Shocking Shower

[Stormin Mormon]

Three or four years ago, my church set up a summer camp retreat. They built a mess hall, cabins, and a couple shower and toilet buildings. Cement slab, wood frame walls. Shingled roof.

The campers are complaining that when they touch the shower handle, they can feel an electrical tingle. The WH is propane gas fired. The propane line (black iron) also goes to a Rheem Contour furnace, which supplies an overhead heat duct.

I took a VOM and length of copper pipe, used that to check from the shower handle to the drain. Got 5 volts AC. Doesn't happen when the power is switched off for the furnace.

I traced the wiring, the furnace was only put in a year or two ago. (Nobody complained about shocks until the new furnace was put in.) New, shiny copper wires. I pulled the wire nuts on the neutral and ground. The wires are clean, adequately stripped back, and the wire nuts get a good "bite". The panel box, like the rest of the building is only two or three years old, and nice and new.

The WH has dielectric thread connections at the top, I can see the red plastic at the fitting. From what I can tell, the water main coming out of the ground is plastic.

The questions are:

1) Why would a brand new furnace be leaking power? And how's it getting into the shower? The only other electrical devices in the building are lights, and a couple electric sockets.

2) Why isn't the power going out the neutral and ground?

3) How to safely take care of the problem so the campers aren't being shocked?

My thoughts at the moment, are that the neutral / ground has some corrosion or resistance past the panel. Meaning outside the building. And that the solution is to run a new ground wire out the wall, and sink a ground stake right outside the wall with the panel box. Any other thoughts of how to handle this shocking problem?

[dpb]

Stormin Mormon wrote: ...

You have, almost certainly, a grounding issue. My first thought w/ separate buildings an auxiliary ground is inadequate/missing, but with only a general description not possible to tell much specific.

Need to know how the power is distributed and where the ground(s) are. I'd be a little concerned that your measurement of the voltage is an underestimate from the technique to reach so I'd treat this as a potentially (pun not intended) serious issue. Probably adding a ground directly at the shower head as a temporary pallative would help. Surely there's a good electrician-type in the church that can help diagnose this? Distributed system grounds can be very difficult to trace and a pro should be able to recognize where there's a problem if a needed ground is missing.

[Pat]

I agree with dpb that it sounds like a ground problem. When they put in the new furnace they probably disconnected something. Drive a rod into the ground and ground to that until you can get it fixed.

The good news -- the kids will take fast showers.

[gfretwell]

You should have a ground rod preferably 2, connected to the ground bus in the panel. You should also bond all the metal piping including a jumper around the water heater.

[Jeff Wisnia]

If the plumbing is accessable it'd probably be wise to bond the water supply pipes to the shower valve to the drain pipe before letting anyone use the shower again, then do the overall grounding job properly ASAP.

I'm no lawyer, and never even played one on TV, but since you've told the world about your knowing about this problem in a format which will take forever to disappear, you'd best be carefull lest someone slips in the shower, breaks their spinal column and then decides to go after the cchurch for all it's worth, claiming that "the shock" made them jerk and fall.

Jeff

[BobK207]

All-

Some comments & more questions than answers.......

Sounds like he's got a grounding problem but desn't he also have a problem in the furnace itself?

the resistance from the grounding system to the earth is too high?

& the "ground path" from the grounding system to plumbing, instead of grounding the shower plumbing is actually "hotting it"

but isn't the real problem in the furnace? some how is the power leaking over to furnace frame & thereby "hotting" the furnace frame & ground?

now you've got some juice in the (inadequate?) ground system that is trying to find it's way back to earth.......the shower plumbing & the showerers are part of this ad hoc path.

shouldn't the fault (nsulation? wire contacting bare metal?) in the furnace be looked into? maybe a fault in the blower motor?

Grounding is part of the issue but isn't the source of the voltage of equal importance?

cheers Bob

[Stormin Mormon]

I'm thinking a neutral problem. If th ere was a good neutral, then the white would carry all the wire.

I've been wondering if it would create a different effect in a boys versus a girls shower? The one which is shocking is the girls, and they don't like it. I can just imagine in the boys "Kewl! Hey everyone come over and check this out!"

[Stormin Mormon]

I was thinking also a jumper from hot to cold pipes at the shower. The dielectric connection reduces corrosion. But it doesn't drain power through the cold water inlet.

[dpb]

Actually, that makes me think of something should have mentioned previously -- perhaps the new installation w/ the dielectric union on the gas line broke a previous ground path. Jumper it w/ a ground and see if it changes symptoms.

As for the proposed "solution", that _may_ be the right solution, but as noted previously, w/o knowing the actual distribution what is right and adequate isn't possible to say for sure.

One thing to be careful of in such a situation is the possibility of a ground loop existing and having a significant potential between various ground points. In that case it is possible to get oneself across this w/ a possible significant current flow which obviously is a bad deal...that's why I recommended an experienced electrician take a look at the installation.

--

[Stormin Mormon]

Water supply bonded to drain, I did think of that. I'll have to go back and see if the pipes are accessable. My guess is probably not.

[Stormin Mormon]

The shower building is fairly remote, not that makes a whopping lot of difference. A bad neutral can happen even in apartment building.

[Wayne Whitney]

There's definitely a problem in the furnace or the circuit feeding it.

Slight clarification: the juice is trying to find its way back to the secondary winding of the transformer powering the service. Because of a fault, the normal return path using the neutral conductors is now paralleled by a path involving the shower plumbing and probably the earth. Because of some problem with the EGC (equipment grounding conductor) system, the fault did not hit the desired "low-impedance return path" to the service which would trip the breaker. Return paths using the earth will almost never be low enough impedance to trip a breaker.

Cheers, Wayne

[Toller]

There could be a short from the hot or neutral, or the ground could be bad. Could be any damned thing. I don't think you could actually feel 5v; but perhaps there is really more than that. Go to the nearest outlet and test H-N, H-G, N-G. Assuming they are all correct, test them all to the drain and to the shower handle. Then test from the gas pipe to a ground etc. etc. until you isolate where there is unexpected voltage. If you plumbing is plastic, I don't see how any voltage is getting to the shower, unless you have really really really hard water.

[mm]

Why is the furnace on at summer camp?

Because the shower makes them cold when they get out wet? Using a heater is no way to rough it. At summer camp there should be no heat but what the sun provides.

I think, whether they still have a legal responsibility to fix this or not, that the furnace company should know what a rotten job their installer did, and that they are in the best position to fix it.

"I thought you would want to come out and fix this." "As part of your original [uncompleted] installation". "Before some child gets hurt"

[Zephyr]

The furnace is seeking ground through the gas piping system to the water heater and perhaps from there to the showers.

Ground the water system with an 8 foot earth rod and the neutral buss from the service panel. Read UEC #250.50 [Grounding Systems]. Check the neutral at the appliance and make sure it has both, a separate load carrying neutral and earth bond [ground.] Be sure the panel / sub -panel both are grounded as well. Check and tighten all electrical connections, pay particularly attention to the grounding system.

[tnom]

Through the air. AC at 60hz acts like a radio wave in that it can induce a voltage in a conductor near by. Any wiring, motor or transformer will radiate electromagnetic radio waves. The plumbing is the antenna that is being induced.

The felt voltage is not coming directly from the wiring.

The shower head is the hot lead of the voltage source and the wet ground or drain is the other conductor. Electricity has to have a path to be felt.

Short the two leads. The shower head and the floor drain.

[John Grabowski]

Are the ground and the neutral separated in the new subpanel or are they bonded together? Do you have a good grounding conductor from the subpanel to the main panel? Is there a good ground at the main panel? By good ground I am referring to two ground rods and a connection to the main water line.

Any chance of getting some pictures of everything?

[Stormin Mormon]

The furnace was originally installed so they would not have to drain the pipes in the winter. We do zero F now and again, and pipes do freeze.

From what I could see, the furnace guys did fine. I think it's the electrician who made the run of wire to the shower building that didn't put in adequate neutral / ground.

[Stormin Mormon]

The furnace has both a neutral and a ground. I know -- I checked. Is 8 foot the standard? I was in Home Cheepo last night, and they do sell 8 foot ground rods. Is a shorter rod acceptable? Eight feet sounds like a lot of sledge hammer work.

[Stormin Mormon]

CY: The grounds and neutrals go to different bars. Beyond that I don't know.

Do you have a good grounding conductor from the subpanel : to the main panel?

CY: There is a conductor. But the fellow who runs the camp didn't seem at all pleased with the electrician. So, it may not be good.

Is there a good ground at the main panel? By good : ground I am referring to two ground rods and a connection to the main water : line.

CY: The panel in the shower building has no signs of ground. The wire goes out to a cement box, which sits maybe 6 feet from the building. I see no connection from the panel to the water line.

: : Any chance of getting some pictures of everything? :

CY: That is a very wise question. I don't have a digital camera, but been considering getting one.