Heating, Air Conditioning, Fridge, HVAC/Supply/return ducts


new shop
new shop  
I did have a huge data sheet on my new shop and system but the site kicks it back saying it is too long and involved. So, I'll try and shorten the question to get it through the system. I just finished building, by myself, no subs or help(not bad for 60 y.o.) a 22x38 shop at my house. Has 8' ceiling. No division walls or plan to have. Also has 4 windows, service door and two insulated garage doors. Bought 2 ton all electric Goodman heat pump/ac split system I am going to install. I have installed systems before but have no clue on duct work and would just like to get on with install. So, can you give me a starting point on size, placement and number of supply and return ducts? Thank you very much for any time you might have to spare for this question. Ron

Return grille: 20x20 H&C #672 (in a plenum base w/ unit in upflow configuration?).

Supply main: 16x8, reducing to 12x8 after four registers. Route the main along the center of the 38' dimension. Do provide a low resistance elbow from vertical to horizontal (radius heel AND THROAT or mitered w/ vanes). You'll need a 12" long transition from unit outlet to 16x8, have it made in a local shop. I'd insulate the duct with R4 "bubble wrap" to guard against condensation.

Supply registers: 12x4 H&C #682, eight required (four on each side of the duct); provide "sleeves" so the dampers don't protrude into the duct.

This arrangement will have very little resistance to flow, so you should set for the lowest fan speed.

Good luck!

Heating, Air Conditioning, Fridge, HVAC

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Fred Weldin


I can't help you if your whatsis won't work, people (Especially if it's a refrigerator); I have no experience with appliances, and I haven't been involved with H&AC service and repair since March 08, 1996 (Thank the Lord); I always send a "standard" reply to appliance questions and H&AC "Service and Repair" questions (about 20 a month), so if you want to know why your whatsis isn't working like it used to, ask someone else. A lot of my answers arenít read by the questioners; in that event, I always send reminders to read the answers for a month or more (the word "idiots" comes to mind - actually there's another more appropriate word, but discretion prevents its use here). If you have questions about how big a unit you need, if one room's warmer than the others, if you want an opinion oas to scope of work on bids received, etc. just ask. Do visit www.askweldin.com, there's a lot of good information on sizing, ductwork, efficiency, as well as some techniques accomplished DIY-ers can use to troubleshoot and improve their H&AC. Finally, I want to thank all of the kind, serious people whom I meet here: I enjoy working with you. My wife says I'm "snarky" from time to time; as for you others, please use your imagination as to the responses swirling on the snarky side of my brain when I read your questions.


53 years in the business. See www.askweldin.com


B of ME U of D 1965, numerous classes, seminars and a lot of "Hands On" learning since.

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