ERV duct sizing for residential house
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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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.
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.