Volts leaking to ground rod

Discussion in 'Electrical Forum discussion & Blog' started by Homeownerinburb, Feb 19, 2014.

  1. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    Got a call to investigate an arc of electricity where grounding conductor to water supply coming into house was interrupted. Apparently there is a ground rod as well.

    I want to guess that some large item is leaking volts into the ground loop.

    If I find an electric stove, that is my first suspect.

    Any thoughts? I'll be looking at it first thing tomorrow.
  2. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    4,141
    Location:
    NW Ontario, Canada
    I would suspect a bad neutral. I had a case once with an open neutral where there was so much current going to the water supply that it warmed the water.
  3. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    You mean to say at the panel or the top of the pole.

    Yes, I will certainly be poking around the panel looking for 120 v to both legs. If one of them is more than two or three volts off the other, I get suspicious.
  4. ActionDave

    ActionDave Electrician

    Messages:
    361
    Location:
    Colorado
    I agree with that Canadian up there, bad neutral. It could be at the service, at the pole, could even be a different house and now your customer's water pipe has become that neighbour’s neutral.
  5. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    And THIS is where troubleshooting becomes a bitch!
  6. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    What tests do you recommend?

    I have no problem calling it a bad neutral when one leg is 100v and the other is 140v, but one needs to be pretty dull witted to not see that.

    What if the voltage leaking out is on the order of 30v?
  7. ActionDave

    ActionDave Electrician

    Messages:
    361
    Location:
    Colorado
    Likely the same as you. At the service panel- Phase to phase, phase to neutral, phase to earth conductor; turn the main off and look for changes. You need at least 15V difference phase to neutral before you can rule out just plain old voltage drop from the POCO IMO.
    If you have a analogue meter check or a low Z on your digital check voltage between the ground rod and the neutral. Should not be very much volts.

    Put an ammeter around GEC. Turn off the main. Do the same at neighbour's house.

    Go out and look at the pole. If you talk to the POCO try and find somebody that has some service and trouble shooting experience on their end too.
  8. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    All good stuff except I don't expect to be poking around in the neighbor's panel.

    I do expect to be calling the power company, very likely. They are very responsive here.
  9. DonL

    DonL Jack of all trades Master of one

    Messages:
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    Location:
    Houston, TX

    If the neighbors are on a different transformer, I see no need to bother them.

    If you measure any current flowing on the Ground Rod conductor or water pipe ground, You should call the Power Company. If you do not have the proper tools, You should call the Power Company.

    You should not disconnect or mess with anyting that is arcing or throwing sparks, unless you have a Electrical license.

    A shorted element should pop a breaker if everything is wired and sized properly.


    Good Luck.
    Last edited: Feb 20, 2014
  10. hj

    hj Moderator & Master Plumber Staff Member

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    Location:
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    quote; could even be a different house and now your customer's water pipe has become that neighbour’s neutral.

    That would be such a "stretch" that I would not even consider it. Possibly an electric water heater with a bad element, or as stated a failed neutral from the power company. I once disconnected an electric water heater and when I separated the union I had an arc. EVERYTHING in the house which was turned on immediately burned out when they were hit with 240 volts. I had to carry the huge console TV outside because it was smoking. The neutral had failed, and they connected to the ground rod with a piece of BX metal cover which had rusted away so the entire neutral "duty" was being done by the water system and since they had made the ground connection to the hot water, the current was going through the water heater which caused it to start leaking. Separating the union "undid" the whole process. Fortunately, I had had enough experience with poor wiring that I separated the union by hitting it with a wrench, rather than grabbing the two sides and pulling them apart, (which has killed many plumbers when they remove water meters without "jumpers" and some variation of this is occurring).
  11. Reach4

    Reach4 Well-Known Member

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    Location:
    IL
    Call the power company.

    For troubleshooting mainly for curiosity, get a clamp-around ammeter. Measure the current through that ground wire. Kill power at the main breaker. Does that current largely remain? If the current remains, that would show that the neutral conductor from the transformer is there, but if the current is significant, their grounding at the pole is not adequate. I don't know where I would draw the line of being adequate.
  12. DonL

    DonL Jack of all trades Master of one

    Messages:
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    Location:
    Houston, TX

    Just my thought, If a person does not have a clamp-around ammeter, They do not need to be working on a electrical job.


    I could be wrong.
  13. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    All good stuff, guys.

    Not likely an electric water heater. Gas appliances are very common around here. There are some electric stoves, although I have no idea why.

    Yes, the amp flow test is on my list.
  14. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    This particular utility grounds all of its transformers, so if I do find current in that test, then they will certainly be out like a flash to check it out.
  15. BobL43

    BobL43 DIY Senior Member

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    1,794
    Location:
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    I have 2 Amprobes and a Bell current gun, so does that mean I am qualified? I have no plasma suit, so I am definitely not.
  16. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    4,141
    Location:
    NW Ontario, Canada
    In a multi-wire circuit, only the differential is carried by the neutral. If both legs are carrying the same amount of current, the neutral carries none. In some cases, the neutral may be a smaller gauge wire for that reason.

    However, if the loads are off-balance, meaning that one leg carries next to nothing, then the neutral will carry about the same amps as the heavily loaded leg. When that happens, you may experience a voltage drop across the neutral that then is picked up by the protection ground. Even if the neutral wire is the same gauge as the two legs, there can still be a voltage drop in such a circumstance.
  17. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    So. What I found:

    The tenant had been doing some sprinkler work out front and for some reason wanted to take out the pressure regulator from the plumbing going into the house.

    He reported seeing an arc as he was manipulating the components and then got a sizable shock when he grabbed the two components with his two hands (!).

    I arrived and saw that the bonding cable for the panel (newish) was clamped to the plumbing on the HOUSE side of the pressure regulator. The inspector for the area wants it to be on the STREET side of the regulator. Me? I like being certain that the plumbing in the house is well bonded. When I do and install like this, I bond on both sides of the pressure regulator and then jump to the ground rod.

    I found as many as seven amps running down the ground cable toward the plumbing and the ground rod in the front of the house.

    I took the pressure regulator apart and found a 45v potential across the joint, so there was definitely enough there to get your attention, especially with wet hands.

    Then I released the grounding cable from the plumbing, and then from the ground rod. And found essentially nothing. Less than three volts. And I could not recreate the 45v I had moments before.

    I opened up the panel and got a similar reading. I shut off the main power and got nothing. And both legs were within a volt of the other to neutral/ground. So the power company was absolved.

    The tenant's washing machine stopped running and suddenly the amps pouring down the ground dropped to 0.3.

    This place was built in the late '30's with flex and cloth/rubber conductors, which are still in place.

    I am inclined to expect a system that old to leak about a third of an amp, who disagrees?

    I ran the (gas) dryer as well, and it caused the leak on the ground (at the panel) to go up to nearly 4 amps, same as now the washer was doing. I replaced the receptacle, and of course found what modern standards would call a grossly over filled box (cloth/rubber, and the connections are twisted together and soldered, then wrapped in very bulky cloth tape!)

    It is an old house with old wiring. A full rewire with a dedicated ground everywhere is in order, but not going to happen anytime soon.
  18. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    Yeah. Sure wish I had me a plasma suit.....

    For when I am doing a domestic repanel.
  19. Reach4

    Reach4 Well-Known Member

    Messages:
    2,636
    Location:
    IL
    Tell us more about that. What are you measuring and how? Are you measuring the current with a clamp ammeter on a wire going directly to a ground rod or plumbing? That doesn't sound right to me.

    I am no expert on this, but I think more info is needed.

    What voltages do you have across your 120 VAC outlets under those conditions?
  20. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,559
    Location:
    North Carolina
    First there is no such thing as leaking voltage. Voltage is a difference in potential or the amount of pressure that pushes electrons through a conductor. Amperage or current is what flows, this is how we measure the amount of flowing electrons.

    Current is always seeking it way back to the secondary of the utility transformer. If there is current on the grounding electrode be it a pipe or rod then there is a problem with the neutral of the system. If the water system is a public utility then it problem could be with someone else’s neutral and the current is seeking it path back through the electrode and the neutral of the house that the problem is detected.

    At any rate current on an electrode should always be called to the attention of the utility company instead of trying to figure out what the problem is by yourself. If the power company gives a clean bill of health then start your trouble shooting but without knowledge it is like peeing into a fan.
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