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Thread: Enough Flow ?

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  1. #1
    Join Date
    Apr 2007
    Location
    North Ga.
    Posts
    7

    Enough Flow ?

    Have a single 2.5 ton a/h v/s and a 2 ton compressor.

    The fan speed is set at 350 cfm per ton or 700 cfm total.

    This is a 1 1/2 storey house w/ 1,000 s/f down & 600 s/f up stairs.(Spray Foam Insulation)

    To cool the upstairs, I have to all but close every supply duct damper that feeds the 1st. floor.---> 10 ea. 6" rigid pipe....( as a side note there are 3 ea. 8" return ducts on the 1st floor.)

    Supply ducts feeding the upstairs (dampers wide open) are as follows--->2ea. 8" rigid pipe, approx. 40' in length...and approx. 5 ea. 90 degree fittings on each duct.......also 1ea. 6" rigid pipe going upstairs.

    Upstairs there is 1ea. 10" return main trunk w/ 2ea. 8" pipe splitting off the main pulling air from the 2 bedrooms.

    With dampers positioned as they are, I get a 3 degree differential between up & downstairs



    My question is....With a educated guess (without doing a s/p test)with the 1st floor duct dampers being closed approx. 85 to 90% will this harm the system?

    thanks for any imformative response...

  2. #2
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Best guess is yes,it will harm it over time.

    Have it tested and see about some duct remediation ,for the second floor.
    Last edited by dash; 06-20-2008 at 04:58 PM.

  3. #3
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,910
    I'd guess yes also.

    Neither the compressor or the VS motor are going to last long like that.
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  4. #4
    Join Date
    Apr 2007
    Location
    North Ga.
    Posts
    7
    Thanks for the replys !

    Do you think if I opened all 10 of the 1st floor 6" supply dampers to approx 1/4 to 1/3 from fully closed position,

    that I would increase the airflow enough that I would be safe as far as static pressure or any thing else goes

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,910
    Guessing at that could cost you a compressor.

    Have the system checked and the ductwork corrected as needed. Compressor change outs aren't cheap.
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  6. #6
    Join Date
    Jun 2007
    Location
    Atlanta, GA
    Posts
    61
    You can rig it any way you want but the end result will be the same. An expensive motor module repair and(or) more expensive compressor. When all else fails do it right.

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