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Help Airconditioner Condensor unit Problem

Discussion in 'Electrical Engineering' started by **THE-RFI-EMI-GUY**, Feb 5, 2005.

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  1. My wife called me from the house. She is in Orlando and there is a cold
    wave so the heat pump cycle is turned on.

    Here is the problem:

    1) Power went out yesterday. She found main 150A disconnect outside popped;

    2) Power went out this morning, same problem. She did note that the
    lights "blinked" a couple times before the episode. She also thinks she
    heard the heat pump come on.

    I had her feel each of the breakers for warmth, the 150A main disconnect
    is outside and it (as well as ambient) was cold. She noted some warmth
    from the breakers for the HVAC system which seems normal to me.

    3) This evening she was outside and heard a noise from the heat pump
    (outdoor unit, ~ 4 ton Trane) and observed dark smoke eminating from it.
    This time the main 150A disconnect did not trip.

    At this point I had her turn off the breakers for the HVAC. The only
    other potential loads are a pair of pool pumps.

    My questions:

    1) Why would the 150 Amp breaker trip out without the much smaller
    distribution breakers going first?
    2) Could a shorted motor start capacitor cause this type of failure
    sequence?
    3) Any thoughts of possible failure modes within the Condensor unit
    which would cause such a failure?



    --
    Joe Leikhim K4SAT
    "The RFI-EMI-GUY"

    The Lost Deep Thoughts By: Jack Handey
    Before a mad scientist goes mad, there's probably a time
    when he's only partially mad. And this is the time when he's
    going to throw his best parties.
     
  2. Guest

    Here's a possible explanation for question 1)
    The 150 amp main is feeding all the circuits and
    is carrying X amps prior to the fault. The fault
    occurs, drawing Y amps from the motor start rated
    breaker for its circuit. That breaker will delay
    before tripping. But the X + Y amps exceeds 150
    and trips the 150 amp main.

    Question 2): yes. Question 3) don't know.

    Ed
     
  3. Thanks I though that as well as there are the pool pump loads to
    consider as well.


    --
    Joe Leikhim K4SAT
    "The RFI-EMI-GUY"

    The Lost Deep Thoughts By: Jack Handey
    Before a mad scientist goes mad, there's probably a time
    when he's only partially mad. And this is the time when he's
    going to throw his best parties.
     
  4. SQLit

    SQLit Guest

    snipped

    not at all if the current load excedes the setting the breaker trips.
    I have seen 3000 amp mains trip because of non-existant coordination with
    the breakers.
    After all the main is the first breaker feeding the a/c
    Not all at all the main will trip phase to phase or phase to ground.
    breakers for residences are not all that complicated. Most are just thermal
    and over load.

    In the old days before, el cheapo, fuses were place near the unit in the
    disconnect. Now days the disconnects are not fused. Personally I like the
    idea of opening some fuses before the main opens. My home circa 1999 does
    not have fused disconnect.


    snipped again

    I was quoted $5400.00 to replace a split system in my home this summer. 3
    ton Trane, with vfd air handler. My system is in running condition.
    Replacing the piping to the a/h is necessary in some situations, burn out of
    the compressor. Have the oil tested to be sure. If burnt replace.
     
  5. Roy Q.T.

    Roy Q.T. Guest

    I think it is obvious you have the correct load on your branch circuit
    breakers ~[supplying your heater] but your total load [from all your On
    circuits] exceeds the Amperage of your Main or Master Circuit Beaker ~
    or on just one of it's legs. (since they are tied together it'll trip
    both breakers with just one Branch Overloaded ~>

    check the individual load on each leg of your 3P/240 Service, (then
    check which individual load is highest & lowest on each circuit breaker)
    with everything On as when the trip occured, [Jot Them Down] and see if
    you can balance the loads between them, (one may be pulling more than
    the other) switch circuits off one side to the other to obtain a
    Balanced Load your Main Circuit Breakers can handle in harmony.

    use your ammeter & Do the math from your measurements and just transfer
    enough of the loads around to get it under your Mains seperate Ampacity.


    * If they are both maxed out; check your Service to Panel wire sizes and
    upgrade your Main Circuit Breaker to 200 A if it falls within their
    Tolerance.It doesn't sound like a big problem to me, Hopefully: just a
    matter of Balancing your Branch Circuit Loads as close as possible &
    under your Circuit Breakers Capacity.

    Example: let's say you have a draw of 152A on the one leg that tripped
    and 125A on the other; there is usually a circuit you can interchange
    off the 152A load with one or two from the 125A load side.....Good Luck
     
  6. Roy Q.T.

    Roy Q.T. Guest

    I almost forgot: your heat pump displayed some smoke and that could mean
    a bad unit that will require seperate attention.

    It is possible that an unbalanced overloaded distribution panel was not
    letting sufficient current to it lowering it's ampacity or draw and it
    browned out after the first symptomatic trip, thus not causing a trip
    the second time.
     
  7. Thanks all. I will deliver a postmortem when I get back into town.

    --
    Joe Leikhim K4SAT
    "The RFI-EMI-GUY"

    The Lost Deep Thoughts By: Jack Handey
    Before a mad scientist goes mad, there's probably a time
    when he's only partially mad. And this is the time when he's
    going to throw his best parties.
     
  8. Phil;
    This heat pump unit turns out to be a Bryant 697C with an FK4 air
    handler. It was installed in 1997 and therfore has time left on the 10
    year factory "limited" warranty for the compressor.

    Assuming that Bryant honors the warranty, what would be involved in
    cleansing the remainder of the system of contaminated freon and oil? Are
    there solutions to neutralize the PH of the system?

    How is Bryant to deal with for a scroll compressor factory warranty? Any
    qualifications? Have you seen their warranty in print anywhere? I am
    second owner.

    I should mention that I am on a budget at the moment as other work needs
    to be done including a roof!

    By the way there are two pool pumps which share the 150 A service
    disconnect breaker via another distribution panel, so during the
    tripping events, some additional load may have been present to trip that
    breaker.

    Joe Leikhim

    --
    Joe Leikhim K4SAT
    "The RFI-EMI-GUY"

    The Lost Deep Thoughts By: Jack Handey
    Before a mad scientist goes mad, there's probably a time
    when he's only partially mad. And this is the time when he's
    going to throw his best parties.
     
  9. Thanks for the help Phil; I would like to salvage the system if at all
    possible. The original owners paid $4500 for the system and it looked to
    be in fine condition when the house was inspected just a few weeks ago.
    Just bad luck on my part that it went out 3 days after the closing.

    By the way, if the system has to be opened up, I was wondering if there
    is a way to tandem in a small air handler for the garage alone? This
    house is laid out such that a wall shaker won't look good for the garage
    and I don't want house and garage air conditioning to mix. Is such a
    thing possible? Two air handlers from one compressor?


    --
    Joe Leikhim K4SAT
    "The RFI-EMI-GUY"

    The Lost Deep Thoughts By: Jack Handey
    Before a mad scientist goes mad, there's probably a time
    when he's only partially mad. And this is the time when he's
    going to throw his best parties.
     
  10. Thanks Phil; I will try another solution for the garage, don't want to
    risk the main system.

    --
    Joe Leikhim K4SAT
    "The RFI-EMI-GUY"

    The Lost Deep Thoughts By: Jack Handey
    Before a mad scientist goes mad, there's probably a time
    when he's only partially mad. And this is the time when he's
    going to throw his best parties.
     
  11. Guest

    Just a consumer comment - I have no AC expertise:
    The Mitsubishi split unit is GREAT. We just had one installed last summer,
    and man, does it ever work well! The price will make you choke, but
    the performance is like heaven.

    Ed
     
  12. Guest

    I don't know - I have no basis for comparison. FWIW Here's
    how mine was done: drill a hole (3" diameter, I think) through
    the wall; run tubing/drain/wiring through it to the inside unit.
    Outside, everything runs down the wall inside a downspout.
    The tube runs to the outside unit inside foam insullation. You
    cut it and flare the end and connect. Wiring runs in Carflex.

    What impressed me the most is that this unit just plain does
    not care what the environment presents. It cools/drys the
    air to the temp you set - even below 60 degrees. And it
    never freezes up as the window A/C's sometimes did.
    Damn thing is so quiet I can't hear if its on, but the LED
    indicator lets you know. The TV style remote control is a
    hoot! Who woulda thought you'd ever remote control an A/C
    with one?

    Ed
     
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