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  1. #1
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    Intermittent cooling

    My upstairs A/C, a 3.5 ton unit has started to intermittently fail to cool.
    I had a technician come over while the failure occurred and he opined that the suction line at the condenser seemed too warm. He explained that of the line is too warm the compressor will overheat and shutdown, causing the system to stop cooling.
    He suggested adding 1Lb of R22 as low freon the likely cause. The explanation made sense to me. He did that and the system started cooling.

    Unfortunately the problem reoccurred.
    So before I call anyone back here, I'd like to get a better reading of the problem, with your help.

    When the system is working the DeltaT is about 20F and cooling is adequate. I measured the pressures at liquid 255PSI and suction 78PSI. I also took readings and calculated the Subcool (17F) and Superheat (11F) both measured near condenser.
    When failing the pressure at the high side fluctuates between 200-225PSI and the suction side at 120-125PSI. During those times DeltaT is very low, 2-4F. Needless to say, the unit runs forever under these conditions. Reading 13A of current at compressor during failure.
    The explanation offered by the tech didn't confirm, I had the unit running for hours and the compressor never shut down (although it may have overheated?!).

    Your expert advice is very much appreciated.
    thanks

  2. #2
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    Thread Starter
    .

  3. #3
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    He’s partly correct but there’s a lot more to determining the correct refrigerant charge. Warm line is not one of them.

    I would request a more senior tech or a different contractor!

  4. #4
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    What kind of metering device does your system have and what was the inside temperature/RH%?

  5. #5
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    Quote Originally Posted by Makeitcold View Post
    What kind of metering device does your system have and what was the inside temperature/RH%?
    Piston; The inside temperature at the time of these readings was 78F. I am in Phoenix AZ, the humidity was about 35% at the time.

    Other details, in case you would like to know:The Condenser unit is YORK H2RC042S06A, installed ~2002.

  6. #6
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    If recip. compressor have senior Tech. pump it down to see what they get. That experienced tech should get some info by doing that.

    You didn’t mention what the OD temperature was when you had those pressures.

  7. #7
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    Quote Originally Posted by adrian62 View Post
    Piston; The inside temperature at the time of these readings was 78F. I am in Phoenix AZ, the humidity was about 35% at the time.

    Other details, in case you would like to know:The Condenser unit is YORK H2RC042S06A, installed ~2002.
    Did they check anything other than the refrigerant, maybe like the capacitor?
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  8. #8
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    Quote Originally Posted by Bazooka Joey View Post
    If recip. compressor have senior Tech. pump it down to see what they get. That experienced tech should get some info by doing that.

    You didn’t mention what the OD temperature was when you had those pressures.
    90F

  9. #9
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    Quote Originally Posted by Mr Bill View Post
    Did they check anything other than the refrigerant, maybe like the capacitor?
    Cap is good.

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