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  1. #1

    Help understanding my HVAC

    Recently I had a new HAVC installed my old one was 30 years old and the warranty company desided to replace it. The old one was a Rheem 3.0 ton split unit (I have a basement) with r22 refrigerant. The new one is a Payne PF4mn and ph14nb 3.5 ton and it is a 410(maybe 410a?) refrigerant. with replacing the outside unit and the inside unit we did not replace the thermostate. The square footage of the house is 1500 sq ft. I have two complaints and I am not sure what to do about it.

    1) The temp does not feel as cool with the new one as it did with the old one. My basement doesn't even feel as cool, but maybe its just more humid in my house than with the old unit ?

    2) I have to put my thermostat on 65 to get the temperature to be around 73(maybe this is cause the thermostat is old ?)

    I have measured the air going into the return which is around 75 and the air coming out the vent is around 54.

    - Maybe this is normal going from at r22 to a 410 ?
    - Maybe 410 does not deal with humitdity as well (I live in a highly humid area)?
    - Maybe I am being a cranky consumer ?

    Any ideas or suggestions would be great!



  2. #2
    Join Date
    Dec 2010
    On a Peninsula in NE NC
    my 1st question would be why change a 3 ton unit of 30yrs to a 3.5 ton unit? t stat is part of the system, you do not have a new system.
    It's hard to stop a Trane. but I have made one helluva living keeping them going.

  3. #3
    Join Date
    Apr 2012
    your system is to large.. very common......
    it was working.... played with it.... now its broke.... whats the going hourly rate for HVAC repair

  4. #4
    Southern Mech Because that's what was ordered by the warranty company. Carmon .... the System can be to large ?

  5. #5
    Join Date
    Oct 2010
    Anderson, South Carolina, United States
    Quote Originally Posted by joeyman View Post
    Southern Mech Because that's what was ordered by the warranty company. Carmon .... the System can be to large ?
    If its too large it won't run long enough to remove enough humidity to make it comfortable.

  6. #6
    Join Date
    Aug 2003
    Fort Worth, TX
    How cold did you keep the house with the old system? Did you have to do the same thing with the thermostat?
    Building Physics Rule #1: Hot flows to cold.

    Building Physics Rule #2:
    Higher air pressure moves toward lower air pressure

    Building Physics Rule #3:
    Higher moisture concentration moves toward lower moisture concentration.

  7. #7
    Join Date
    Jun 2005
    SW Wisconsin
    The square footage of the house is 1500 sq. ft. I have two complaints and I am not sure what to do about it.
    In a humid climate you don't want an oversized A/C; they should have run a load-calc on your 1500-sf home so the unit could have been sized right.
    What large city do you live near or in?

    I hope the blower is set for 350-CFM per ton of cooling, or 1225-CFM.

    You need a new tstat with a Swing differential temp-setting so you can set it for longer runtimes.
    Then get the air infiltration rate down to 0.375-Air changes per Hour (ACH), so humidity doesn't load-up during the longer off-time.

    A 21F indoor drop is okay.
    You need to check the air-temp coming off the condenser (if it exits through the top) to see if it conforms with mfg'ers rating...

    What seer is the condenser? With R-410A, 50% relative humidity indoors, the condenser air discharge temp at 80F indoors 95F outdoors should be around, 15F at 1400-CFM; 12.7F at 1225-CFM.

    At 75F indoors & 1400-CFM 10F; at 1225-CFM only 8F condenser temp-rise; higher than 50% RH will rise the condenser temp-rise, & lower the indoor temp-split which is 20F in all this listings.

    Just an idea of what Goodman data lists for: GSX130421B* / CA*F3642*6B*; NOT a Payne unit...

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