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The gas company technician has turned gas off to the gas meter because he detected .4 volts coming off the gas pipe leading to our furnace. The meter was disconnected when he tested the pipe. He stuck a screw driver in the soil to use as a ground and then put the multi meters red lead on the pipe to show .4 volts. However, when tested at the furnace using its ground there is no voltage at all on his multimeter. Any ideas on what the discrepancy is caused by? I have done my own tests at multiple different properties and consistently get .3-.6 volts on gas meters using a Fluke 117. So, is this normal?

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  • A 6" screwdriver stuck into the dirt seems like an odd way to do a test that you having gas service depends on. I think your question should focus on finding where that voltage could come from.
    – JPhi1618
    Nov 13, 2017 at 21:22
  • Is this a DC or an AC voltage?
    – ThreePhaseEel
    Nov 13, 2017 at 23:19
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    I can stick my fluke in the ground and put it next to a hot wire and get more voltage than .4 this is total B.S. If you have metal pipe and it is in contact with earth for 10' you really can't get any better than that but code requires the gas line to be bonded to the electrode system if likely to be energised. I would call and complain because a screwdriver is not a ground rod and may have turned the meter into an antenna.
    – Ed Beal
    Nov 13, 2017 at 23:22
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    The dirt is NOT ground (at least not from an electrical perspective). Call the gas company and complain. Hopefully you got the guys name, so you can report him. If the gas pipe is bonded to the electrical ground at the furnace, then the piping should be at the same potential as the electrical ground system. It also means that if there is an electrical fault to the pipe, the fault can be cleared by the furnaces grounding conductor. I've been digging through National Fuel Gas Code, and I can't find anything that requires the gas pipe to be at the same voltage potential as a pile of dirt
    – Tester101
    Nov 14, 2017 at 11:51

3 Answers 3

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I agree with Ed Beal. The technician had no idea what they were doing.

The gas pipe is required to be bonded yes, but the equipment ground that serves the electrical circuit for the furnace is allowed to be the sole means of that bonding.

From the 2017 National Electrical Code (also in earlier versions)

250.104

(B) Other Metal Piping. If installed in or attached to a building or structure, a metal piping system(s), including gas piping, that is likely to become energized shall be bonded to any of the following:

(1) Equipment grounding conductor for the circuit that is likely to energize the piping system. ...

You said --

However, when tested at the furnace using its ground there is no voltage at all on his multimeter.

This tells me your equipment grounding conductor for the gas furnace circuit is in good condition.

A millivolt signal to a screwdriver stuck in the ground is not a reliable way to do earth ground testing.

The Utility should immediately restore your service and that technician needs to be properly trained.

Good luck!

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  • On the initial visit I had my electrician onsite with the tech. After he showed the tech how to use the meter the field supervisor told the electrician he could bond the meter to the panel to address the "issue". The next "senior" tech refused to touch the meter because it was bonded to the panel. Which he said should never be done. I think he was confused. I can only imagine he thought it was being used as a ground for something else. So, I had the electrician remove the bonding ground wire. I have spent of $500 so far. The senior tech would not give me the supers contact info, only 800 #
    – Nick
    Nov 14, 2017 at 13:46
  • @Nick In some places, the gas company "energizes" the underground metallic piping with a DC voltage to prevent corrosion (impressed current cathodic protection). The outlets on the meter have a coupling that electrically isolates the service (gas company) side piping and meter, from the supply (home) side piping. If you place a bonding jumper across the meter, you're effectively removing this intentional isolation. Because of the isolation, the gas piping in your home is electrically "floating". This is why the code only requires you to bond it, if "is likely to become energized".
    – Tester101
    Nov 14, 2017 at 14:47
  • They may also put a trickle voltage on the piping to aid in broken pipe detection. You deserve a full refund of any money spent.
    – ArchonOSX
    Nov 14, 2017 at 16:50
  • Tester 101 is correct. The applied voltage for corrosion protection is more negative than minus 0.8 V.
    – blacksmith37
    Nov 14, 2017 at 17:10
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This is completely wrong! The screw driver is not a proper ground rod.

I think the proper grounding is at least 8 feet for a ground rod. It is possible also that some ground rods are no longer at 'ground' potential which is why they can get replaced every now and again - so people can get a bad reading. Typically this is checked with a megger. I said that to say this - did he check his screwdriver with a megger to make sure it was correctly at ground?

NEC 250.52(A)(5) states: “Rods and pipe electrodes shall not be less than 2.44 m (8 ft.) in length.” ... With regard to diameter requirements, NEC 250.52(A) (5)(b) states, “Grounding electrodes of stainless steel and copper or zinc coated steel shall be at least 15.87 mm (5/8 in.)

So considering that - does the Gas Technicians Screw Driver match those requirements ?

If he had a 5/8 inch diameter screw driver eight feet long plus handle that he drove into the ground then he is right; otherwise, as others have said call the gas company back out and have them send someone else.

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  • Even if the guy pounded in an 8' copper ground rod, there's still no reason to expect the dirt to be at the same voltage potential as the electrical grounding system.
    – Tester101
    Nov 14, 2017 at 12:05
  • Thanks for all the helpful posts. I agree with all of your assessments. I've had three separate techs out here. Once they see the note on the account that there was voltage on the meter, they require me to show them proof of a fix by a professional. The initial tech reported he measured 400 volts. I had my electrician meet him onsite immediately. Turns out he had .400 or .4 volts. So, my account shows that the meter had 400 volts on the meter when it never did. I've explained to them that 2 different electricians have deemed it to be safe. I'll bring this thread to my next attempt. Tks
    – Nick
    Nov 14, 2017 at 13:39
  • @Nick if your electrician met him onsite immediately - get a written statement from your electrician stating that the gas tech failed to properly read his meter and the actual reading was .4 volts but used a screw driver as a ground rod which is not code acceptable for measuring anything.
    – Ken
    Nov 16, 2017 at 0:38
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Yes, I think the gas company tech is completely out of his league. Additionally, he is trying to enforce a testing program designed by someone just as far out of his element. 4/10 of a volt wouldn't even qualify as phantom voltage much less intrinsically safe voltage. You can walk across dry carpet and produce more than that. I hate to say it but you need a lawyer. The utility company is required by law to supply you with gas as long as you pay your bill and your system does not present a hazard to yourself, your neighbors or the utility itself. Good Luck. P.

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  • Walking across carpet, you can build up tens of thousands of volts. Does that mean the 120 volts in your house is not dangerous?
    – Tester101
    Nov 14, 2017 at 12:09

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