless it is a very small ERV and hence the fan speed is not adjustable and you need a damper for balancing purposes. But even then "at least 90% open" would still not be true.
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.
i like that but im not 100 percent sold its that efficient ...... u have no gaskets, seals between fresh air supply and return air, it could be leaking by..... just saying, im not 100 percent on that....
Each commercial ERV is rated and the results are published at www.ahridirectory.org. Two of the tested items are leakage. There is Exhaust Air Transfer Ration (EATR) and that is the percentage of CFM that leaks from the return back into the supply. This is highly dependent on fan position. The worst I have seen is 6%, but most are under 2% and many are nearly zero. The other is Outdoor Air Correction Factor (OACF) and this represents the leakage from the outside air into the exhaust.
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.
What I don’t understand is that an ERV does not dehumidifier your house however it is removing moisture from incoming air from outside. I’m wondering if this can help me remove humidity from my house regardless?
If your high humidity is being caused by your outside air ventilation intake, then yes an ERV will help. But if you have indoor humidity caused by other sources of moisture, it will not help you.
There are lots of things that can be done to improve indoor humidity: 1) right size the A/C so it is smaller and runs longer cycles 2) increase evaporator surface area 3) multiple stages of cool 4) decrease blow speed for cooling 5) decrease blower speed on a dehumidification call from stat 6) dehumidify on demand using stat 7) seal leaky building envelope 8) seal leaky ductwork in unconditioned spaces 9) use exhaust fans when showering and cooking 10) get a dehumidifier (this is the most expensive operating cost of the choices)
Bringing in outside air with a fan will make a house positive to reduce infiltration. Using an ERV is just one way to bring in that outside air. And if you duct the bathroom exhausts to the ERV instead of stealing return air, then the ERV will be the most energy efficient way to bring in that OA.
How can you not understand what I mean? I think what is happening is that not only is plexiglass a poor insulator but the large gaps between the edge of the plexiglass and the wheel are allowing indoor air to bypass directly back inside, as well as outdoor air to bypass directly back outside, skewing the temperatures. There’s no other possible way indoor inlet and outlet are almost the same temp. You need to add a smoke or something to the equation to ensure there’s good sealing between the wheel and plexiglass.
@@EricPeelMusic Insulation is nearly irrelevant when you are moving air at speed for short distance. There are no large gaps between the wheel assembly and the case. And even if there was, the positions of the two fans would generate positive and negative pressure at the points of reducing EATR (the rate at which air leaks from indoor back into supply air). This is not some new technology that we made up... these ERV wheels have been utilized for decades. In fact, the demo box in the video has been in our lab for almost 10 years and it was a traveling demo owned by a manufacturer prior to that. ERVs are also required by energy code for many commercial systems in 30+ states and at a MINUIMUM per IECC 2021 must be at least 60% recovery. ERVs are AHRI Certified and you can look up their performance at www.ahridirectory.org which includes over 2,000 models of certified models using wheels.
@@EricPeelMusic Your idea of using smoke or a tracer gas is a good one. We did not think of that when we made the video a few years ago. At the time, the goal was to demonstrate the heat exchange process. It was not to prove the cabinet was reasonably tight so we did not think of something like that.
@@EricPeelMusic If you would like to understand more about ERVs, cabinet leakage, and the ability to transfer 80% of the heat (and in some cases 99% for nearly equal temperatures), we do have several other videos you may want to watch. We will post the links here for your viewing.
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.
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.
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
We are based in the Midwest so we are not too familiar with contractors on the west coast. If this is for residential then www.carrier.com or www.bryant.com both have dealer finders where you can search by zip code. If this is for a commercial building, then those search tools will not help.
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.
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 ?
The best explanation I’ve seen of this technology!
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 this video, excellent demonstration and explanation of the ERV, answered a lot of questions!
Im from Malaysia and this video help me understanding the system with full of information. Thank you from 2022
The best video I've seen to explain ERV. Congrats
dang didn't realize Richard Jefferson had a background in hvac
😂
It's Robbie Lawler bro
Great explanation of how these work.
awesome video for explain two differences
glad someone explained this.
Great demo, i'd love to see a video with smoke passing through the box to show the air paths.
This man offers high level presentation great video production
Well presented. Understood and now interested! Thanks!!!
Great demonstration. Surprising how well the heat transfers. Thank you!
This was an excellent presentation with a live demonstration. Cleared all my doubts.
Thanks! Great explanation. I was able to peak some design tips for my DIY ERV.
Excellent explanation..congratulation brother
Ryan, Excellent explanation of ERVs and HRVs
6:47 - if you want to learn the difference between HRV and ERV and how that works
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
Thanks for explaining this topic and the demo, much appreciated.
Great video.
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.
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.
Absolute thermodynamic witchcraft.
This is amazing! Thank you so much for the explanation! I think it’s the best video on UA-cam regarding the topic
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.
That was VERY helpful to my understanding. 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.
Great video! Thanks for making it easy to understand!
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
9:00 run smoke through it, I'll bet a lot of air is going from top chamber to bottom / bottom to top instead of directly through
That would be a good visual. In the meantime we will add two items:
1) ERVs are AHRI tested and the accidential recirc from return air back into the supply air is represented by the Exhaust Air Transfer Ratio (EATR) and it is often well under a half percent. Most mechanical codes require this number to be under either 5 or 10% depending on the class of exaust air on the project.
2) Locating the exhaust fan in the draw-thru position relative to the wheel minimizes the EATR.
Awesome video! Explained very well, both theory and example! Thanks!
Okay, that's magic. Crazy! Thanks for posting this.
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.
Well done video. Clear explanations that a lay person can understand❤
Great video and explanation... thank you! I am impressed with the efficiency of the wheel!
lots of info, well presented, thanks!
Great video and wonderfully clear explanations. Thanks for doing this.
Great video! Thanks!
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).
Good job explaining main principle and types
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
Really enjoyed the presentation style, thanks 👍👍
very good. finally someone explained it well.
One of the best explanation👍
Thank you♥️
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.
Thanks bro super helpful!
You explained it so good. Keet it up...
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.
Very impressive vid. Keep up the quality. Will now have to research ERV's.
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.
Thanks a lot for this Awesome Video. Got a really Nice Idea of how these systems work.
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.
Fantastic video guys; this will help with my power engineering exams :)
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.
perfect explanation.
Really appreciate that HRV model in the end with clear explanation!
Very nice presentation. Thank you!
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.
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.
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.
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.
@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.
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.
Thank you so much video
Fantastic explanation! Thank you very much!!
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
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.
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
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.
Very good video!!! Thanks!!
Thanks awesome video
Awesome video so it’s safe to say that when you have a heat wheel your outside air damper should be at least 90% open and return should be at least 10% closed? Thanks advance for the response god bless!
No, that would not be safe to say. If you are talking about the OA damper bringing air into the ERV, that would normally be a 2-position damper that is fully closed when the space is unoccupied and ERV off or fully open when in use. Why would you choke it down? Unless it is a very small ERV and hence the fan speed is not adjustable and you need a damper for balancing purposes. But even then "at least 90% open" would still not be true.
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.
i like that but im not 100 percent sold its that efficient ...... u have no gaskets, seals between fresh air supply and return air, it could be leaking by..... just saying, im not 100 percent on that....
good video, im not complaining
Each commercial ERV is rated and the results are published at www.ahridirectory.org. Two of the tested items are leakage. There is Exhaust Air Transfer Ration (EATR) and that is the percentage of CFM that leaks from the return back into the supply. This is highly dependent on fan position. The worst I have seen is 6%, but most are under 2% and many are nearly zero. The other is Outdoor Air Correction Factor (OACF) and this represents the leakage from the outside air into the exhaust.
If you are interested, here is a free 1 hour webinar on this subject. attendee.gotowebinar.com/register/3857937118863671564
Very informative!
Great explanations.Thank you sir👍
great
Now I'm clear on how Erv works. Previously I got a lot of confusion on erv's
AMNJIRI
good explaination thank you
I finally understand it!
Hard to believe it can transfer the heat that quickly. I want one it would be rough to get it installed.
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
Great 👌👌👍👍
What I don’t understand is that an ERV does not dehumidifier your house however it is removing moisture from incoming air from outside. I’m wondering if this can help me remove humidity from my house regardless?
If your high humidity is being caused by your outside air ventilation intake, then yes an ERV will help. But if you have indoor humidity caused by other sources of moisture, it will not help you.
There are lots of things that can be done to improve indoor humidity:
1) right size the A/C so it is smaller and runs longer cycles
2) increase evaporator surface area
3) multiple stages of cool
4) decrease blow speed for cooling
5) decrease blower speed on a dehumidification call from stat
6) dehumidify on demand using stat
7) seal leaky building envelope
8) seal leaky ductwork in unconditioned spaces
9) use exhaust fans when showering and cooking
10) get a dehumidifier (this is the most expensive operating cost of the choices)
Tec Tube thanks
Can sam ERV make my house slightly positive so it can prevent infiltration?
Bringing in outside air with a fan will make a house positive to reduce infiltration. Using an ERV is just one way to bring in that outside air. And if you duct the bathroom exhausts to the ERV instead of stealing return air, then the ERV will be the most energy efficient way to bring in that OA.
Very informative. Thank you
I don’t understand how this can be so efficient. How can the indoor outlet possibly be only 2deg warmer than indoor inlet?
We are not sure what you mean. Thse are heat exchangers with a fairly large amount of surface area relative to delta T. Does that help?
How can you not understand what I mean? I think what is happening is that not only is plexiglass a poor insulator but the large gaps between the edge of the plexiglass and the wheel are allowing indoor air to bypass directly back inside, as well as outdoor air to bypass directly back outside, skewing the temperatures. There’s no other possible way indoor inlet and outlet are almost the same temp. You need to add a smoke or something to the equation to ensure there’s good sealing between the wheel and plexiglass.
@@EricPeelMusic Insulation is nearly irrelevant when you are moving air at speed for short distance. There are no large gaps between the wheel assembly and the case. And even if there was, the positions of the two fans would generate positive and negative pressure at the points of reducing EATR (the rate at which air leaks from indoor back into supply air). This is not some new technology that we made up... these ERV wheels have been utilized for decades. In fact, the demo box in the video has been in our lab for almost 10 years and it was a traveling demo owned by a manufacturer prior to that. ERVs are also required by energy code for many commercial systems in 30+ states and at a MINUIMUM per IECC 2021 must be at least 60% recovery. ERVs are AHRI Certified and you can look up their performance at www.ahridirectory.org which includes over 2,000 models of certified models using wheels.
@@EricPeelMusic Your idea of using smoke or a tracer gas is a good one. We did not think of that when we made the video a few years ago. At the time, the goal was to demonstrate the heat exchange process. It was not to prove the cabinet was reasonably tight so we did not think of something like that.
@@EricPeelMusic If you would like to understand more about ERVs, cabinet leakage, and the ability to transfer 80% of the heat (and in some cases 99% for nearly equal temperatures), we do have several other videos you may want to watch. We will post the links here for your viewing.
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.
Thaaank you
Best explanation on UA-cam ❤❤❤
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
Where can you get a small ERV like that "demo" one at 6:49?
Call your local Carrier Dealer.
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
Can you refer me to an AC company that can do the ERV installation? I'm in Whittier, CA area.
We are based in the Midwest so we are not too familiar with contractors on the west coast. If this is for residential then www.carrier.com or www.bryant.com both have dealer finders where you can search by zip code. If this is for a commercial building, then those search tools will not help.
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
Thank you!
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.
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 ?