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Thread: Trane heat pump

  1. #1
    Join Date
    Jan 2005
    Posts
    3
    My 10 year old 3&1/2 ton Trane heat pump has got to where it requires 8 to 10 minutes of stop time before it will restart. Given this time it will restart, heat and run great. When the unit attempts to restart in less than 8 to
    10 minutes, it will kick the fuse box breaker or the compressor will make a rat-ta-ta-ta-ta-ta sound until i flip the thermostat to the off position. Letting it stay in the off position for 12 to 15 minutes and then fliping it to the heat position the unit will once again restart and run just fine. Any advise will be appreciated.
    bob burg

  2. #2
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,289
    Call for a good heat pump service tech. From what you describe you may have system that is equalizing slower than usual (stuck check valve or flowrater piston), or the compressor may need a hard start kit installed.

    IMO, if an older heat pump or straight cool unit needs a hard start kit installed, it indicates a history of other system problems, such as prior leaks, loss of refrigerant oil, compressor "slugging", etc. The compressor bearings are getting tighter, which requires more "umph" from a hard start kit to get the compressor going.

    Hopefully in your case it's an equalizing problem only.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  3. #3
    Join Date
    Jan 2005
    Posts
    3
    Thanks for reply
    Have had hard start kit installed. Have had new (Trane original part) equalizer valve installed. Can you tell me more about this flowrater piston? Thanks.
    bob burg

  4. #4
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,289
    "Equalizer valve" or reversing valve? The latter is the proper terminology for the device that shifts the refrigerant flow through the system for heating or cooling modes.

    In some heat pump systems, the piston metering device serves a dual purpose. In cooling mode it meters refrigerant to the evaporator as a straight cooling system would. In heating mode the force of the reversed refrigerant flow forces the piston off its seat and allows refrigerant to flow unmetered into the liquid line, back to another metering device in the outdoor unit.

    If the indoor piston was hanging up and not coming off its seat in heat mode, it would cause a high head pressure inside the evap and trip off the high pressure limit switch. So now I'm thinking that may not be your problem, which is hard starting of compressor possibly due to slow equalization.

    If your system has a thermostatic expansion valve (TXV), it may be of the variety that has a built-in check valve. In cooling it allows refrigerant to meter into the evap, in heating it allows flow to bypass the TXV. The outdoor unit may have one as well to meter refrigerant to the outdoor coil in heat mode. I would have to know if these TXV's are bleed or non-bleed type. Bleed type TXV's allow system equalization during the off cycle; non-bleeds do not. Since you're complaining of this problem in the heating season, I would look at the outdoor unit TXV to see if it is not allowing the system to equalize, thereby leaving an elevated head pressure on the compressor (I'm assuming you have a reciprocating compressor instead of a scroll).

    What your service technician should do is put gauges on the system, run the system a good while, then shut it off and watch the gauge needles. If they ever so slowly creep toward equalization, that's likely your problem. If they equalize within a reasonable amount of time and you still have a hard start problem, there's a different cause. The reason I'm leaning toward equalization being the culprit is because of the time factor your report. A compressor with no start assist installed should be able to restart after 4 to 5 minutes normally, not 8 or 10. With a hard start kit (the good kind, not the cheap KickStarts or PowerBoost jobs) you can bump that motor on and off at will, practically (though not recommended).
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  5. #5
    Join Date
    Jan 2005
    Posts
    3

    Trane trouble

    Thanks SHOPHOUND
    Your diagnosis was correct.
    Hooked up the gauge's. The unit WOULD NOT restart until the
    pressure droped to within 7 pounds of being equalized.
    Unfortunately it took 9 minutes to reach this point.
    Is there any other part, condition, reason or circumstance
    that could contribute to this slow equalization?
    Looked at my home owner's manual that came with the unit.
    The part # listed for the expansion valve is VAL 2193.
    The part # on the box the new valve came in is VAL 02370.
    Called the Trane parts depot where the new valve was purchased. They say VAL 02370 is the right replacement part. Is there any way i could double check to be sure they are right? Thanks.
    bob burg

  6. #6
    Join Date
    Sep 2002
    Posts
    1,389

    bob burg

    Is the outdoor coil real clean?

  7. #7
    Join Date
    Sep 2004
    Posts
    51

    Talking

    I think your 10 year old heat pump is about to kick the bucket if you already got a start kit on it. Check for proper operation of you start kit.Is it wired right? Is it the proper size? Is the relay kicking it in and out?

  8. #8
    Join Date
    Jul 2002
    Location
    Zelienople, Pa
    Posts
    2,965

    Re: Trane trouble

    Originally posted by bob burg
    Hooked up the gauge's.
    I hope you are EPA certified.
    How tall are you Private???!!!!

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