Standby generator capacitors

Joined
Sep 26, 2004
Messages
313
Location
South La
I had a problem with a B/S 12k standby gen right after a hurricane. It would start up but only run for about 3 or so seconds .Today I jump the sol to
keep it running long enough to take some readings. Readings at 180 volts instead of 240 but the hz was at 61. This told me the engine was running to speed but something was going on with the generator end. It had two capacitors and one was busted. Question is could you get by with a motor running capacitor with the same rating or do you need one made for a generator? You can see the grey matter instead of oil in this capacitor.

20211115_123004.jpg
 
Joined
Aug 28, 2017
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near Cincinnati, OH
The manufacturer probably considers it a motor capacitor. You can "get by" with any having suitable voltage and uF rating but that is a (polypropylene, most likely) film capacitor that should have self healing and higher temperature tolerance for longer life. So, I'd get a motor cap that's polyprop. and only use a wet electrolytic if it's an emergency just to make power for the time being.
 
Joined
Jan 3, 2006
Messages
1,786
Location
Ohio
Bulging cap means it's done. A capacitor for motor operation (HVAC for example) would be fine, just make sure it meets the capacitance and at least the same voltage rating.
 
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Sep 26, 2017
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1,437
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Under the Hood
I check my Furnace Capacitor yearly and will change it if it goes out of tolerance (or looks doomed).

I think everybody on this site should know how to check one.
There in any machine with an 'electric' motor.
You just need a multi-Meter that can measure Micro Fareds.
 
Last edited:

passgas55

Thread starter
Joined
Sep 26, 2004
Messages
313
Location
South La
I had a fluke 11 that did check capacitors. Just make sure you have a multi meter that has enough range for motor capacitors. Some of the meters are just enough range for electronic capacitors. I need to get another one.
 
Joined
Jul 10, 2009
Messages
60
Location
IL
I had a tech come to my house for a refrigerant leak and he showed me a dead mouse that he said had died shorting out the motor capacitor on the outdoor unit. He showed me the Fluke meter, which popped up and dropped to zero, which he said indicated a dead cap. I asked him to show me the meter, which was set to resistance. Asked him to set it to measure capacitance, which was spot on, so I asked him to take his mouse and leave.
 
Joined
Jan 14, 2015
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Location
missouri
that meter checks at a volt or 2. The cap works at 280 peak. I no longer need to run the ac while I am at work, so I just go buy a spare and have it handy if the unit does not start. It seems if you have a spare, they never fail.
 
Joined
Sep 29, 2009
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3,005
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Deep in the heart of Jersey
I doub't any device that requires a cap, knows or cares what that cap was designed to be used in. As long as the numbers on the original cap are the same, or a little higher as the one it came with, it will work fine.,,
 
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