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When I measure current in the grounding strip coming from my house electric panel to the water pipe using clamp meter I am getting slowly fluctuating value from 1.5 A all the way to 4 A. In my understanding (I have PhD in physics and I work as an electronics engineer, so it is a reasonably good understanding) this strip is normally not supposed to carry any significant current.

Now, this current is not a result of any problem inside the house. The ground and neutral wires are bonded together inside the panel (I've checked), so even if something in the house leaks current to the ground wire this current returns to the neutral in the panel, it does not go into the grounding strip.

I am reasonably sure that utility neutral is bonded to earth at street transformer as well, so ground strip and water pipe and earth is just another way for current to return to the transformer, parallel to the neutral utility wire. But utility wire is 1 inch thick metal conductor and creates a very easy path for current to return, there should not be any reason for 4A of current to go through the grounding strip unless there is something wrong with utility neutral.

Is there any other explanation? I started measuring things because my power consumption is abnormal and I am looking for a reason.

Best regards, Alex.

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    On the way to a possible explanation; Do you have an electrically powered water Heater?
    – Paul Logan
    Commented Dec 9, 2017 at 21:48
  • Do you have grounding rods? I take it your power consumption is abnormally high, right?
    – Jim Stewart
    Commented Dec 10, 2017 at 0:02
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    High resistance connection on a neutral lug in the main panel, meter, or on the pole is a possibility. It happens. It will also worsen over time because the by-product is heat that overtime arcs, burns, expands/contracts etc. Call your power company for a meter and pole connection check.
    – Tyson
    Commented Dec 10, 2017 at 1:47
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    Clamp meter all 4 wires at the edge of the panel. L1 minus L2 should equal N. Also turn off one breaker at a time (or turn off half and do a binary tree search) and see if it stops with a single breaker turn off. If it defies being narrowed down to one or a few breakers, that means something else.
    – Harper - Reinstate Monica
    Commented Dec 10, 2017 at 4:52
  • Answer on comments:
    – gmygmy
    Commented Dec 10, 2017 at 16:00

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Looking at your question and reading your background I am betting you may have a lot of electronics in your house and you actually have two problems. First you are picking current in a ground and second you seem to have an unusual power consumption. When you put them together as single problem it generally boils down to Harmonic Distortion, K-factor. Electronics, as an example a UPS, have a habit of recreating the wave and causing a distortion due to the time lap in the return current in the neutral. Also Electronics have a habit of using the ground as a handshake between components causing a current flow in a ground.

K-factor is a weighting of the harmonic load currents according to their effects on transformer heating, as derived from ANSI/IEEE C57.110. A K-factor of 1.0 indicates a linear load (no harmonics). The higher the K-factor, the greater the harmonic heating effects.

I am not sure but by reading your question I think the water pipe your are clamping to is not bonded back to the single point of reference at your ground. If that's correct you really need to do that. Also instead of trying to troubleshoot the panel try and turn off any electronics in you residence and see if that helps correct your problem.

As far as knowing whether or not this is the real problem with your power consumption. You would really have to run a power analysis to know for sure. FYI this type of equipment runs in the neighborhood of about $5,000.00. So I would suggest you find someone who does this for a living and try and work out some sort of quote if you feel it is necessary.

Hope this helps.

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  • You mean like in Wreck-It Ralph, with the toons running up and down the electrcial wires? That would not account for three amps on the ground leaving the house. Even if he has a fairly serious ground fault, it should return to neutral via the neutral-ground bond in the main panel, not to the water pipe to lots of dirt to the ground wire at the transformer.
    – Harper - Reinstate Monica
    Commented Dec 11, 2017 at 0:46
  • @Harper exactly notice my comment "I think the water pipe you are clamping to is not bonded back to the single point of reference at your ground". The only way you are picking up a different potential in the ground would be if that particular point you are measuring is not connected to the neutral-ground bond. If you remember in the 1980's everyone was having a problem requiring a separate and isolated ground in computer rooms and they began having the same problem user3781341 is describing. To fix it we had to run their ground back to the original ground to establish a 0 reference.
    – Retired Master Electrician
    Commented Dec 11, 2017 at 14:05
  • @Harper - The other problem I see is that with amperage there must be voltage but what is the voltage. So there is current between the two reference points. My best guess is that it would be a harmonic, but I am just guessing. We can't establish the true problem without some sophisticated equipment thus the power analyser. Every other cure is just hit or miss.
    – Retired Master Electrician
    Commented Dec 11, 2017 at 14:13
  • Well my concern is: the current is returning through dirt. Dirt is not a great conductor. The only voltage that should be present in the house is 120V, which he pays for, so try this on for size: what if the voltage is 120V? If so resistance is E=IR 120=1.5xR on the low side, 120=4R on the high side, R is 30-80 ohms. That's exactly what we'd expect for dirt. My theory is the leakage is normal 120 and it's possible his house is floating 120 above neighborhood earth.
    – Harper - Reinstate Monica
    Commented Dec 11, 2017 at 16:14
  • That's a scary notion, @Harper :-). I did clamp SCT013 non-invasive current sensor onto the grounding strip and connected oscilloscope to it. It looks much more like triangular wave than sinusoidal, but it is still 60Hz. My water main is 1-inch copper pipe, I wonder if it somehow gets to the street transformer directly, in this case it provides almost as good current path as neutral.
    – gmygmy
    Commented Dec 11, 2017 at 22:50

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