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On Mon, Nov 4, 2024 at 12:28 PM, Bob wrote:

You mentioned never open the neutral. Earlier talking about a shock by touching the stove and refrigerator, I mentioned it could possibly be an open neutral. Do you agree?

Bob W4JFA

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Hi Bob,

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Hmmm... interesting.I suppose it's possible. Although, if the neutral were completely open, one of those appliances would probably not be working correctly. It is possible that it could be a "bad" neutral connection (high resistance), somewhere on the neutral circuit,? but even then, something would probably be malfunctioning.

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But (IMHO),? getting a shock from two different appliances is an indicator of a hot-line shorted to the ground/frame (like a defective heating element in the stove, or a defective refrigeration compressor, fan, etc, in the fridge)... combined with a bad (or improper) grounding conductor. One of the two appliances is "hot" relative to ground.

The original poster stated that both the fridge and stove were '50's vintage, and were both replaced poste haste by his LL when the LL's own son realized the leakage was real.

It is likely that there was sufficient leakage capacitance between the motor windings in the fridge compressor and its metal case, and perhaps other electrical components, as to cause a sufficiently-high leakage current to flow through the appliance's chassis to be easily detectable by a human body. It only takes a few tens of NANOAMPERES leakage current for the human body to be "shocked" by voltages as low as 24 volts. There is also capacitance between the appliance itself and ground, which causes that leakage current to vary accordingly.

Dozens of years ago, when I was very young, I experienced this effect causing varying potential between my parent's old 1950's vintage refridgerator and the kitchen concrete floor simply by opening the door; when the door was opened, the compressor would shut off (but the little 20- or 25-watt, 110V bulb would come on). You could still get a little "tickle" by running the back of your finger along the chromed door handle; but when the compressor was running, it would be a wholesome SHOCK if you were barefoot! My brother, I, and my parents all learned to open the fridge by tugging on a dry towel draped over the chrome handle. It didn't take my dad long to figure out what was going on; he was an electrical engineer well-versed in such things, after all 8-) I still remember him disassembling the fridge, trying to figure out where the leakage was coming from. Eventually, he'd pinned it down to the compressor motor itself. He solved the problem by running a separate ground wire between the fridge and a cold water pipe nearby under the sink; no more unpleasant shocks at midnight when looking for a cup of cold milk! Mom, of course, didn't like this at all and it wasn't long before we moved (we were renting at the time and the fridge belonged to the landlord).

We hams experience this leakage current often in ungrounded old tube equipment that have large capacitors bypassing the AC line. These capacitors are connected from each side of the incoming AC line to the chassis, which effectively places an ungrounded chassis at half the AC potential! That's why you'll usually see a small spark when you brush a grounded conductor against the chassis of such equipment.

Steve, K0XP