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ERV duct sizing for residential house

ken_o | Posted in Mechanicals on

I think I’ve read most everything I can find online, and yet, I’m still puzzled.  I’ve read Alison Bailes ductwork guides, and I think I understand TESP, ASP, TEL, FR, etc.  The ERV that sounds right for my house (still in planning) is a Lifebreath 130 ERVD. Ductwork will all be within the heated envelope.

If I follow Alison Bailes design methods (which really only seem to reference heating and cooling systems, but I assume they would also apply to dedicated ERV ductwork), I come up with a 6.5″ round or 3.5″ x 12″ rectangular trunk.  Most ERV/HRV diagrams show ductwork no bigger than the ports on the ERV/HRV unit.  Is a bigger trunk size unusual, or did I miscalculate or misinterpret something?  

Thanks for your thoughts.

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Replies

  1. Expert Member
    Akos | | #1

    This is not uncommon. When you end up with longer/complicated main trunk, you end up needing to upsize to stay within the pressure loss limits. You can sometimes re-design your ducting to avoid this by making some of your supply lines longer instead of the extra long main trunk.

    Put a reducer right at the unit and run the larger ducts.

  2. ken_o | | #2

    Thanks. That's the "vote of confidence" I needed. The ducts will fit OK, I just didn't want to pay for the bigger ducts if I didn't need them.

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