duct size

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Old 03-02-04, 04:38 AM
klarson8
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duct size

I am replacing a 3.5 ton heat pump split unit with a 4 ton heat pump package. It is 20 feet from the package unit to the old airhandler where I was going to tie into the existing "distributor" plenum. DOn't know if distributor is the right word, but it is the area that all ducting from the house is distributed from. Anyway, my question... What size duct should I use for the 20foot run? Can you see any drawbacks from doing it this way? If you ask why not go back with another split system, it is because I would have to tear up my floor to get the old air handler out and the new in. I didn't build the house

Other info: 3000 sq ft house, split level, 22 ducts +/-
 
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Old 03-02-04, 06:16 AM
Ed Imeduc's Avatar
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I dont think you should try and add 20 ft of duct to the A/C unit. How about the return air also . But 240sq " a 10"X24"is tight good would be 312sq" a 12X"26".

But with the in and out duct thats 40' of duct you want to add. Id say dont do it Cant you just change the inside coil and outdoor unit?ED
 
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Old 03-02-04, 06:52 AM
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I would have to tear up my floor to get the old air handler out and the new in. I didn't build the house
Is this in the basement or crawl space?

Lot of these newer system are smaller than the old ones. in the long run, split system is going to last longer than the packaged unit.

They should be able to "cut" up the system and remove it from wherever it is at.
 
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Old 03-02-04, 07:40 AM
klarson8
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duct size

Ed, Return air duct is only about 3 feet. It is taken at the same point as the old unit. It is drawn from a storage room that has returns run in to it from the rest of the house. So back to my original question.. What size duct should the supply be?
 
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Old 03-02-04, 08:40 AM
Ed Imeduc's Avatar
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Ed, Return air duct is only about 3 feet. It is taken at the same point as the old unit. It is drawn from a storage room that has returns run in to it from the rest of the house. So back to my original question.. What size duct should the supply be?

I dont think you should try and add 20 ft of duct to the A/C unit. . But 240sq " a 10"X24"is tight good would be 312sq" a 12X"26".
Out and in for 1600 cfm Try www.llbuildingproducts.com

ED
 
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Old 03-02-04, 09:39 AM
klarson8
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Thanks ed. Had a brainfart from your first post!
 
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