Motor cap keeps blowing

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Thank you everyone for your thoughts on the situation I am having. Please remember that the 1st motor blew both caps. Start and Run. The second motor did the same thing. Replaced both caps and the start cap did not pop only the run cap. Voltage is good. I have no way of getting an amperage reading since the run cap blows as soon as the breaker is turned on. The motor does nothing, not even a hum. The breaker does not even trip.
Thanks again.
 
Blue Star Services LLC said:
Thank you everyone for your thoughts on the situation I am having. Please remember that the 1st motor blew both caps. Start and Run. The second motor did the same thing. Replaced both caps and the start cap did not pop only the run cap. Voltage is good. I have no way of getting an amperage reading since the run cap blows as soon as the breaker is turned on. The motor does nothing, not even a hum. The breaker does not even trip.
Thanks again.
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Remove the run cap. All it does is improve power factor when running. Then troubleshoot.
 
paulengr,
Would I have to put the 3 leads together going to the run cap for the motor to turn on or just leave them out of the loop? I was going to try this but was not sure if I would make more problems than I already have.
Thank You
 
Blue Star Services LLC said:
paulengr,
Would I have to put the 3 leads together going to the run cap for the motor to turn on or just leave them out of the loop? I was going to try this but was not sure if I would make more problems than I already have.
Thank You
Click to expand...

Helps if you know how it is wired.



Just disconnect it. It should still start and run
If the switch and start capacitor is good but it will run inefficiently. My suspicion is either you have a wiring issue or the starting switch is the issue which they often are.
 
paulengr said:
Helps if you know how it is wired.



Just disconnect it. It should still start and run
If the switch and start capacitor is good but it will run inefficiently. My suspicion is either you have a wiring issue or the starting switch is the issue which they often are.
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No it will not especially if the normal load is coupled to it, the links you provided even show it. The run capacitor is in series with the aux winding, you disconnect it and you have no circuit through the aux winding. No circuit through aux winding means you won't develop torque to turn the rotor. If the start caps and centrifugal switch are still good then those will work to get it started but it will run as a capacitor start induction run motor after that and won't have as much torque as originally designed.
 
kwired said:
No it will not especially if the normal load is coupled to it, the links you provided even show it. The run capacitor is in series with the aux winding, you disconnect it and you have no circuit through the aux winding. No circuit through aux winding means you won't develop torque to turn the rotor. If the start caps and centrifugal switch are still good then those will work to get it started but it will run as a capacitor start induction run motor after that and won't have as much torque as originally designed.
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The issue is the run cap keeps blowing. Sounds like either the potential relay/centrifugal switch is stuck open or start cap has failed so it should just buzz until the run cap blows up, which is the symptom. The run cap keeps blowing. So removing it should cause the motor to start running then stall if if everything is normal or not run if the start circuit branch is disabled without blowing out another capacitor. Lots of ways to troubleshoot this but the only moving part is the switch.
 
paulengr said:
The issue is the run cap keeps blowing. Sounds like either the potential relay/centrifugal switch is stuck open or start cap has failed so it should just buzz until the run cap blows up, which is the symptom. The run cap keeps blowing. So removing it should cause the motor to start running then stall if if everything is normal or not run if the start circuit branch is disabled without blowing out another capacitor. Lots of ways to troubleshoot this but the only moving part is the switch.
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I have fixed many stuck switches, relays, or blown start capacitors. Seldom does it take out the run capacitor as well. If the motor can develop enough torque to get rolling the run capacitor will accelerate to speed, just not as fast as with working start capacitors. Once up to speed you have same thing you normally have in the circuit. This could possibly lead to earlier failure of the run capacitor, but I doubt is what is going on with OP as he replaced original motor with a different one and is still having some problems.

If you do lose run capacitor but still have start capactitors and proper cut out of them - it will start somewhat normally but will have less than normal running torque.

We don't know if second motor lost capacitor immediately or if it took some time to develop. Immediately probably means defect or serious voltage issues.

Overloaded motor (mechanical failure, poor design, improper selection of motor/pump combination) maybe could be an issue but will likely take a little time to deteriorate to failure.
 
I'm going to throw something out there. Probably irrelevant but you never know. The fact that you mentioned three wires on the run cap is why. That and it is a different motor.

On some motors you will have only have one lead brought out for the run cap. You are expected to bring one of the line leads to the run cap. You have to bring the right phase.

On other motors two leads are brought out, typically brown and brown with white strip. On those you don't bring a phase wire to the cap.

Could it be there was a difference between the two motors and without knowing you now have A phase on one side of the cap and B phase on the other?
 
Ptonsparky, for me it is quite common on OEM condenser fan motors. Especially when they put the caps in the compartment with the contactors. And yes, the new replacement motors come with two leads for the caps, which confuses some of my guys.

Just thought it was worth a mention as a possibility. It is about the only way I can see a motor run cap blow the second the motor is energized.
 
Russs57 said:
Ptonsparky, for me it is quite common on OEM condenser fan motors. Especially when they put the caps in the compartment with the contactors. And yes, the new replacement motors come with two leads for the caps, which confuses some of my guys.

Just thought it was worth a mention as a possibility. It is about the only way I can see a motor run cap blow the second the motor is energized.
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I had forgotten those and similar. :rolleyes:
 
Russs57 said:
Ptonsparky, for me it is quite common on OEM condenser fan motors. Especially when they put the caps in the compartment with the contactors. And yes, the new replacement motors come with two leads for the caps, which confuses some of my guys.

Just thought it was worth a mention as a possibility. It is about the only way I can see a motor run cap blow the second the motor is energized.
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That is about only place I run into this is with OEM motors particularly on HVAC equipment.

The replacement motors will have two leads for the caps, if motor is same design one of those leads is internally connected to one of the incoming power leads and you essentially have the same thing anyway.

There may be other definite purpose motors out there that are similar. I do run into this at times with crop drying fan motors as well.

General purpose motors the capacitors are already factory installed and connected and all you connect is the main supply leads when installing the motor.
 
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