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new trane hvac system (how big should return be)

Posted by t_j_ames2003 (My Page) on
Tue, Dec 12, 06 at 9:44

I'm not an HVAC expert but I've recently had an HVAC system installed in my row home (Trane TUD080R furnace and 2TTX4030 condenser). The job is near complete and by chance I had a guy in there the other day not associated with the company who installed it who told me the return for the unit is too small. He also mentioned that the thermostat should be on the first floor and not the second (top) floor. He said the way it is not, the coils will freeze because the unit can't draw enough from the return.

Is there any way I can find out how big the return should be?


Follow-Up Postings:

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RE: new trane hvac system (how big should return be)

Duct you Later...


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RE: new trane hvac system (how big should return be)

I generally go by a minimum of 144 sq.in. per ton of cooling.
*Note* Your return can never be too big but it can be too small.


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RE: new trane hvac system (how big should return be)

Don't know but I have a 3-ton HP with two 20"x20" returns, a 2 ton HP upstairs with one 20"x30" return.


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RE: new trane hvac system (how big should return be)

Um, that's a lot of return filter area...
John


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RE: new trane hvac system (how big should return be)

" *Note* Your return can never be too big but it can be too small. "

Ughh.. If your return air is too big, it wont flow back to the unit properly and it can ice up the unit.
Plus your not pulling back the stale air into the system to cool it in the area you want to pull from. Your temp readings in that area will take way longer to cool or heat in the winter time.


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RE: new trane hvac system (how big should return be)

I have never ever in my life heard that happening from the return air being to big. How can having too much air available for the return freeze up your unit??


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RE: new trane hvac system (how big should return be)

144 sq in per ton is a minimum by code where I am located.I normally oversize to around 180 sq in per ton.You can not freeze up a system with to large of a return.Altough static pressure must be considered when sizing a return.Some systems have no return duct at all.


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RE: new trane hvac system (how big should return be)

There is a lot to proper ductwork design.
Below is a link to some basic ductwork design info.
udarrell _ 2007

Here is a link that might be useful: udarrell.com


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