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Community and Q&A

What to look for in an ERV?

MSSUSR9501 | Posted in Mechanicals on

Looking for info on how to select an ERV and how to coordinate/integrate with other existing mechanical systems.  I am doing a significant main floor remodel in a 30 year old home.
Part of my goal is to make the home more efficient and comfortable. Ideally the selected ERV will be able to interact with the existing heat pump or a future heat pump and will be relatively efficient in operation.
At the moment I am looking at the RenewAire EV Premium M.  I plan to pull air from a master bathroom and a powder room and return the fresh air close to existing cold air return ducts.  Existing HVAC is a 3 ton Bard heat pump with an open loop.  Be nice if the two could “talk” to one another although I don’t really know what the benefit would be.
I have reviewed several of the existing ERV/HRV threads going back 3 or 4 years.  Tons of learning has occurred :).
What should I be thinking about when I evaluate ERV options?

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  1. Expert Member
    Akos | | #1

    You generally want an ECM blower and a unit with a hexagonal core.

    ECM blowers use about 1/2 the power of a standard motor which quickly adds up for something that is running 24/7.

    Hexagonal cores are counter flow (vs cross flow) which gives you between 10% to 15% efficiency improvement.

    For something plumed to the HVAC, I would also go for an autobalance unit, this way there is less chance of the air handler unbalancing the ERV when it is running. Plus an autobalance is much harder to commission improperly which is the biggest issue with any air exchanger install.

    I would also recommend installing an external filter box on the fresh air feed to the ERV. These tend to take much larger standard furnace filters which last longer, much cheaper than the ones built into the unit and can be swapped out for higher MERV if need.

  2. MSSUSR9501 | | #2

    Thanks, appreciate the suggestions. Most furnace filter boxes I have seen are not terribly airtight. Looks like the AC Infinity box might be a good fit for my application, it claims to accept standard 12x20x1 filters while the Fantech is limited to the Fantech filter.
    Presumably the filter does not add much load to the ERV fan as it pulls air through the filter.
    The ERV will be in the attic, conditioned space as the roof deck is foamed. Ideally the filter box would be close to the ERV as navigating the trusses in the attic is not an easy walk.

    I also saw your reply to another thread suggesting open grates from stale rooms to attic, then put ERV stale inlet in the attic. I need to see if that meets local code but that would address my desire to control attic humidity. Roof deck has about 5 inches of foam on it and house has been way more comfortable since the foam was installed.

    Thanks for sharing your knowledge and expertise.

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