Microwave to stove 63 volts

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captstent

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I have a 66 year old house. The microwave is plugged into a GFCI with no ground. The electric stove next to it is 240 volt.
Is there not being a ground in the outlet the microwave is plugged into the reason for the shock and why isn't the GFCI not tripping.
You get a good tingle when you touch the metal exterior of the microwave and the non enameled handle on the stove but also to a
lesser degree if you touch the enameled part of the stove. Touching the stove by itself isn't a problem. Touching the microwave by
itself is no problem. Touching both is the 63 volt problem. Any ideas?
 
If I’m reading this correctly, it sounds like you have a ground fault in one of the appliances.

Because the cases are not grounded, the GFCI does not trip. When you touch both, you complete the circuit, but none of the current is going to ground, it’s returning in the neutral, so again, the GFCI does not trip.

In my opinion, my theory would only be correct if this is an older stove with the neutral bonded to the case.
 
Finding which appliance or circuit has the fault is relatively easy, turn off the breaker to the microwave, voltage disappears? Fault is in the microwave. Doesn’t disappear? Turn off the stove. Still doesn’t disappear? Start turning off and on ever breaker in the panel until the voltage disappears. That will give you a starting point on where to look.
 
The measured 63V might be due to a powerline filter inside of the microwave that's used to reduce conducted EMI coming from a switching supply providing high voltage to the magnetron. Such a filter likely includes a capacitor between line and case ground, and also between neutral and case ground. That could act as a capacitive voltage divider causing about 120V /2 = 60V to appear from the case of the microwave to the equipment ground of the electrical system when the case is not grounded.
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The 1283 UL standard allows up to 0.5mA of leakage current from EMI filters in cord connected appliances. But some people can perceive as little as 0.25mA with a tingling sensation, which is much less than the nominal 5mA trip point of a GFCI.
 
ptonsparky said:
GFCIs with no EG rely on you as the path to earth. It will hurt when it trips.

You need to determine which item is the problem. Use an extension cord to a receptacle with a known good EG. Get your meter out and do some tests.
Click to expand...
I like the test. I'll let you know what I find
 
66 year old house.

I'm wondering if there actually is a ground at the gfci. 66 years ago they might have used cloth sheathed NM cable and metal boxes.

Some electricians would drag the grounds back through the KOs and tie them all together on the outside of the box, and this would ground the box.

Then maybe a loose/bad neutral on a 3-wire range circuit or cord

I agree with getting an extension cord from a source with known ground and start there
 
James L said:
I'm wondering if there actually is a ground at the gfci.
Click to expand...

He said there wasn't. GFI just to replace a regular ungrounded receptacle.

Hate to say this, but this is the reason we require grounding conductors and 4 wire range circuits. I would seriously consider upgrading your kitchen wiring rather than putting a band aid on it.

-Hal
 
hbiss said:
He said there wasn't. GFI just to replace a regular ungrounded receptacle.

Hate to say this, but this is the reason we require grounding conductors and 4 wire range circuits. I would seriously consider upgrading your kitchen wiring rather than putting a band aid on it.

-Hal
Click to expand...
I know he said there wasn't. But I've seen dozens of time the exact scenario I explained, with grounds actually being there but made up on the outside of the box and unknown to anybody except somebody who's seen it.

That's about the only plausible scenario I can think of. But I'm not there, so I could be shooting blanks, too
 
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