A few years back I ran a new feeder to a range which had been relocated next to the fridge. That evening I get a call from my customer, calling me all kinds of names, because his wife had grabbed the fridge handle and the oven door handle at the same time. The shock she got was so bad she couldn't let go, and the husband had to knock her free.
I rushed to the house, meter in hand to see what the problem was. Everything on the stove checked out fine, so I put my meter from the casing of the fridge to the stove and got 120 V. I unplugged the fridge and figuring it was a ground problem I checked the receptacle.....it wasn't grounded. I then plugged the fridge into the 120 V outlet on the range, which I knew was grounded, and the fault cleared.
Since that time I've found MANY fridges to have a live casing, and the voltage ranges from 60 to 120. Every one of these were ungrounded, either because of old wiring or the ground prong was removed on the cord end. The casing of the fridge can be checked quickly with a "Volt Tick" tester.
I have only seen this happen on fridges - not on other appliances. Have any of you run into this before? And what would cause the casing to become live when the ground is lifted?
Haven't run into it just on fridges, but have on all kinds of other appliances. As I don't fix appliances, I usually stop there.
Other than a basic light circuit in the refer, the only other electrical componants are the thermostat, and the compressor. The light or thermostat wiring could short to the frame... But the most likely culprit would be the compressor. Most household refer compressors are hermetically sealed in an dieltric oil case. The oil can become contaminated if the refer is leaking, or an indirect short inside the compressor could give you some strange voltages, as it is going through the motor to the case. Anyway, not a good item to not be grounded. That ground is nessesary to clear the fault (Short or indirect short) by tripping the breaker or fuse. Thats what the EGC is for, ensuring that exposed metal parts are the same voltage. It used to be that ovens and ranges had the neutral and ground bonded. Then if there were a neutral problem elsewhere you could get neutral to ground current. Which is more painfull than a simple shock IMO. But sounds like your customer got "locked on". I have been once, and it was one of the most frieghtening experiances in my life.
Mark Heller "Well - I oughta....." -Jackie Gleason
Re: Hot Fridges#56162 09/16/0509:58 AM09/16/0509:58 AM
I've seen this a few times as well. Usually with ungrounded older units and some with unpolarized plugs. Could be a compressor shorting to ground, a chafed wire touching the frame, a neutral to ground connection with the unpolarized plug reversed. This is why I always carry the ticker. Bring your ticker to hotels that you may visit and see how many hvac units as well as desk or floor lamps that are live! Scary stuff, especially since many of these hvac wall units (ptacs) are running at 277 volts. Anybody who's ever worked in a hotel knows why, $7 an hour maint. personnel repairing things they don't understand.
Re: Hot Fridges#56163 09/16/0511:02 AM09/16/0511:02 AM
I think you are looking at the real reason why refrigeration trips GFCIs. The compressor has a ground fault! It may also explain why older fridges pull more power, That fault going out the ground pin is heat somewhere.
Re: Hot Fridges#56164 09/16/0511:22 AM09/16/0511:22 AM
A household refer has a small fan to blow air across the condensor coils. They can be as cheap as 20 bucks, or up to around 100 or so in the built in expenso models. I have seen these fans windings go bad before and cause a ground fault condition on the fridge frame. The reason I mentioned cost of fans is the cheap ones seem to be worse about this. Another thing to do when checking a fridge is shine a light in the dark spots under, or behind. Mouse droppings are sometimes a good sign leading to finding chewed up power cords, and appliance wiring.
Re: Hot Fridges#56166 09/16/0511:51 AM09/16/0511:51 AM
In my experience it was the light in the refrigerator that was leaking to ground. The insulation around the light was soaked from condensation and allowed a fault path to the metal enclosure. Condensation in freezers, refrigerators and air conditioners is one of the reasons to require their grounding per 250.114 Alan--
Alan-- If it was easy, anyone could do it.
Re: Hot Fridges#56167 09/16/0505:58 PM09/16/0505:58 PM
I had some "shady" neighbors who 'conjured up' a replacement fridge for their place, when the old one stoped working. Then they started complaining of shocks when they touched the fridge and the stove at the same time.
The house was also an older one, without a ground wire. Not that that detail prevented them from installing 3-prong receptacles!
My meter indicated a 120v. case. Unplugged, I failed to find continuity between either the neutral or the hot, and the case. Nor was the neutral bonded to the case. Yet, there was still a "hot" case when the fridge was plugged in! I simply concluded that there was a fault in the fridge, possibly through the compressor. These fine folks were soon evicted, and the fridge replaced.
I've always been a little unsure of my diagnosis, though.....but this thread has re-assured me. Thanks.
Re: Hot Fridges#56168 09/16/0506:18 PM09/16/0506:18 PM
Best fridge I can ever remember us having worked better in the fall than any other time of the year. I was sort of aggravating walking up and down the hill but there was a nice cool drink of spring water waiting for you half way through the trip.