gas line bonding/grounding

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abe

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Hi
gas company has been called to turn on the meter of an apartment in a 17 unit apartment building. They claim there is 9 volts on gas line and they will not connect the gas. what should be done? bonding to cold water and metal part of electrical meters solve it? Thanks
 
abe said:
Hi
gas company has been called to turn on the meter of an apartment in a 17 unit apartment building. They claim there is 9 volts on gas line and they will not connect the gas. what should be done? bonding to cold water and metal part of electrical meters solve it? Thanks
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Find the source of voltage. It may also exist on the water piping, as well as the equipment grounding conductors even if they are all bonded together. I ask gas tech exactly where, what, how he measured voltage.
 
Section 250.104(B) requires bonding metal piping systems other than water piping systems. That includes gas.
 
abe said:
Hi
gas company has been called to turn on the meter of an apartment in a 17 unit apartment building. They claim there is 9 volts on gas line and they will not connect the gas. what should be done? bonding to cold water and metal part of electrical meters solve it? Thanks
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Rewire the complex for all electric heat and appliances. That'll fix 'em.

kwired said:
..... ask gas tech exactly where, what, how he measured voltage.
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This is probably a more workable course of action, and is what I would do. I would also talk to someone higher up at the gas company before I did any extra work.
 
Look at NEC 250.52(B). You cannot use metal underground gas piping systems as a grounding electrode. So if you bond it then it will become a grounding electrode. But if there is an insulating coupling inside the meter then you could bond on the premises side of the coupling.
 
stickboy1375 said:
No it won't. :) It just becomes a piece of metal that is bonded to an electrical service.
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If that piece of metal is electrically continuous to the earth it will act as an electrode and is therefore a violation even though it wasn't anyone's intention that a gas pipe should be an electrode.
 
There should be an insulating coupling inside the gas meter that electrically isolates the interior gas pipe from the earth. You must bond on the premises side of that coupling. If you bond on the utility side it will become an electrode and therefore a violation.:happyno:
 
Now for a shot of reality. Few years back I was involved in rennovations because of a fire in a kitchen on a farm house.

Fire started when lightning struck power pole only 30 - 50 feet from house. Followed service drop to house, through service equipment, through bare neutral of an SE cable running to an electric range outlet. The installed range was gas range using LP gas supplied by copper tubing under the house and out to a tank in the yard. Best we can tell lightning arced from electric range outlet to the gas pipe. The fire definately started behind the range and right after that lightning strike. If that gas piping had an insulating fitting why would that have stopped this event when the gap from the outlet to the pipe would have been much farther than an insulating fitting would have provided?

BTW there was no installed grounding electrode at the service so this was next best thing. No guarantee it would have stopped this event but couldn't have hurt anything. We did install grounding electrode as part of the repairs.
 
^^^^You say that there was a gas tank in the yard? That means the gas was not coming directly from the gas company but was being stored in the tank instead. Why would there be a gas meter if the owner already has a storage tank for his gas?

The rules of the NEC are very clear about underground gas piping. You cannot use it as an electrode. The only way to bond an interior gas pipe and keep the underground portion of the pipe from developing stray voltage and electrolysis is to have an insulating coupling close to where it enters the building.
 
erickench said:
There should be an insulating coupling inside the gas meter that electrically isolates the interior gas pipe from the earth. You must bond on the premises side of that coupling. If you bond on the utility side it will become an electrode and therefore a violation.:happyno:
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Where does the violation come into play? As far as I can read, I can't use the gas pipe AS a grounding electrode, but where is the violation if I choose to bond it voluntary or involuntary?


My point being, if the plumber uses CSST type gas pipe, then I have to bond the gas piping... simple as pie in my opinion.. You are confusing the wording of the NEC, it simply states that you cannot use the gas pipe as a GEC... but if it gets bonded anyway... o'well.
 
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My point being, if the plumber uses CSST type gas pipe, then I have to bond the gas piping... simple as pie in my opinion.. You are confusing the wording of the NEC, it simply states that you cannot use the gas pipe as a GEC... but if it gets bonded anyway... o'well.
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If it gets bonded then it has the same effect of using it as an electrode because the pipe is in contact with the earth. That's why we have the insulating coupling. This thread started because a gas company detected stray voltage on it's gas pipe. Somebody bonded the pipe on the utility side of the meter.
 
erickench said:
^^^^You say that there was a gas tank in the yard? That means the gas was not coming directly from the gas company but was being stored in the tank instead. Why would there be a gas meter if the owner already has a storage tank for his gas?

The rules of the NEC are very clear about underground gas piping. You cannot use it as an electrode. The only way to bond an interior gas pipe and keep the underground portion of the pipe from developing stray voltage and electrolysis is to have an insulating coupling close to where it enters the building.
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This pipe was not intentionally being used as an electrode. The incident happened anyway. I never said anything about a meter. Part of my point here is with that kind of voltage seeking a path to earth a dielectric union is not going to stop it. Use of electrodes that are lower resistance to ground than the gas piping is how you divert (but not necessarily eliminate) current away from the gas piping.

You are still required to bond to gas piping. Gas piping inherently is bonded via equipment grounding conductors to any gas appliances and any other contact with grounded objects anyway. If the piping has no dielectric fitting it will naturally be an electrode to some degree whether you like it or not.
 
kwired said:
Part of my point here is with that kind of voltage seeking a path to earth a dielectric union is not going to stop it.
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A dielectric union as you call it will prevent electrolysis. This is what the gas company is concerned about. Here is the NEC rule again:

250.52(B) Not Permitted for Use as Grounding Electrodes.
The following systems and materials shall not be used as grounding electrodes:
(1) Metal underground piping systems
(2) Aluminum

I happen to know that the water companies have the same complaint about using their pipes as electrodes because of electrolysis. Imagine if a gas or water pipe were to become corroded and spring a leak as a result.
 
erickench said:
A dielectric union as you call it will prevent electrolysis. This is what the gas company is concerned about. Here is the NEC rule again:

250.52(B) Not Permitted for Use as Grounding Electrodes.
The following systems and materials shall not be used as grounding electrodes:
(1) Metal underground piping systems
(2) Aluminum

I happen to know that the water companies have the same complaint about using their pipes as electrodes because of electrolysis. Imagine if a gas or water pipe were to become corroded and spring a leak as a result.
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Electrolysis is not going to happen with AC current. If you have an electrolysis problem it is coming from a DC source. Checking out telephone lines may be a place to start.

I am well aware of 250.52(B). I am saying that means don't run a conductor sized to 250.66 to the gas piping with the intent of calling it a grounding electrode. It inherently becomes an electrode to some extent anyway if it is a metal object in contact with earth.

Water companies can complain all they want about current on the lines - it will happen anyway which is one reason why NEC wants metal water piping to be used as grounding electrode if it is present. Water piping will usually have lower resistance than any made electrodes - that is just the way they naturally are.
 
^^^^ And what about stray voltage on the gas company's pipeline? Apparently they consider it to be a problem otherwise they wouldn't refuse to turn on the gas.
 
erickench said:
^^^^ And what about stray voltage on the gas company's pipeline? Apparently they consider it to be a problem otherwise they wouldn't refuse to turn on the gas.
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Gas companies pipeline or customers site piping?

If they had no dielectric fitting they would not measure any voltage across any such fitting. That said it is not desired to have current flowing through their system anyway but all the tech did was measure voltage. We know very little beyond that. If gas supply system has dielectric fittings at each service, the problem is likely coming from the users side. For all we know so far the cause of the problem could exist at a neighbors house and was simply observed where this action took place.
 
I do not see the gas company complaining about stray voltage on the premises side because the piping is the property of the owner and not the gas company. If there is no dielectric coupling then the gas company should immediately install one.
 
erickench said:
I do not see the gas company complaining about stray voltage on the premises side because the piping is the property of the owner and not the gas company. If there is no dielectric coupling then the gas company should immediately install one.
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In general, where is the stray voltage going to come from on the utility side? The premises side is what will be connected to electrical systems whether intentionally connected or not, the utility side will be in contact with earth and will be at earth potential. If they have dielectric couplings at every service then they are isolated even more from possible energization of their lines.
 
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