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having problems with a compressor contactor fusing together evert 2 weeks. no voltage drop across contact poin
a new compressor replacement occured a few weeks ago and every two weeks the contactor fuses together on 2 of the three leggs causing the compressor to shut down on internal overloads.
208/230 vot 3 phase power. each leg read 120 to 124 volts to ground.no voltage drop on contact point from line to load. 40 amp contactor with compressor running at about 12 to 13 amps per leg. watched it cycle on and off. everytime threr unable to find anything wrong. copeland requirements is max of 30degrees super heat at compressor or less. getting about 28 degrees. this is second compessor in 2 months. its like clock work every 12 to 14 days contactor melts together.
Could there be a voltage drop to the main panel from power grid at night causing higer amp draw. all wire connections are tight back to & including the breaker. a/c unit is in the same panel and it is only happening to the walkin cooler condenser
A contactor used to control a motor should be (must be per code) rated in horsepower, not amps. A contactor rated in amps may not be designed to handle the motor starting current or to break the motor current under overload conditions.
A voltage drop could cause the motor to overload and even stall. If this happens at a specific time of day, the voltage drop might be due to daily distribution system load fluctuations. There might also be a problem with several large motors starting at the same time. The other motors might be in your facility or in a neighboring facility.
I am suggesting a problem with the contactor plus an electrical or mechanical problem with starting or operating the motor.
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