Shower Shock

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daveselectric

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A customer had installed by a electrician one exhaust fan and one exhaust fan heater combination. This was installed as old work and had been fed with a 12-3 NMC home run. It appears that when these fans are turned on, and one is taking a shower and steps on the drain, they receive a shock.

The home was remodeled several years ago and the vent stack on the 1st floor was re-routed and replaced with PVC. The upper floor still has the galvanized and cast pipe.

When I run a wire from the hot side of a receptacle to the shower drain with a Wiggy in the middle, there is no potential or continuity with the heater / exhaust fan off. When the exhaust fan / heater is turned on, I get a 120 volt reading.

Any thoughts or ideas?

Thank you,
 
WOW

I would start with taking a look at all the splice in the fans and switch box.

After seeing if the work was good I would break the splices and use a continuity meter from the tub drain to the conductors to find which has continuity to the drain.
 
No EG in that 12/3 or not connected? Check for a wire faulted to ground someplace after the switch. Heat element bad? Motor? The cast iron drain line could very well be intact, even though the Vent stack has been replaced. We always bond these old drain lines. Just bonding the line now will not correct the problem but it may make it "disappear".
 
daveselectric said:
When I run a wire from the hot side of a receptacle to the shower drain with a Wiggy in the middle, there is no potential or continuity with the heater / exhaust fan off. When the exhaust fan / heater is turned on, I get a 120 volt reading.
Click to expand...

The first thing I think of, is the recptacle switched with the exhaust fan/heater? If so, then you would expect to read 120 between Hot and the drain (which is metal and may be near the potential of ground).

Take your DMM (not a wiggy) and connect one side to the EGC terminal at the receptacle and the other side to the drain and measure the potential.

edit to correct second sentence
 
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I have seen bootlegers ground to stack pipe. These bootleggers do not know that by doing these they are creating a potential fatal enviornment.

I have also seen a bootleger use the box for a neutral.

The wiring is new. We have re-fed from the attic and respliced to assure there ar no kinks or nicks in the wiring.

Please keep the ideas and suggestions coming.

Thank you so much
 
Dave,

If you get 120 difference between drain and hot when heater and fan is on that is telling you one side of your measurement is hot(120) and other is close to the potential of ground. If the drain was hot when you turned on the fan than there would be no potential difference between the drain and the hot, both would be at 120.

Is the drain line above the potential of the EGC or GEC? If so, then current can flow from if one touches the valves that turn on the water and at the same time touch the drain line.
 
Just a thought.
If that is a H/L/V unit, it requires a 4 wire feed....3 hots, neutral and ground.
If the installer used the white in the 12/3 as a hot conductor and used the bare ground as the neutral, it could cause your problem.
It would depend on how, where (and if) the drain pipe is bonded to ground.
It's possible to create a parallel (return) path through the drain, (and the person) to the shower head.
steve
 
I had a similar situation in a kitchen at a residence several years ago. After two hours of searching and at the point where I was going to give up I finally checked the light switch. It happened to be one of those older "quiet" switches with mercury in it. I was getting 120v between the faucet and the metal rim around the outside of the sink. I actually hooked up a keyless fixture and the bulb lit. Anyway, I traced the fault to a junction box above the ceiling light fixture where the HO had 5 armored cables entering a 3 1/2" JB. Four of the cables were secured properly to the 3 1/2" box but the switch leg cable going down to the switch was merely stuck into the back KO. Somewhere along the line the armor must have cut into the switch leg. The armor was not metallically touching anything that was grounded. That, in turn, somehow made the metal trim ring around the sink hot (I didn't trace that mechanically because once I corrected the armored cable the fault disappeared).

Anyway, this may not reflect your situaition exactly but somewhere along the line your tub and water lines are no longer bonded together to ground. Anything could have happened during the renovation. The plumber could have used PEX pipe and as such would have separated the copper water lines from being grounded. The plumnber could have inadvertantly burnt the insulation off an RX cable while soldering a fitting. When they set the tub in they may have shot a long sheetrock screw through an RX cable. No matter what may have happened you're going to spend a lot of time trying to find this one.

The only thing I would suggest is the following : make sure the fan/heater switches are off; tie a # 14 wire onto the drain and bond the other end to something you know is properly grounded (like the ground port in a duplex receptacle; then turn on the switches. If there is a dead short somewhere chances are it will pop right where the fault is. If this doesn't work, good luck trying to find it.
 
daveselectric said:
Any thoughts or ideas?
Thank you,
Click to expand...
The first thought I had was that every fan I have ever installed in a shower explicitly spells it out that it must be on a GFCI circuit. I am surprised it doesn't have one -- at least I am guessing that it doesn't. Does it?
 
Dennis Alwon said:
The first thought I had was that every fan I have ever installed in a shower explicitly spells it out that it must be on a GFCI circuit. I am surprised it doesn't have one -- at least I am guessing that it doesn't. Does it?
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Dennis, that only applies if the fan unit is in the ceiling directly above the shower space. If it's outside the shower space it does not have to be GFI protected
 
goldstar said:
Dennis, that only applies if the fan unit is in the ceiling directly above the shower space. If it's outside the shower space it does not have to be GFI protected
Click to expand...
I know that but I thought that's what the OP was saying. I was --i hate this---wrong.
 
iwire said:
I have never seen an intentionally bonded waste line.

Is that a local requirement or something you chose to do?
Click to expand...

We see enough old houses with 1" to 2" galvanized sections of drain, some even with all copper, top to bottom, and they sure qualifiy has other "local metal underground systems". Also cuts down on that tingle from the bonded shower head while standing on the unbonded metalic drain. Call it stray voltage if you are inclined.
 
Dave, is the F/L/H fed from a subpanel by any chance? I once had one like you describe, the neutral was connected to the grounding bus in the subpanel, the feeder grounding was emt over the roof. Once the emt separated the neutral current backed up and energized a bunch of stuff, including the plumbing.
 
daveselectric said:
When I run a wire from the hot side of a receptacle to the shower drain with a Wiggy in the middle, there is no potential or continuity with the heater / exhaust fan off. When the exhaust fan / heater is turned on, I get a 120 volt reading.
Click to expand...

Now I'm confuzzled.

Where is the customer getting the shock between? It sounds like the drain is either floating (fan off) or grounded (fan on) so where the source of voltage? Or is the drain actually at some intermediate voltage between 0 and 120V with respect to ground with the fan on, and thus the shock comes from drain to ground...?
 
Make sure the cold water is bonded and is bonded in the panel as well. Sounds like it has nothing to do with the fan since its a direct homerun. I think the problem has always been there.
 
Dean83169 said:
Make sure the cold water is bonded and is bonded in the panel as well. Sounds like it has nothing to do with the fan since its a direct homerun. I think the problem has always been there.
Click to expand...

If the symptom comes and goes with the fan being turned on/off then I would respectfully disagree and say the fan does have something to do with it.
 
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