I just returned from a call where the complaint was intermittent shocks being received from the plumbing. I proceeded to amp out the neutrals and GEC. When the air handler is running there is 7 amps returning from the sub panel to the main neutral bus. However, 2 amps of the 7 leave thru the GEC which is bonded to the water pipe. The other 5 leave thru the main service neutral. I re made all the neutral connections in the panel, meter base and weatherhead. There was no change. My thought is a high resistance connection at the pole mounted transformer, so I called the utility to check.

I ruled out any interior connections as the full 7 amps appears in the sub panels neutral, it does not divide till the main.

Barring a hot wire touching a pipe somewhere, am I on the right track here?

Just a shot,is the house fed by a well?If so is there a water softener? If so check to make sure the outlet for the water softener controls is actually 120 volts from a true 120volt circuit. Water softener companies around my part like to do their own electrical and steal a leg off the 240volt well circuit and use the ground for their neutral. Just a shot but it might be as simple as that.

No well, no water softener. Gas water heater. It's a very modest 50 + year old home in the city. Occupied by it's original 80 + year old owner.

I know the dirt is not supposed to be a current path but there is really no way to stop it. When the ground is wet around here I have a few amps on my GEC too. If I go out to the pole and look at the ground wire coming down to their rod it is carrying a similar current.

If this buiding is served by a metal underground water pipe system and there are other buildings in the area, it may be normal. Under these conditions the metal underground water pipe is connected in parallel with the grounded conductor per the code rules.
Don

I'd suggest arranging some down time, and metering for current on the GEC with the main _off_.

I'd also try to narrow down the locations where people are getting shocks from the plumbing, and look for non-bonded metal in those locations.

-Jon

Don,
I understand how there are parallel paths here, I just thought that 30% of the return current seems high. But if I really think about it, if the water piping system was in great shape electrically, it could conceivably carry half the neutral load! This seems a bit scary to me! But the only reason I can think of why the current would back up into the house plumbing is a bad connection at the service neutral. Sure maybe 2 amps is acceptable at the GEC, but not at the kitchen sink!

Jon, I did pull the meter and the neutral current dropped to zero on all conductors. That is how I verified the current was from the dwelling in question.

Once the POCO re splices I will have to go from there. Maybe I will have to start looking to see if someone lost a neutral and tagged on to a water pipe to fix it. The whole house is two wire, no grounding conductors.

There are three common items I know of that cause this problem

1. Metalic water pipe between houses/buildings with a common transformer serving them and one house has a high resistance grounded service conductor.

2. A high resistance grounded service conductor, simular to # 1.

3. A very low ground electrode impedance.

First thing I would do is turn off all the breakers and determine if the current is from an outside sources (like comming via water pepe) or generated within. That would give you a good starting point.

BigB I would turn off all the circuits, place the meter on the GEC then turn on each circuit one by one to see if one particular circuit is the culprit or if it is a cumulative problem.

Please post back to let us all know what you found.

I did turn everything off, the current disappeared. Current appears whenever any load is turned on at the home, indicating it is from within that home. I am going back next week after the POCO has been there. Maybe like Don said this current is normal, but if the neutral connection was bad wouldn't this cause it to back up into the house plumbing since the water pipes are most likely also high resistance from all the connections/meter etc?

Bigb,
Are there any interruptions such as a water filter near the water main without a bonding jumper around it ar a missing jumper around the water meter? Also, I'm sure you have already checked the lugs at the neutral in the panel as well as the meter housing...Sure sounds like a neutral going bad.

50 yr old house, I start thinking K&T... Maybe an outlet or two with grounds to plumbing all over the house, which was acceptable for grounded outlets for some time... A short to unbonded plumbing. Did they have any plumbing work done?

50 yr old house, I start thinking K&T

50 years would put the house being built in 1955. That's the time when they started to add the ground bonding tape to type AC, first appeared with 12/2 and 12/3. Many houses were wired with AC. NM was popular then too, the fabric covered type with the undersized ground wire.

In short 1955 was decades after K&T.

-Hal

That was the way our 1954 house was wired. My understanding was if you had a government backed loan like "GI" it was required to have a grounding path in the wiring method at that time. That is what my dad said anyway. One of my first electrical experiences was retrofitting receptacles to 3 prong with my dad and granddad (an electrician)
I know in 1971 when I bought my first house of my own they told me it wouldn't pass the GI bill inspection but they wouldn't say why. Now I assume it was the aluminum wire.
It didn't bother me since I did have the down payment and they matched the GI interest rate.
The whole "GI inspection" thing may just be for folks in the DC area since others in flyover country have never heard of it.

BTW my ex still lives there and has never had a problem with the wire.

Well here's an update. The POCO re spliced at the xformer and weatherhead. No shocks for a week, but the current was still on the GEC just like before, so I have to conclude that it is normal like Don said. The shock must come from another source. Sure enough, they called today, the Old Lady got zapped again, pretty good they said. Also the caregiver. They took note of everything that was on at the time as I had asked them to do. 2 kitchen lights, the bath light and the microwave. Tomorrow I will go check these circuits.
Also I had another thought. The water mains are out front, in the street, with each house having it's water service entering at the front. The electrical services are in the back, they are bonded to the piping at the back spigot. Our AHJ's allow this, even though the code says the first 5 feet where it enters the building. Now in light of this, suppose a neighbor had an open neutral and their current was returning thru the water pipes. This current could enter the neighboring homes at the front, pass thru the homes piping then out the back where it would find the neutral at the bond. If the interior piping had some resistance, this would allow for a shock when another path, such as the Old Lady, was introduced, could it not? Or am I thinking too hard???

Just as food for thought:

In the 1950s, this was a common way of obtaining an equipment ground for the bath, kitchen, and laundry circuits:

BigB,
What are the tow items that are being touched when they receive the shock?
Don

greftwell

The 'GI' housing standards began with the 'VA loan' shortly after the government noticed 'junk shacks' standing as collateral in the post-war real estate boom. Take a look at "Mr. Blandings Dream House" which BTW is an excellent tutorial for change orders.

The same standard was applied to FHA loans, too.

It was these standards that kept carpeting out of tract homes until 1964, hence hardwood everywhere. Such standards included what size space constituted a bedroom, etc.

We now accept these norms as part of the building code to be universally applied, but they all came from this legislation.

IIRC the FHA loan standard still is the basis for all residential finance. It has been absorbed by all other consequent entities such as FNMA ( Fannie Mae } which handles a staggering percentage of wholesale residential finance.

( Almost all local real estate lenders kick their loans up to FNMA (sell them) in hefty bundles and retain an on-going loan service fee. Properties that don't meet the standard are not acceptable collateral to FNMA. The lender cannot resell the 'paper' (the loan) and that pretty much kills the deal.)

In its early years these standards were almost always tougher than local building codes -- if they even existed. That's why no matter how great the building boom no one cranks out the hole-in-the-wall shacks that were so common in the 1920's Florida and New York booms.

You'll still see closets pitched as bedrooms in Hawaiian rentals, though.

Don, I can't be sure if it is the faucet and metal sink or the faucet and the floor. I am pretty sure it is the faucet and metal sink since they said they had shoes on.But if you ask them, they claim it is from the water itself. It is an older house and the faucet is wall mounted, no contact with sink. Are you thinking I should just bond the two and call it a day?

No. There is something that is energizing an unbonded metallic object. You need to find the voltage source. Maybe bonding would cause enough current to flow to open the OCPD, but it could be a high impedance fault, and the bonding may just cause enough current to flow so that a fire results.
Don

just a thought,
The only times I've ever run across someone getting shocked by the plumbing, there was a bad cal-rod in the water heater.
Is the W.H. electric or gas?
something to check.

Lamplighter, it's gas.

Well upon more investigation I went to the neighbors house and found 3.5 amps on leg A, 1 amp on leg B. According to my math this should put 2.5 amps on the neutral. Well there was only 1 amp showing up on the neutral. Trouble is, there was zero on the GEC. I can't figure where the missing 1.5 is going. My only thought is this: If the neighbor has a neutral to ground connection inside the house, and a poor neutral connection at the drop, maybe there is current leaving out the front where the water pipe enters the house. Remember, the water services are in the street while the electric is in the alley. This would put the missing current out the front to the water main and back into the old lady's house where it would travel from the front, thru her kitchen plumbing, then out thru her GEC which is bonded to the plumbing in back. I have to wait for the neighbor to be home so I can get them to switch enough loads on to load up the neutral, at which point I will amp out the water pipe.

Hal, I have seen places around here with original K&T, (TW plastic wire insulation, in colors even) installed straight up to the mid 60's. With original permits on the building/in the panel for proof. Many, if any grounds, were to the nearest cold water. It would seem a few guys back then stuck to thier antiquated wire system until they retired. (Like old dogs and new tricks.) Another real shocker, is that you'll have occassion to see 3-wire circuits in some of the early to mid 60's houses in K&T as well - SCARY! Something to watch for when doing panel changes here.... (I usually reduce the ciruit load in re-models by re-doing the plugs, and put all of them on the same phase, and two wire circuits. If i can....)

These houses are 2 wire cloth covered romex.

BigB
As Don has mentioned, it would seem there is some kind of fault in the house that you are dealing with.
you mentioned 2-wire, is there an equipment ground conductor with the 2-wire?

When you started to turn the circuits on, did you do it one by one or by using the main?

Do you have access to a gauss meter?

PCBelarge,
Thanks for your interest. I went through the house and turned on everything I could find. Then I ran a 50' extension cord in from the main to provide me with a ground for testing. I could get no current from the plumbing.

The wiring has no grounding conductor.

One way I will prove if it is coming from within the house or coming in on the water pipe, I will move the water bond from the back of the house to the front instead, where the water main enters the house. This will give any incoming current a low resistance path around to the main neutral instead of thru the house plumbing.

Then if the issue still occurs, I will know it is internal.

I still need to check out that neighboring house, did you read my post about the neutral current there that didn't add up?

[This message has been edited by BigB (edited 11-02-2005).]

The shocking incidents also only occur two to three times a month,and last only a short time. Makes it tough to figure out.