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Thread: ERV Install Questions // Exhaust and Fresh Air Connection Locations

  1. #1
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    ERV Install Questions // Exhaust and Fresh Air Connection Locations

    We live in a very basic 2 story Colonial style home in the Chicago area with a family room behind the attached garage. Our air handler is setup with a cold air return coming from one direction for the main portion of the house, and another cold air return coming from the crawlspace below the family room. When looking at the front of the air handler one return comes into the return plenum from the front and one from the rear.

    We're looking to add an ERV to the house, and the installers we've talked to want to attach the fresh air intake and exhaust to the cold air return in the crawlspace. This is most likely for ease of install since the unit will go in the crawl and outdoor exhaust and intake will be from the crawl as well.

    My concern with this install is that it would only be handling air from less than 25% of the house, while none of the return air from the main portion of the house (75% or greater) would be touched. My thought is that the exhaust should go on the side of the cold air return that serves the larger portion of the house. If they go that route is it ok to install the fresh air intake on the return from the other side that serves only the family room?

    We recently had the basement finished and the majority of the cold air return for the main portion of the house is now covered by drywall and framing, so access could be difficult.

    Thanks
    John

  2. #2
    Join Date
    Aug 2009
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    Beatrice, NE
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    How much air will the ERV be moving?

    Does the crawlspace sit under a central part of the house?

    My thought is add a return grill in a central location like a hall and pull all the exhaust air from there, or you could even spread it to multiple source points but it will cost more.

  3. #3
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    Jun 2003
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    Madison, WI/Cape Coral, FL
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    If you are going to ventilate a home properly, you need a fresh air change in 4-5 hours. With an ERV, you can add the natural infiltration and air change caused by the exhaust device like the kitchen hood, bath fans, and clothes drier.
    In a green grass climate like Chicago, you will also need supplemental dehumidification to maintain a healthy <50%RH throughout your home during high outdoor dew points.
    Giving credit to the ERV's ability to exchange a portion of the moisture from fresh air entering to the exhaust air plus the moisture from the occupants, you will need 3-4 lbs. of supplemental dehumidification to maintain 50%RH during envings and rainy days when the outdoor dew points are +60^F.

    ERV and a small whole house dehumidifier should be connected to the central a/c ducts to be able to circulate the dry, clean air throughout the home.

    If this makes sense to you, we can discuss the duct connections which are important.

    Keep us posted on whatever you do.

    Regards Teddy Bear
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  4. #4
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    Sep 2021
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    Thread Starter
    Thank you both for the replies. Here is some additional info.

    Our home with finished basement is approx. 2600 sq ft. Right now we're leaning towards the Honeywell VNT5150e1000. The crawlspace is below our family room, which is behind the attached garage, so no it is not really over a central part of the house. Our plan was to use the existing ductwork to run the ERV.

    The dehumidifier need makes complete sense, and it's something we've looked into as well and will plan for.

    In regards to connecting the ERV to existing ductwork, with cold air returns coming in to the air handler from both the front and back in a T pattern, does it matter which side we hook the fresh air intake and exhaust to? The return coming in from one side serves our entire upstairs with 4 bedrooms and 2 baths, as well as the majority of the 1st floor with living room, dining room/office, half bath, and part of the kitchen. The return coming in from the other side serves the family room, and part of the kitchen as it's an open floor plan in that area.

    Due to limited access to ductwork in the basement, installers want to put both the fresh air and exhaust into the return in the crawlspace which only serves the family room and part of the kitchen. Is this a bad setup since none of the bedroom air would be exhausted, or does it not matter which air gets exhausted as long as we're pulling out and drawing in a balanced amount?

    Thanks for the help
    John

  5. #5
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    Jun 2003
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    Madison, WI/Cape Coral, FL
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    A little slow to mix throughout the home but not a big problem. Hope that your a/c blower is a VS fan that has a low speed recirculate mode. You need a/c fan to circulate the fresh air throughout.

    Keep us posted.

    Regard Teddy Bear
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  6. #6
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    Sep 2021
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    Thread Starter
    Our HVAC contractor completed installation of an ERV yesterday, the Honeywell VNT5150. They went with the connections discussed above for exhaust and fresh air, but did not perform any connections to the air handler, or to our Ecobee3. If I would like the Ecobee to control the ERV, should I interlock it with the air handler, and what benefits does that provide? I currently have 2 open wires inside the air handler and at the Ecobee (brown and orange at both ends). Is this enough to wire to the Ecobee and interlock if wanted?

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