Register Temperatures

Old 07-05-05, 11:55 AM
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Register Temperatures

I have a 2400 sq ft two story home with one 5 ton Carrier a/c unit. House is two yrs old, plenty of insulation, radiant roof barrier, solar screens on front (West) side of house. Problem I am having is register temps in master bedroom that is upstairs. There are two registers, closest one to main trunk of a/c is 61 deg and the one furthest (about 15 ft away) struggles to get down to 68 deg. This with thermostat set on 75 deg. I have had unit serviced twice and it is properly charged, good airflow, ducts have been checked for leaks and nothing found. I checked the duct run for the register in question and it is probably close to 25-30 ft long! I checked for kinks and found one strap that looked a little tight so I loosened it up but still no change in temp reading. Would a duct run that long pick up that much heat?
It is standard 8" flex duct.

Any suggestions would be appreciated.
Old 07-05-05, 12:02 PM
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Location: Easton, PA
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Flex ducts should never be more than 25 feet long. The airflow is probably sluggish and if the insulation is R-4, it may pick up that much heat. You can try putting another 6" of fiberglass over the duct to prevent heatgain and keep the attic space ventilated with a power fan to keep temps as close to ambient as possible.


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