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-   -   HVAC duct sizing (http://www.diychatroom.com/f17/hvac-duct-sizing-170426/)

Blueraider 01-28-2013 09:15 PM

HVAC duct sizing
 
Just need to check to see if I'm right regarding my thoughts for a furnance install in my shop. Here goes.

Shop is 30 x 56 18 ft walls pole barn, metal skin,lightly insulated
Furnace 80%+ 96K btu, 4 ton blower. factory fan set med high (approx 1700 cfm no AC, Im installing horizontally midway long wall 8 feet off the floor.

I have same size insulated ducts Im using as return air and supply plenum, both are 20 X16 Hey they were free.

Return Ill have two 12 inch flex from the "plenum" running along trusses down opposite wall no grills. one run about 40 feet the other 50.

Supply will have two "mains" off supply using flex. 10inch 90elbow to 4ft flex to 10inch tee reduced to 8inch to 8 ft of flex to 8inch tee reduced to 6inch then 8ft of flex to 6inch tee capped. next "main" is 8inch elbow 2ft of flex to 8inch tee reduced to 6inch to 6 feet of flex to tee capped.

Need a little check to see if this works. Thanks

beenthere 01-28-2013 10:11 PM

Returns and supplies too small.

Returns for their length should be 16". But you could get away with 14".

Supplies should also be 14" to start with, then maybe an 8" supply with the trunk continuing in 12 then another 8" supply, and then the trunk 10" and let it be the last supply.


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