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Electric Motors/Compressor motor


I have an old sears air compressor with a 1hp GE motor & 12g tank. Always worked fine, I have it plugged in on its own 20amp circuit breaker alone, direct with no extension cord, one day i went to turn it on and it just made a clicking noise, so i left it for a while then tried it again now it runs for about 20 seconds then it shuts off because it trips the breaker.  does this sound like one of the capacitors is bad (it has 2)? If so witch one? Or does the whole motor need to be rebuilt?

About the largest motor that will start on a 15 amp 120 residential system is 1/2 HP

NEMA rates a 1HP 115/120 volt at 16 amps  it might be the motor is too much for the circuit

Not sure about the clicking noise,  is it still there ?

20 seconds should get it out of locked rotor  which can pull from 4 to 10 times full load,  so it could be creating a voltage drop,  and the breaker is just not taking the load from start,  

I would have it tested on a larger system say a 50 amp system where they can get the running current no load,   right there should tell if you the 20 amp breaker is going to hold it,

16 amps NEMA is average  so this one might pull 20 amps depending on the ACTUAL VOLTAGE at the motor,   

The clicking sound sounds like it was trying to trip the centrifugal switch and then falling below before it dropped the start circuit,  so you have multiple caps are both metal cans or one plastic and one metal ?  Or two plastic?

One of each is a cap start cap run,  two plastic is probably a cap start with two caps wired in parallel.   and if any of them on the top  has a round hole  and that round area is pushed out of puffed up   the cap is bad,   if one is bad  replace all

No load or belts on the motor right?

Make sure you get it running with nothing on it first   1HP is tough in a residential circuit,  

If it is dual voltage  and it can be ran on 220 that might help with the wire size  for a new circuit  

But I would get it tested on a test circuit so you know what the running current is  and then measure the voltage at the outlet  and make sure if you have 114 or 121 volts   utilties are not consistent   even though they swear they never made a bad volt ever   mine runs from 116 to 119 and even lower      depending on day time of year  time of day so on,   

a few volts can bring the motor over the knee of the curve and that is that   

There is not a good way to soft start a single phase cap motor,  the low voltage is not a help

Now if it is on the compressor with a belt   it could be the load of compressed air  is too much to overcome PAST the start current   then you would need some kind of unloader on the compressor to cure that  

Find out what the exact voltage is at the outlet   then find out what the running current is no load   from there we can figure out what way to attack this problem  

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Three phase/ AC DC single phase motors, controls, any problems or failures, motor installation, performance issues, connections. All other electric motors/gearboxes/apparatus. Specialty repair concerns, obsolete motors and solutions. Other mechanical or specialty equipment. See my profile under Home/electrical at this site


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