Pipe Shock?

[jaredfriesen]

Thanks in advance for comments on this issue. FYI, I am an EIT 1 year out of school.

My aunt was telling me she was shocked in her garage. It happened when she was somehow touching both a light switch and a pipe. I didn't think to ask her if she was barefoot, but lets assume she was. Also, she says the shock was strong enough to make her scream.

I am thinking the light switch has nothing to do with it. Does it sound feasible that the pipe is the systems ground, but that since the concrete slab may be grounded better than the pipes, the current chose her and the slab as the ground path of least resistance for all the load in the house?

I did tell her she should call an electrician to take a look as this is a safety issue, but I am also interested in why this may have happend.

Thanks again.

 

[bennie]

Re: Pipe Shock?

The plastic toggle, on light switches, become a conductor with deposits of salt from the fingers.

Grounded metal operators will stop this hazard. The garage area is probably high in moisture content.

 

[iwire]

Re: Pipe Shock?

EIT? Electrician in Training?

If you have a voltmeter you could carefully put a lead on the two spots that your aunt touched and see if you read any voltage.

 

[bennie]

Re: Pipe Shock?

Was it a 120 volt scream? Bob, the aunt already checked for voltage

I am an engine ear in training too.

 

[tom baker]

Re: Pipe Shock?

There is a voltage difference between the switch and pipe. She may of touched on the metal faceplate screws. The switch itself could be energized by improper or shorted wiring. Test to the pipe with a voltmeter. Turn off the circuit. Test again. if the voltage goes away, take a look at the switch wiring.
Or the pipe could be energized, which will be harder to find the cause for.

 

[jaredfriesen]

Re: Pipe Shock?

Engineer-in-Training

I would think the problem is not with the light switch because she has never had any shock with it before and it operates properly.

I am assuming she usually does not touch the pipes at a time when she may be grounded better than them, otherwise she would get the shock from all her faucets, right? I do not live in the same town she does to experiment, but it seems it would be difficult to measure the potential between the pipe and concrete - touching the tip of the lead to the pavement. Maybe if I pool some water on the floor

Thanks for your input.

 

[bennie]

Re: Pipe Shock?

EIT: The switch can perform perfectly but the toggle can still be energized when coated with impurities.

I have seen a shock on a hand when the finger touches the toggle and the hand contacts the metal cover.

The cover in your situation is likely plastic.

The rod completed the circuit through the human.

Wipe down the switch handle with contact cleaner solution.

 

[hornetd]

Re: Pipe Shock?

Don't neglect the posibility that the receptacle was the grounded surface and that the pipe is not bonded and has an elevated touch potential because of an electrical fault in a device in contact with that piping.
--
Tom

 

[bennie]

Re: Pipe Shock?

Tom: I agree you have a good point.

I am sure we all agree, this should be corrected before someone has a bad day. The next scream may be a dying gasp.