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Community and Q&A

ERV – Continuous or Intermittent?

Roger_S39 | Posted in General Questions on

Is it better to run an ERV continuously or intermittently?

ERV model is:
Rheem/Protech 84-ERV180

Air Supply wall control model is:
Rheem/Protech 41-40210-01

The control only has a manual switch with the option of:

Could an ERV running continuously, even on low with a filter installed, result in occupants suffering from allergies due to too much exterior air being brought into a new construction home?

Thank you.

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  1. user-2310254 | | #1


    If you have a tight house, you need to keep it ventilated to avoid the build-up of indoor pollutants. (See for more info.) Of course, it is possible to over- or underventilate, so you have to keep an eye on humidity levels.

    As to your allergy question, this ERV seems to have a pretty minimal filter, so I wouldn't be surprised if it was sucking in a fair amount of pollen during allergy season. When I installed a ventilator/dehumidifier in my last house, the intake included a replaceable MERV filter. (I think it was a 2 inch.) But if this is new construction, I would be more suspicious of VOCs left over from the construction process. How long have you been in the house?


    I didn't see anything in the Protech documentation about additional filtration. Is your ERV tied into a forced air system?

    1. Roger_S39 | | #3

      It is not.

      Based on an article published on GBA, that discussed the different ducting methods for incoming and outgoing air for an ERV, it was installed with separate dedicated duct lines.

      Thoughts, please???

  2. Trevor_Lambert | | #2

    Continuous is better. Intermittent can certainly work, but it needs to be automatically controlled, as opposed to someone manually turning it off and on. The ventilation rate should be set based on removal of contaminants (principally carbon dioxide), not the limitation of introducing allergens. If the latter is a concern, it can be addressed with filtering the incoming air and also running an air purifier inside. There's no substitution for CO2 removal besides fresh air.

  3. Deleted | | #4


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