AboutJim Barnhart Expertise Fifty + years in Heating, Ventilating, Air Conditioning, Sheet Metal Manufacturing.
Semi retired since 1995,
Experience Answer questions about , residential and commercial.
Answer questions about sheet metal fabrication.
Fifty years plus experience.
No answers for oil equipment, No answers for kitchen appliances, No answers for laundry appliances.
Question QUESTION: Jim, 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 its internal 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!
ANSWER: Ned,
I have no idea?
If the motor is drawing less amps, the line voltage is satasfactory, I don't know what bypassing the contactor dose.
I assume the unit covers are in place?
---------- FOLLOW-UP ----------
QUESTION: Jim,
The unit is a hinged lid unit with the fan in the lid. I've tried it with the lid open and closed, with the condensor running and the condenser not running.
The alternate wiring I did through the cap with one of the 220V leads is an optional wiring schematic that is on the side of the motor. It still overheated. It takes about 75 minutes to overheat. Maybe it shouldn't run for 75 minutes straight but it is an old unit on an old house. On hot days it can run almost continuously.
Thanks for your help.
Answer Ned,
The more air a fan motor pushes the warmer it will run and the more amps it will draw.
If you had a fan running in a closed box with no openings it would run cooler and with less amp draw, if you opened a side, one, two or three each time it would run a little warmer and draw more amps.
Same thing might apply if the fan blows through a grill it would run warmer, draw more amps if the grill were removed.
