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ERV choice – please critique?

orange_cat | Posted in General Questions on

HVAC designer 1 proposed 3 reversomatic ERVs (1) Rerv-C100 and 2 Rerv-80.

There was some discussion of using Lifebreath HRV, but current proposal is for identical  Lifrebreath ERVs instead

Should I be concerned? This is for ERV shared with heating air ducts which are using this equipment package

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  1. Expert Member
    Akos | | #1

    You always want something with ECM motors, the operating cost of a PSC motor is about 2x which means even if more expensive, the payback is very quick. On that front the Metro 120 would be a pass right off the batt. Lifebreath does have ERV with ECM which would work (METRO 120 ERV-ECM).

    Neither unit is the pinnacle of efficiency but if they price is right the Reversomatic looks like the better part. I would not bother with the 80-mini and would use the C100 in for all locations, this way you also have one standard filter for all units.

  2. orange_cat | | #2

    Thank you very much.
    Is there a third option I should ask for (neither reversomatic nor lifebreath?)

  3. orange_cat | | #3

    A follow up question (1) I see that ECM reduces noise, but on another thread a silencer was suggested (Fantech LD6) when ERV was close to the bedroom (as is in my case). Should I ask for those as well?

    (2) ERV shares ducts with the air force AC/heat, but what happens when neither AC nor heat is on (I anticipate using in floor radiant heat much of the winter; relying on forced air only for ventilation.). Anything to worry about here?

    1. this_page_left_blank | | #4

      If it's not too late, you should switch to dedicated ducts for the ERV. It's a fat better way to do it. Shared ducts should be relegated to retrofits only, not new builds.

  4. orange_cat | | #5

    I do not know if separate ducts for ERV are recommended generally or for the specific use case I described, but at this point we cannot easily change it. I did try to look into this and got overwhelmed with seemingly opposing views (separate ducts vs same ducts).

    I have also looked at ventilating dehumidifiers but in zone 5 it seems inferior to ERV.

    I am curious at this stage if installing a standalone dehumidifier with own minimal ducts and steam humidifier (using the SAME minimal ducts) is a crazy idea? And if then can come out to share the same room grilles (ok, that is probably not likely).

    The idea is that both humidification and dehumidification may be needed not when the forced air heat pump is operating (for cool or hot air - cool because it is shoulder season, heat because radiant heat).
    I believe ERV (with a damper) can operate even if air handler is not operating. So that adds ventilation.
    I believe steam humidifier can operate even if air handler is not operating.
    But I do not think dehumidifier can operate (with ERV) without air handler operating - suggesting separate ducts?
    A separate minimal ducting (not in every room, may be 1-2 openings per floor) for dehumidifier/humidifier seem feasible?

  5. Expert Member
    Akos | | #6

    For smaller ERVs, you can't beat the price and performance for a Panasonic intellibalance 100. The nice part about this unit is that it auto balances which works much better when connected to an air handler. It is also much harder to mess up the balancing during commissioning.

    Most of the more efficient units are much larger and expensive which can quickly add up when you need more than one.

    If the ERV is connected into the return of the air handler you won't have noise issues. Noise problems are when you have it hard piped directly into a bedroom.

    Whit simplified ducted ERV, the ERV is interlocked with the fan on the air handler. Whenever the ERV runs, it will run the air handler to mix and deliver the fresh air to the house even if there is not heat/cool call.

    Dehumidification is most likely will only be needed to dry out construction moisture, you'll need more than one stand alone unit for the first year. After that you might still need something so I would make a spot for a stand alone dehumidifier in the utility room. I know people complain about the durability of these but I've had pretty good luck with them provided the filters and coil are kept clean.

    Steam humidifiers put out 100%RH at high temperature, if you put that into a duct, as soon as that duct cools it down even a bit, you'll get condensation, not the best idea. The only spot for a steam humidifier is into the return of the air handler where it can mix with house air.

    Generally the higher efficiency your ERV, the less humidification you need in the winter. With my 50% latent recovery unit, I find that I don't need to run one until it gets bellow -10C.

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