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54067323

join:2012-09-25
Tuscaloosa, AL
reply to tp0d

Re: The GFI for the refrigerator tripped

said by tp0d:

I meant the chance of water causing a partial short to ground or chassis is pretty damn rare in a ressy setting.

I guess it depends upon the conditions the fridge is working in, close to the shore or with a prevailing wind off the ocean will bring moisture and in some cases salt air.

Much more of a chance for the windings in the compressor to overheat and cause the failure of the insulation, which I have seen in fridges and a few washing machines.

Overheating of the windings, commonly the result of failing to keep the condenser clean is a cancer to the insulation of the windings which are quite thin, it begins with a little bit of resistance to the grounded frame the wiring is wrapped around.

At this point it can trip a GFCI.

But most fridges are not connected thru a GFCI and what happens then is the already overloaded compressor has now picked up the burden of the failing wiring overheating it even more causing more insulation damage and sooner or later there is a flashover and that’s the end of the compressor.

And that’s a hard fault and easy to shoot.


shdesigns
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reply to 54067323
said by 54067323:

Revelant is comparing a "Our company makes a commercial/industrial bench top polisher/grinder which uses a water supply, so our customers want to use a GFCI. It runs on 115VAC single phase which powers a motor speed controller (frequency drive), which drives a 1hp 3 phase 230VAC motor. When the motor runs, the GFCI will trip almost instantly." to a residential refrigerator?

You have to be kidding.

My VFD running the 220V 3-phase motor on my lathe will trip the GFCI instantly.

It says why in the VFD manual. I used a generic motor. The manual states a non VFD-certified motor will have too much capacitance for the high-frequency pulses generated by the VFD and cause leakage currents.

Even with a VFD-rated motor it may need a reactor to reduce the stray currents.

BTW, my VFD runs at 8khz PWM.

This has nothing to do with a fridge

Sounds like this polisher/grinder took some shortcuts.
--
Scott Henion

Embedded Systems Consultant,
SHDesigns home - DIY Welder

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1

2 edits
said by shdesigns:

This has nothing to do with a fridge

The UK IET link I posted earlier has the title "Fridge Freezer tripping RCD" ... residual current device being the proper term for GFCI/GFI.
»www.theiet.org/forums/forum/mess···id=34284

*** another relevant link: »www.google.com/patents/US8011198
A/C compressor, not fridge, but address transient leakage tripping GFCI. Effects of the Invention Even if the motor is immersed in the lubricating oil, the leakage current is reduced, and the occurrence of a trouble such that the earth leakage breaker malfunctions is suppressed.

said by shdesigns:

Sounds like this polisher/grinder took some shortcuts.

The "relevant" issue highlighted in those links is the inability of typical GFCI to distinguish between steady 60Hz leakage current (dangerous to humans) and transient higher frequency leakage current (usually not dangerous to humans, but may trip GFCI).

The polisher/grinder guy actually measured the steady leakage current (2mA) and correctly assumed GFCI was tripping because of high frequency noise. He probably did not have the equipment to measure transient leakage current.

I have measured quite a few fridges, old and new, compressor on and off, on dry vs humid days. Typical GFCI trips between 4mA-6mA while the transients peak between 5mA-10mA. It is not a good match.

Since Leviton (and probably other companies) have started selling newer design GFCI which are less sensitive to transient leakage current, there is no reason to stay with older design GFCI for fridge, microwave and other troublesome appliances.


54067323

join:2012-09-25
Tuscaloosa, AL
said by lutful:

*** another relevant link: »www.google.com/patents/US8011198

Which still has nothing to do with the compressor in a residential refrigerator.

lutful
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join:2005-06-16
Ottawa, ON
kudos:1

1 edit
reply to grobinette
Click for full size
said by grobinette:

Some of you guys spend an awful lot of time arguing how much you know and waste an equal amount of time going off topic and not answering questions. Take a break.

IMHO ... just one forum member needs to take a break from reading my posts.

OP has described nuisance tripping when the compressor is turning on. I provided an educated guess that it is probably due to high frequency noise and would not have tried to explain it further if my original opinion was not ridiculed.

Anyway, there is no downside to using the new HF noise immune GFCI.


whizkid3
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join:2002-02-21
Queens, NY
kudos:9
reply to xpen
My recommendation is that the OP should have the refrigerator serviced or replaced, so that the situation is no longer an issue. A fridge that trips a GFCI could be a dangerous shock hazard. Its an appliance. They get old and fail.

Once that is done; my recommendation is to replace the receptacle (or re-wire the circuit) so the fridge is no longer on GFCI. There is no code requirement for this. I personally don't see the need to have everything in the home on GFCI just so one could avoid any type of shock hazard. If it were such a prominent risk, the electric code would likely require it.