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Old 09-05-2010, 01:03 PM   #1
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What wires to a condenser unit


My GE BWR724A100A1 condenser unit of my heat pump is not working. The voltage at one pole is about 120 V, but on the other pole is about 10 V!. The AC person said I should have 120 on the other pole as well. Inside the house all the breakers are ON.

Should the low voltage of the thermostat come to the condenser unit at all?

Any suggestion how to proceed trouble shooting this?

Thanks.

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Old 09-05-2010, 02:40 PM   #2
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What wires to a condenser unit


See if there's a fuse in the electrical disconnect outside. If not turn the AC breaker off then back on. Need to fix whatever isn't letting the second leg through.

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Old 09-05-2010, 02:41 PM   #3
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What wires to a condenser unit


Almost sounds like the tech didn't know how to measure voltage properly.

The contactor will have line voltage and low voltage going to it. Line voltage 24/7, and low voltage only when the thermostat is calling for heat or cooling.

GE was bought by Trane in 83, so you have a very old unit. Might want to get your own voltage meter out, and start checking for what does, and what doesn't have proper voltage. Could be a bad breaker.
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Old 09-05-2010, 03:01 PM   #4
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What wires to a condenser unit


Thank you Beenthere. I measured the voltage on one pole and it was about 120 V. The other pole of the contactor (outside) has the same wire thickness as the first pole. I assume it should receive 120V so that the unit gets 240 V. Whould I look for low voltage also? What voltage shoujld be coming to the condenser? Does the thermostat directly control the condenser?

Thanks.
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Old 09-05-2010, 03:16 PM   #5
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What wires to a condenser unit


You should measure across both poles of the contactor to see if you have 240 volts. Measuring just one pole to ground, isn't what you do.

You should have some thinner wires going to the contactor, that come from the air handler/thermostat. They should go to the contactors coil, and measure 24 or so volts if the thermostat is calling for cooling.

You probably have a tripped or bad breaker/blown fuse.
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Old 09-06-2010, 07:51 AM   #6
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What wires to a condenser unit


Thanks Beenthere. I am not sure what breaker inside the house I flipped so that I got 240V between the two poles of the contactor ouside. The contactor has only two fuses, there is no coil. I noticed a low voltage wire going to the body of the condenser.

With the 240 V coming to the condenser, I put the thermost to call for calling. I heard a hum for about 4 sec., then everything is dead. The fan did not attempt to come on. I measured the voltages after this:
between one pole and ground: 120 V
Between the other pole and ground: 10V
between the two poles 110 V.

Coluld it be a stuck compressor?

Thanks
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Old 09-06-2010, 07:56 AM   #7
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What wires to a condenser unit


Yes it could be. or even a short in the compressor.

Your contactor has a coil, or it wouldn't pull in when the thermostat calls for cooling. Yours may be enclosed that you don't see it, but it is there. Its not the cause of the problem though.
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Old 09-06-2010, 09:26 AM   #8
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What wires to a condenser unit


What beenthere said. Sounds like maybe a case ground compressor. If you take the wires off of the compressor terminals, you can set your meter to ohms and check for continuity from the terminals to the case of the compressor. If you get continuity then your compressor is done.
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Old 09-10-2010, 11:29 AM   #9
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What wires to a condenser unit


Sound like your capacitor might be blown. Does your unit make a hum when it's trying to start up? If I'd does have a look in the electrical housing of your condensing unit an find a round or oval cylinder. If your meter reads micro farads test between the c and herm terminals and see if if matches to the rating plate on the cap.
If your meter doesn't read farads then visually inspect the cap, if it rounded on top and bottom then your cap is probably the issue.
Good luck... Replacing a cap is ALOT less expensive then replacing a compressor.
Remember there is a lot of voltage stored in capacitors so turn off power and don't test the cap with the wires attached.

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