Question about AO Smith 2 Hp Spl 3450rpm M56 Frame 115/230 Volts Replacement Air Compressor Motor Electric Motor No.B381
Our 2 HP Speedaire horizontal tank compressor is rated 115 / 230 volts at 24 / 12 amps, respectively. This means at 115 volts, a 30 amp circuit breaker is the bare minimum. That also means that the wiring should be #10 copper wires for short runs, but the next size up; #8 copper wires would be better connected to a 40 amp circuit breaker. Running at 230 drops the amperage requirement by half, to 12. A #14 copper wire is minimum for short runs with a double pole 15 amp circuit breaker, but #12 copper wires connected to a double pole 20 amp circuit breaker would be better choice.
If the compressor is cord connected (or even directly wired) with the minimum sized wires, it will likely a voltage drop problem unless very close to the panel. This problem is more pronounced as the distance between the circuit breaker and motor increases, or when smaller wires are in the circuit. All the voltage at the circuit breaker does not reach the motor, as it is lost as heat; so the compressor only sees 90 to 105 volts instead of the 115 volts it expects.
If the cords, connections, etc are getting hot, it is a tell tale sign of under-sized wires and /or poor connections. Once you solve these problems, the compressor should run "as advertised " because motors usually don't "go bad" but fail all at once. Unless you have a bearing problem - or there is a problem with the load itself (compressor).
I hope this helped.
Posted on Nov 12, 2009
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Posted on Jan 02, 2017
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