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Thread: DOAS

  1. #1
    Join Date
    Aug 2010
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    We are looking at installing a Zehnder HRV system for our DOAS requirement in Northern Cal. Title 24 issue. Anyone have experience with Zehnder or have other recommendations.

    We know the unit is expensive, but it looked superior to anything else we saw in Vegas last week at the ASHRAE show.


  2. #2
    Join Date
    Aug 2003
    Fort Worth, TX
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    For the audience:

    DOAS = Dedicated Outdoor Air System

    More or less an HVAC system that introduces 100% outdoor air into a building, but heats or cools this same air prior to doing so.

    Which leaves me a bit puzzled...(and is this a residential setting?)...if the building is using a DOAS, is the HRV primarily to exhaust indoor air? Typically HRVs bring in outdoor air and exhaust indoor air simultaneously, and do so with reduced loss or gain of humidity. With a DOAS, it seems there are now two units bringing in outdoor air....the DOAS and the HRV. Can you explain this arrangement better for us?
    Building Physics Rule #1: Hot flows to cold.

    Building Physics Rule #2:
    Higher air pressure moves toward lower air pressure

    Building Physics Rule #3:
    Higher moisture concentration moves toward lower moisture concentration.

  3. #3
    Join Date
    Aug 2010
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    Being a homeowner rather than a professional I probably used the wrong terminology. We are talking about using a HRV system to bring in outside air and exhaust house air. We are doing a radiant floor and will not have a forced air system. The HRV will be stand alone.

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