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Due to spam filter I will try to split the post

DoRight's picture

Part I

New construction.

I would like to hire a contractor to install an electric heat pump and heat exchanger.  I would likely have them build and install the plenum (spelling?).  I would like to do the rest of the duct work myself.


Do (post #206505, reply #1 of 5)

So, do we have to read the other posts to find the question?

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


yes, IT appears I must (post #206505, reply #2 of 5)


IT appears I must split posts in order to get arround teh spam filter


So, aside from some (post #206505, reply #3 of 5)

technical difficulties, I believe your question to be: How do I design and install my distribution system after I pay a contractor to install the unit and supply plenum?

I have some questions for you - who sized the unit? by what means? Have you performed a room by room load calculation? Have you any idea how to determine the required air flow to meet a calculated load? Do you have access to the tools and materials necessary (an HVAC supply house that will sell to you on a cash basis)? You will need tubs of self-tapping sheetmetal screws and a large tub of mastic, take-offs, dampers, plenum, ducts, boots, adjustable elbows, good foil tape, duct wrap, panning, registers and grilles - most of which you can't find but a fraction of what you would need at the home center. Find a supply house.

I can tell you how I design a system. Run the heating and cooling loads for each room. Establish the design air flow required for each room. (NOTE: if you are lost at this point, you may want to consider paying a reputable professional to do these things for you). Layoout the system in a 1-line diagram. label each portion with the air flow that is required. Using a "ductulator" determine the minum size for the branch and trunks. I size supply trunks at no more than 0.1"/100', branches at no more than 0.08"/100' and returns at 0.05" per 100 equivalent feet of duct (be sure to include a return in every room you want to be comfortable).

Standard sizes for trunk lines are 8" deep x even numbers widths. 10" and 12" are available, but less readily. Round ducts come in 5, 6, 7 and 8" sizes which will cover 99% of the branches in a residence. Don't use 4" for anything other than a bathroom exhaust or appliance flue and don't use flex if you can avoid it.

Easy enough, right?

HVAC Duct Info (post #206505, reply #4 of 5)

Full disclosure, I work with Owens Corning, but I wanted to let you know we just revamped our HVAC site with a lot of tips and solutions revolving around HVAC, duct solutions and air ventilation.  Figured I'd post the link and try to help out!

Good luck!





OC Digital

Much better Adam!  I would (post #206505, reply #5 of 5)

Much better Adam!  I would spell out Owens Corning Digital, so you don't get confused with a computer store in Orange County.

YAY!  I love WYSISYG editing!  And Spellcheck!