more duct or add 2nd unit? - http://www.hvacmechanic.com/ Forums
Original message
| chaztmo
 |  "more duct or add 2nd unit?"
, posted Mon 21 Jun 00:47  
My friend just moved into 4yr old home w/a 2-3yr old Winchester AC unit w/5 ton condensor. The system cools downstairs in seconds, is loud & has jet flow, BUT the 2nd floor is very warm. Out of the 2 vents in each 2nd flr rooms ceiling, the 2nd vent is wide open to attic (There is no return line to any of these rooms.) There are two 6" flex insul ducts that run up a shute supplying the cold air. I thought about re-routing one of those duct lines to all those empty return vents & making change down at unit, thinking he just needed better supply/return set-up? He had someone look at system and was told he needed another unit in attic, but I don't buy that because the 1st floor is like a jet engine and home is under 2000sq ft. Basement supply/return set-up isn't eloborate -- RETURN is just 5' tall and (4) 8" flex duct to the (4) return vents. SUPPLY is 20' long of 24" wide insul box w/(4) 6" flex duct to all (4) supply vents (plus the 2 shute ducts I mentioned earlier for 2nd flr). Am I on the right path to help him? p.s. Heat is totally seperate unit. Grateful for any advise!
chaztmo
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Replies:
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| cesarin78801
| "Re(1):more duct or add 2nd unit?" , posted Mon 21 Jun 07:40
the way you understand is that you have 6-6"flex duct lines running for a 5 ton system
and that is why you here the noisy air comming out of grilles you are trying to get 2000 cfm thruogh an air duct that can only carry about 700- 900cfm I don't have my ductculator but I send me the print and measurements of your apartment(blue print)and i will size it for you or give you a better idea of what to do remmember heat rises and you have one unit suppling the upstairs and downstairs you will need to try to balance the air for downstairs and upstairs
it is recommended to have 2 different units for a two story house because is very hard to keep same temperature downstairs and upstairs with one unit and one t-stat my e mail adress cesaryyjanet@yahoo.com
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| | chaztmo
| "Re(2):more duct or add 2nd unit?" , posted Wed 23 Jun 00:11
The first floor is supllied by a 20 feet X 24 inch X 10 inch supply duct that has two 6" flex duct lines off the very end and two more that branch out along that 20 foot run. The second floor is supplied by two 6" flex ducts that come off the top of the unit.
I have a very similar home but my system was installed during construction and is both heat and AC. My 2nd floor is always a little warmer but nothing like their home.
Any thoughts about those 2nd floor vents for return air in each room? Not one has a return line to it, which I think adds to the heat or cold depending on the season. It is like having 4 holes into the attic that are wide open all year long!
Would building bigger trunks for SUPPLY or RETURN help either floor?
Thanks
chaztmo
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