Condenser fan seems to be overheating

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Old 09-03-08, 05:23 PM
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Condenser fan seems to be overheating

The other day the condenser fan motor on my home A/C unit failed. It's a 1/4 horse 230 volt motor, it mounts in the grill at the top of the unit, hangs shaft down and pulls air up through the coils past the motor and out the top of the unit. The old motor has 3 wires (black, blue and orange) and is on a double capacitor. I went to the local appliance supply store and they had a 1/3 hp motor they told me would work fine. A local A/C repair guy who was waiting in line confirmed that and gave me a primer on how to wire it since it had 4 wires (white, black, brown and brown with white stripe)instead of 3. I walked out with the motor and a 12.5 mf 370 volt run capacitor, which is what is specified on the motor plate.

The old motor had a skeletonized end plate on the shaft end, the new one is solid. I put the fan as close to the body of the motor as possible, which was how it was mounted on the old one.

After mounting it I wired it as he told me to, with the new black wire going to where the old black wire was, on the contactor, and the new white wire going to where the old orange wire went, which was on a the old double capacitor, but on a terminal that also had a jumper wire going to the contactor side opposite of the black wire. I just connected white to where that jumper goes. I read 238 volts across those points. The motor plate calls for 208-230. I connected the brown and brown/white strip wires to the new run capacitor, which is what the diagram on the motor calls for.

I turned it on and fired up and worked fine. 1 hour later it shut itself down, the motor was very hot but still turned freely, my infrared thermometer read 228 degrees on the motor housing (it's 105 out today). I rechecked my wiring and called the A/C guy I talked to at the store. He confirmed my wiring was correct and said I probably got a bad run capacitor, to go buy another one. I did, came home today and hooked it up. It ran for an hour and the fan stopped and again the temp is 228 at the motor housing. As soon as it cools it will start and run till the 230 degree point, where it shuts down again.

The fan blades are rotating in the correct direction. The capacitor is the correct one as called for on the motor label. It's a GE motor and says it's a condenser fan motor on the box. The max amp draw as stated on the motor is 2.4 amps and it's drawing 2.1.

Why is it overheating and shutting down? Can it be the solid end plate on the motor housing? I can see that the fan could have blown a lot of air into the old motor to cool it, but that's not possible with the new motor.

Heck, it's only 105 today, what am I going to do next summer when it really gets hot out?
 

Last edited by 3rdpig; 09-03-08 at 06:17 PM.
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  #2  
Old 09-05-08, 01:14 PM
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Location: Phoenix
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No, you really should have a TEAO (totally enclosed air over) motor on an outside condenser unit. Something is strange about your temp measurement. You're measuring 108 deg C on the housing which would indicate a somewhat higher temp inside. The motor is supposed to kick out at 60 deg C.

Did you completely eliminate the connections between the new motor and the old capacitor? I'm wondering if you now have both capacitors in the fan motor circuit?
 
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