Supply/return ducts


Old 07-06-14, 01:29 PM
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Supply/return ducts

I am going to install a new Goodman 2 ton split system HVAC that I have already purchased in a newly built residential work shop in Texas (hot climate) that I built by myself, no subs or helpers. I use the shop for restoring antique cars. Here is the scoop on the building construction
1. 22 x 38 rectangle building, exterior was wrapped in 1/2 OSB, 2 layers of building wrap, with 2 stone VENEER
2. 8' ceilings with concrete floor
3. 7/12 hip roof
4. bottom joist (2x12's) are decked with 5/8 plywood for storage in attic
5. there are no interior walls that subdivide any area with no plans to do such
6. building is standard IRC constructed with a hip roof
7. 4-3040 windows
8. 1 3068 service door
9. 2 - 7'x8' overhead insulated doors (don't know r factor) with weather stripping
10. 3 ' wall insulation (faced) r13 and 10 ceiling(faced) insulation r30
11. 1/2 sheet rock walls
12. eave vents every 6' and a 16' ridge vent is installed
HVAC EQUIPMENT 2 Ton 13 Seer Goodman Heat Pump System - GSZ130241 ARUF24B14
1. Air handler/coil is placed as horizontal unit LEFT in the attic with secondary condensation pan
2. all electric system with heat pump
3. Air handler is capable of 1150, 890 or 640 cfm depending on wire tap you use
4. 24000 cooling btu
5. R-401A system
6. Will be using flex duct off of plenums for supply and return
7. As I need the attic for storage, if possible I need to run the flex duct down the sides up next to (or at least very close) to the rafters. Storage is very much needed for car parts.
Question, finally
I am looking for optimal vent/register sizing and placement for both return and supply air. I have yet to construct the plenums but plan on using start collars and cement to seal all joints, seams, etc. I have replaced several units over the years and am very familiar with the process of evacuating the system, brazing copper, start up etc.. and electrical is no problem as well. What I have never done is design any of the duct work and really don't want to learn that side of the system. So placing and sizing of duct is what I need to know with system being optimally sized as opposed to undersized. Noise from high speed fan and/or air from supply or return vents is no problem, I just want to stay cool. I will call a good local HVAC person to come and check the system after I finish installation to see if it needs to be tweeked. I prefer the vents to blow hard, no matter the noise, if that helps to assist you in the size and location of ducts/registers. Any help is greatly appreciated.
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Old 07-07-14, 04:31 AM
airman.1994's Avatar
Join Date: Dec 2005
Location: VA
Posts: 5,767
Received 4 Votes on 4 Posts
Did you do a heat load? If so some of them will help you with this. If not its sounds like a basic design. Four - six supply drops will be plenty for 800 cfm

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