Finding source of a ground fault in an appliance


Old 04-14-11, 01:09 PM
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Finding source of a ground fault in an appliance

I have an autoclave that trips a GFI when switched on, but operates normally when plugged into a standard outlet. I find no stray voltage from its cabinet to a water pipe under the latter condition. The problem started showing up some years ago when sloppy filling spilled water into the cabinet or when excessive steam was vented, but then it would function normally once it dried out. I'm hoping there is some kind of algorithm that could be followed to trace the cause of this momentary grounding. Using an ohm meter, should it be set to detect a direct short, or should it be set to the highest resistance setting to search for trace conduction through heavy resistance?
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Old 04-14-11, 03:20 PM
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A standard ground fault will trip between 4 -6 milliamps which is .004 - .006 amps. Of course you don't really know if it is 6 MA or 600MA the GFCI still trips. Maybe a better way is to disconnect all the components of the maching, and then reconnect (with the power off) them until the GFCI trips. Then you know your bad part.

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