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Community and Q&A

ERV/HRV installations using forced-air space heating ducts

user-621079 | Posted in GBA Pro Help on

I am a HERS rater and EE building consultant. 40-50% of the new constructon I see utilizes an ERV/HRV for whole house ventilation. Of those, (roughly) half of those are installed in houses using ductwork for space heating and/or cooling. Of those many have the ERV/HRV houseside ports ducted into the return side of the duct. My question is: How reliable is the airflow strength of the ERV/HRV when the ERV is called to run, but the air handler unit fan is not running. (The call for heating / cooling and balanced ventilation is not always simultaneous) I’m reading footnote 15 of the ESTAR HVAC contractors checklist and thinking a Smart Cycler control (or equivalent) is required which will engage the air handler fan whenever the HRV is called. Will the Smart Cycler work in reverse and engage the HRV whenever the house calls for heating or cooling? Any feedback out there on the Smart Cycler or like control devices, Thanks for all your help.

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  1. user-723121 | | #1

    I think there is some concern in dropping cold HRV intake air in the return due to possible furnace heat exchanger interaction. I don't know if this valid or not as the HRV will warm the intake air to a large degree.

  2. GBA Editor
    Martin Holladay | | #2

    The answer to your question can be found by referring to HRV installation manuals or by talking to the technical rep of the HRV manufacturer. Most HRV manufacturers provide details for how to install their units in conjunction with furnace ductwork, and their controls are designed to allow for furnace interlock wiring that energizes the furnace blower when necessary.

    These types of installations have several drawbacks, including higher energy use and less precise control of cfm flows to individual rooms, compared to installations with dedicated ventilation ductwork.

    I am providing two details from a Venmar installation manual; of course, installation details may vary by manufacturer.

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