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Compressor failure

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creger.robert
creger.robert Member Posts: 114
in A-C, Heat Pumps & Refrigeration

tempstar condenser R454b 3 months old

Compressor wont start

Windings ohm out c-r .6

C-s 1.1 c

R-s 1.6. Draws lra when try to start pops breaker 132 amps on start up try

228 volts at capacitor between common and hermetic

Wiring diagram shows optional start kit

Any thoughts?

Comments

  • HVACNUT
    HVACNUT Member Posts: 7,584

    Have you checked windings to ground?

    Windings are good. It definitely shouldn't be drawing locked rotor amps at 3 months.

    Was refrigerant added on top of the factory charge? If so, how much, and what's the line set length? Is the air handler above or below the condenser? When it did run, were pressures, SC and SH known? A new system that checks out ok electrically might be severely over charged.

  • creger.robert
    creger.robert Member Posts: 114

    i didnt put system in - was called out they had a power issue - brown out

    Electrician had to repair transfer switch on generator etc

    Windings to ground ok but compressor wont start

  • creger.robert
    creger.robert Member Posts: 114

    furnace is in basement- condenser on ground grade

    No idea on charge customer says worked fine for 3 months

  • pecmsg
    pecmsg Member Posts: 7,378
    edited July 27

    Were your reading when the pump was hot or cool?

    Get the exact ohm readings from the compressor manufactures website and compare to your readings.

    Ensure proper start components were installed.

    Check voltage at contactor and peckerhead.

  • HVACNUT
    HVACNUT Member Posts: 7,584
    edited July 27

    What's the LRA rating on the compressor?

    This is straight contactor and run capacitor? No circuit boards?

    I'd still be skeptical about the charge if all else checks out. Weigh it out.

  • ratio
    ratio Member Posts: 4,281

    What's the cap measure?

  • creger.robert
    creger.robert Member Posts: 114

    cap readings fine 79 mfd

    2228 volts c-hermetic

  • creger.robert
    creger.robert Member Posts: 114

    readings taken when cold

  • ChrisJ
    ChrisJ Member Posts: 17,583

    0.6 ohms.

    Is this compensating for lead resistance as well, or is that included in that?

    I'd use caution when using a typical multimeter to measure these resistances, especially something close to or less than 1 ohm. 0.6 ohms might very well be a dead short in this case.

    Single pipe 392sqft system with an EG-40 rated for 325sqft and it's silent and balanced at all times.

  • pecmsg
    pecmsg Member Posts: 7,378
    edited July 27

    How quickly does the breaker trip, instantly or after 3 - 8 seconds?

  • mattmia2
    mattmia2 Member Posts: 17,753

    need to know the current through the cap too.

    whatever took out the other stuff, i'm guessing not a "brownout" but primary voltage appearing on the secondary and the 4kv + caused a bunch of stuff to arc to ground. i would look at the compressor being shorted to ground.

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 20,711

    I would recheck all the wiring connections and the cap and the contactor from the breaker panel all the way out through the disconnect to the unit and the connections at the compressor.

    If you can't find anything, try a hard start kit as you will have nothing to lose at that point.

    Since you don't know the charge as you didn't install it you may want to pull the charge out (or at least some if it) to make sure the compressor isn't locked up.

    Some people think with refrigerant more is better.

    I had a 1 1/2 ton system with a piston and someone had installed a sight glass on it and filled it to the top. The suction and discharge were basically the same pressure when the compressor ran. Thought for sure the valves were busted (it was a recip) but all i had to do was take (a lot) of the charge out and it was fine it straightened right out.

  • mattmia2
    mattmia2 Member Posts: 17,753

    a manifold set will tell you if it is full of liquid. if the discharge pressure shoots up even maybe momentarily then the compressor is trying to pump liquid.

    i'm thinking the static pressure and temp will tell you something too but i'm not quite seeing how to look at it. there will be liquid and vapor but the vapor will be at the saturation pressure of he temp of the refrigerant.

  • HVACNUT
    HVACNUT Member Posts: 7,584

    If the compressor was checked at the compressor with the wires off, were the wires themselves checked? Maybe there's a pinch somewhere.

    mattmia2ChrisJ
  • mattmia2
    mattmia2 Member Posts: 17,753
    edited July 27

    it really should be tripping the overload, not the breaker if the compressor is failing to start. is the lra on the ratings plate around 130a?

    Did you check the resistance to ground? A ground fault in the compressor could trip the breaker instead of the overload depending on where the overload is in the ckt. You could try measuring the resistance to ground with a megger on the compressor with the circuit disconnected to see if there is a short that only shows up at line voltage.

    could also try a test overload and cap connected directly from the disconnect to the compressor to rule out other problems with the wiring and components.

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