AboutCraig HVAC Expert Expertise I have been in the HVAC field for the past 12+ years. I can help with most HVAC questions. I work on commerical buildings for the most part, and have yet to find anything I could not troubleshoot and repair, when repairable. I work on small 1 ton units to a 2500 ton chiller. Troubleshoot air flow, elect, and control problems. I attend regular classes to keep up with the latest and greatest.
Experience I have work in the HVAC trade for the past sixteen years. I work on commerical sites, hospitals, gov't buildings. I can troubleshoot just about anything in the HVAC business.
Education/Credentials 5 years union trade school, VFD training classes, Liebert factory training, some York and Trane factory training.
Question QUESTION: Craig, here's the scenario.
I have a 32 year old central air unit. Last year the bearings in the fan went bad. I bought a new 1/3 hp closed air/over motor with the recommended 10 Mfd cap & a new recommended fan prop as well. ( from Graingers)
The new motor overheats and trips the thermal.
The run cap checks at about 9mfd (2654*A)/V
My line voltage is 242V
the motor is drawing 2.1A, rated 2.3-2.4 . I de-pitched the fan to reduce the amp draw but the motor still overheated.
I have jumped across the contactor to bring the power directly from the line to the motor ( to eliminate the contactor)
I have wired the motor with one lead going across the cap and insulating the brown/white wire. Same result.
I even exchanged the motor for a new one, with the exact same results!
Thanks,
Ned Sweeney
ANSWER: The heat coming out of the cond unit could cause the motor to overheat. If the fan is not spinning in the proper direction or not wired properly will also cause it to overheat. With only one wire attached to the run cap WILL cause the motor to fail. As I can not see how you have things wired, my guess is you have something wired wrong.
Craig
achelpguy@gmail.com
---------- FOLLOW-UP ----------
QUESTION: Craig,
At this point I do not have the condenser running. I have the motor wired directly into the 220V line with the condenser leads pulled off of the contactor.
The motor has a purple, a black, a brown, & a brown/white lead. The motor has two options for wiring.
The first is with the brown & brown/white leads to the run cap, & the purple & black to the 220V. That's how it is now.
I also tried the optional wiring with the purple to the one side of the cap then continuing on to one side of the 220V. In this case the brown wire goes to the other side of the cap & the brown/white wire is insulated. The black wire is tied off to the other side of the 220V. I tried this as well with the same overheating problem.
Thanks for your continued help!
Answer With the motor not pulling FLA, it is odd that it is overheating. From you description, the wiring sounds correct. You can try and adjust the height of the prop on the shaft to see if you can get the amps down a bit. That might help the motor run cooler. I have seen cases where a lot (production run) of motors or pumps come bad. We had to change the motor from the factory six times and they realized the lot was bad and not up to spec. Since you bought both motors from the same place, that might be the problem. You should also consider checking the voltage to see if there is a drop when the motor is running. You might even consider getting another motor from another store, to see if it works. If it works, then take the one back and ask for a refund.
