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Old 01-29-2012, 03:25 PM   #1
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40 VAC on refrigerator chassis to earth gnd


My house was built in 1963. Most outlets are two wire/two prong with no ground available. My refrigerator is about 3 months old.

I have over 25 years experience as an Electrical Engineering Technician working on Avionics. Aircraft wiring and house wiring is surprisingly different.

The outlet for my refrigerator is a three prong plug, but the ground, third, socket is open. The outlet box is metal, but open to ground.

I measured 40 VAC from the chassis of the fridge to earth ground, e.g. metal kitchen sink & also the copper water pipe input to the fridge for the ice maker.
Interestingly, the refrigerator side of the ice maker water input fitting is zero ohms to the fridge chassis. There is NO continuity from house side of the water input pipe and its fitting to the fridge side of that same fitting. There is Teflon tape on that fitting. That does not seem like it would be a 100% insulator (?). There is about 80 VAC from fridge chassis to AC-Hot.

I read on this forum that the proper fix for two to three prong outlets is to use a GFI outlet. I do not understand how that would solve my 40 volt fridge chassis problem. It would make it safer.

How do I solve this? Is GFI *and* a wire from fridge chassis to a clamp on the copper water input pipe the right answer?

Any help will be appreciated.

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Old 01-29-2012, 03:32 PM   #2
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40 VAC on refrigerator chassis to earth gnd


Sounds like the receptacle might be wired backwards.(Hot and neutral switched)

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Old 01-29-2012, 04:25 PM   #3
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40 VAC on refrigerator chassis to earth gnd


Had one of these a long time ago. The female HO felt a slight tingle when touching a grounded stove and the ungrounded fridge but others including me said they felt nothing.
The fridge worked fine, I assume moisture had somewhat compromised elec. insulation inside.

Assuming your neutral is grounded at the panel, one way to model this voltage or current source is to have a resistive leakage of '2 units' between the hot and the chassis and '1 unit' between the neutral and the chassis.

The 40v may not be dangerous if this equivalent leakage resistance voltage divider cannot supply more than 1 mA of current and a GFI won't trip if the leakage current is less than about 4 mA.
What was weird was that the leakage resistance changed depending on the current drawn. When I tried to calculate the equivalent resistance values I came out with negative numbers.

I'd find some way to ground the shell of the fridge. The current that this leakage resistance is capable of supplying may increase with time. When the grounded fridge starts tripping its breaker it's for sure time to go shopping.

Last edited by Yoyizit; 01-29-2012 at 04:31 PM.
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Old 01-29-2012, 04:58 PM   #4
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40 VAC on refrigerator chassis to earth gnd


Here we go again making calculations and creating a test bench instead of telling someone to get this fixed ASAP.

To Op, while this should not be normal that the refrigerator is shocking people, there is a problem in that the NEC requires the refrigerator to be used only on a grounded circuit.
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Old 01-29-2012, 05:15 PM   #5
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Old 01-29-2012, 05:16 PM   #6
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40 VAC on refrigerator chassis to earth gnd


Can you temp the fridge into a grounded extension cord to a grounded outlet?
Is the kitchen accessable from underneath where you could fish a new wire up to feed that plug,or maybe add a seperate grounded gfi for the fridge?
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Old 01-29-2012, 05:22 PM   #7
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40 VAC on refrigerator chassis to earth gnd


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Can you temp the fridge into a grounded extension cord to a grounded outlet?
Is the kitchen accessable from underneath where you could fish a new wire up to feed that plug,or maybe add a seperate grounded gfi for the fridge?
Better still run extension cord it to a GFCI outlet and see if the leakage current is enough to trip the GFCI. If so its time to retire this fridge.
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Old 01-29-2012, 05:32 PM   #8
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40 VAC on refrigerator chassis to earth gnd


A refrigerator 3 months old should still be under warranty.
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Old 01-29-2012, 05:42 PM   #9
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40 VAC on refrigerator chassis to earth gnd


Yeah three months old is not worth messing with. Just call the company about warranty. And hopefully fix the outlet.
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Old 01-29-2012, 07:11 PM   #10
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You know, if curiousB's GFCI trips, this goes beyond merely customer concerns or anxiety, and so you can almost certainly avoid any warranty hassles because this evidence raises product liability issues that not even the most hardened CEO can afford to ignore.
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Old 01-29-2012, 07:53 PM   #11
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40 VAC on refrigerator chassis to earth gnd


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I have over 25 years experience as an Electrical Engineering Technician working on Avionics. Aircraft wiring and house wiring is surprisingly different.
Well, here's the problem.
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Old 01-29-2012, 08:20 PM   #12
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40 VAC on refrigerator chassis to earth gnd


Is someone getting a shock from the fridge or is the reading perhaps one of those phantom voltages registered by a digital VOM?
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Old 01-29-2012, 08:52 PM   #13
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40 VAC on refrigerator chassis to earth gnd


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Is someone getting a shock from the fridge or is the reading perhaps one of those phantom voltages registered by a digital VOM?
Or is the mettallic water line energized?

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