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View Full Version : Another Troubleshooting Challenge


steveparrott
06-17-2010, 11:37 PM
I received a call from a contractor who claimed that he received a serious shock when he removed the timer and touched the timer prongs (the transformer was plugged in at the time).

I troubleshot the problem with him over the phone and was shocked (pun intended) to discover the cause.

Any guesses on what it was?

David Gretzmier
06-18-2010, 08:05 AM
let's see, removes the timer, but plug inside transformer is still plugged into timer. Transformer is plugged into 120 volt outlet. somehow, 120v electricity is going through cord inside transformer instead of outlet inside transformer. timer is on, allowing electricity to travel through timer from outlet on timer, to prongs on timer. as long as timer is plugged in, no one notices transformer is wired wrong internally on plug and outlet. close?

steveparrott
06-18-2010, 10:38 AM
David, I guess that was an easy one for you. The GFCI outlet was wired wrong - neutral and hot reversed. When polarity is correct, hot will only go to the timer receptacle (short slot). If the neutral and hot is reversed then hot goes to the timer plug.

Installers should always check that the GFCI works properly and that its polarity is correct. An inexpensive plug-in device will check these.

David Gretzmier
06-19-2010, 01:26 AM
I will freely admit I do not check this often, unless the outlet is not working. keep the "stump the light guy" questions coming !

RLI Electric
06-19-2010, 07:13 AM
Interesting. Steve, any idea how old the gfi was? I ask this because they are now "smart lock" and typically wont work if there isn't power going to it. I would assume if power wasn't going to it "correctly" as in proper polarization it would not work as well.

steveparrott
06-20-2010, 07:54 AM
Don't know how old the GFCI was, but the electrician had installed two boxes in series; the first one had correct polarity the second didn't. I was surprised that the GFCI didn't trip when polarity was reversed.

Alan B
06-21-2010, 04:51 PM
Interesting. Steve, any idea how old the gfi was? I ask this because they are now "smart lock" and typically wont work if there isn't power going to it. I would assume if power wasn't going to it "correctly" as in proper polarization it would not work as well.

X2

I haven't seen any new GFI's these days (even big box stores models) that work if wired improperly. Most have the fail safe design RLI mentions (at least that I have seen)

steveparrott
06-21-2010, 04:58 PM
I've heard that a GFCI can be wired to completely bypass the protection - especially likely when boxes are wired in series. It's also possible that I didn't get the whole story from the contractor - maybe the second box wasn't even a GFCI!