# A/C return ducts...



## 47741 (Jan 5, 2010)

Quick (sort of) A/C duct question.

I have a 5 ton A/C unit, not sure of the air handler- no markings..I currently have a 20x30 return in the ceiling and right next to it, on the lower wall a 12x36 return.

I was thinking of blocking the 12x36 off and running returns to the far corners of the 1 story house. (2400sf, but cut up floorplan) The two locations are about 28 and 45 feet away from the air handler/return box. What size duct and returns would you suggest? I am thinking flex duct pulled tight since thats everywhere in the house right now. I was guessing a 12x18 or 18x18 return in the ceiling at the new return locations. Maybe 8" or 10" duct back to the air handler? the 20x30 return is straight up into the box- no restrictions.

I know its more complex than this question makes it out to be, but I am trying to simplify it a little. 

Thanks for any ideas..


----------



## REDKILR (Apr 30, 2005)

Your already short grill area as it is.You need around another 400 sq.inches(16x25)What size duct do you have run to your existing r/a's?


----------



## 47741 (Jan 5, 2010)

You're saying I should have 1450 sq in for a 5 ton unit?

The r/d duct is 18", slightly ovaled, and probably a 1 foot run into a huge plenum box.


----------



## REDKILR (Apr 30, 2005)

More like 1350 sq.in.16x25 are more common and cheaper when you buy filters.An 18"is only about half of what you need on a 5 ton.I would demo that sidewall and add two more 16x25 r/a with a 14" duct running to each one.


----------



## 47741 (Jan 5, 2010)

Sounds good to me. I'll see about finding parts and such for that project. 

Would you suggest floor or ceiling returns? I was thinking going ceiling for ease and space, but I also read that the floor mounts are better for a/c systems versus ceiling. 

Or....would I be better off putting more, smaller returns throughout the house? Ceiling mount type.


----------



## REDKILR (Apr 30, 2005)

Go with ceiling r/a's.You could install the r/a's like I was talking about and install some 12x12 r/a's in the bedrooms and jump off the main r/a's for more comfort in the bedrooms.Use the cheap fiberglass filters and change out every month.Don't use the pleated filters,they cause too much drag on the system.If you decide to go with the 12x12's in the bedrooms,size your duct up one size than the supply.Hope this helps.


----------

