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  1. #1
    Join Date
    Jun 2008
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    Air return measurements - am I crazy?

    I have a two story 2500sq ft house in Delaware. I have a York heat pump
    system that I plan to replace. The upstairs is always hotter than the downstairs. I brought a TSI velocimeter home from work and measured the air flows going into the air returns throughout my house. I measured the size of the air returns and calculated a cfm for each air return. Then I totaled the whole house up and got about 970cfm. 600 of that cfm is going through the downstairs returns, leaving about 350 for the upstairs.
    I tried closing up some of the downstairs air returns partially and the cfm total for the upstairs started to improve.
    Does what I am doing make sense? Could I "balance" the split between upstairs and downstairs and improve the uniformity of temperature in the house? Will I be doing something wrong to close up partially the downstairs returns?
    I have alot of numbers that I could show if that would matter.
    Any help is appreciated. Thanks.

  2. #2
    Join Date
    Jan 2004
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    If you restrict the first floor returns by 200 CFM, teh upstairs returns won't increse by 200 CFMs.
    Due to duct leakage, and the duct resistance of the second floor return ducts.
    Would work some what better if you worked on getting more supply to the second floor.

    If you do a load calc, you can find out how much air those roomd need.
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  3. #3
    Join Date
    Apr 2008
    Princeton, NJ
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    My house in NJ is 2800 sq. ft. and I had a similar problem with the upstairs being 12 degrees hotter than the downstairs. I closed dampers (not registers) and left the fan on the run position (rather than the auto where it shuts off with the AC).....and my temperature adjusted with the upstairs being 2-3 degrees warmer instead of 12+. The BIG problem of doing this is my static pressure jumped way up to 1.1 (it was already high at 0.9.). since this high pressure costs me more in electric to run the fan and could shorten the fan life....I have decided to have some ducts enlarged, which is currently in process.

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