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Old 10-09-2019, 11:26   #1
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Replacing generator run capacitor with aircons cap

I need to replace the capacitor on the generator with one that has a lower uf rating.

The one I have has two sets of terminals in top with no markings. The wires going to the terminals have no markings.

The only capacitors I can find here are dual capacitors for air conditioners that have three sets on terminals (fan, herm, com).

I know that I need to use herm and com but does it matter which wire goes to which terminal?
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Old 10-09-2019, 11:52   #2
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Re: Replacing generator run capacitor with aircons cap

No. The capacitors used as run capacitors for air conditioners are oil-filled and have no polarity. Similarly, the capacitors used for voltage control in generators are not polarized.


So you can connect the wires either way.
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Old 10-09-2019, 12:41   #3
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Re: Replacing generator run capacitor with aircons cap

I have found that a “genuine GE gentec capacitor” will way outlast a non branded one
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Old 12-09-2019, 00:14   #4
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Re: Replacing generator run capacitor with aircons cap

Capacitors are incredibly reliable over a very very very long service life....are you sure it needs replacing?
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Old 12-09-2019, 01:06   #5
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Re: Replacing generator run capacitor with aircons cap

Iv'e blown up a couple on my 240V 2.2kW genset using my inverter welder to crank the engine when I had flat batteries.
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Old 12-09-2019, 07:39   #6
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Re: Replacing generator run capacitor with aircons cap

Quote:
Originally Posted by Cowpoos View Post
Capacitors are incredibly reliable over a very very very long service life....are you sure it needs replacing?


They seem to go bad pretty frequently when used on generators, one likely plausible theory is heat. The location of mine is right in the intake airflow for the cooling air, not all generator manufacturers do so.
I had one go bad by changing its uf value, it showed up as slowly losing voltage, I replaced it with a cheap Chinese cap that just went out in 50 hours or less, I replaced that with a GE Gentec cap and it’s lasted for 500 hours? And maybe four years so far.

I’ve heard that the higher voltage rated caps are better/ last longer, but don’t know that, seems logical though.
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Old 12-09-2019, 08:07   #7
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Re: Replacing generator run capacitor with aircons cap

We don't even have a generator aboard but do have a couple of common run caps for generator voltage regulators because I've helped a number of folks replace them and in remote anchorages they can be hard to come by. From my experience seems to be a pretty common failure. For offshore ventures I actually recommend it as a necessary spare if the generator is anything close to lifestyle critical.

As noted above, no polarity, so leads can be connected as convenient. Also as noted, heat is the enemy, they can be remote mounted (within reason) and still perform their task.
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