ECN Forum Forums Code Related Discussion NEC & other Code issues Gas bond?'s

Yeah, Curt didn't think there was too much of a change to 2002, from '99 on this, but it is pretty significant is it not?

Has a footnote for a referance, wonder if that changed?
Ref: A-250-104(b)
National Fuel Gas Code, NFPA 54-1996

Took a few years to enforce it! As it seems to relax in 2002, I wonder what happens for 2005? Not that California will adopt it until 2007, if at all.

Only slight wording changes in '93, but same referance. Anyone have a copy of the National Fuel Gas Code, NFPA 54?

That was never the intention of NFPA 54 and is reflected in a formal interpretation of that section, that is why the NEC was changed back to the 1996 language.

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Charlie Eldridge, Indianapolis, Utility Power Guy

Quote: If the service nuetral opens, do you really want the gas piping to be at an elevated voltage, subjecting the gas workers to a shock?"

how would this be any diffrent for the plumbers working on the water main when the nutral was opened?

How would any elevated potential develop on grounded pipes? wouldn't the OCPD clear any faults? I would think an ungrounded gas pipe would be more dangerous to the gas man, if a hot wire gets laid on the piping, what would clear the fualt, assuming that the gas pipe is servicing a non-electrical appliance?

[This message has been edited by trekkie76 (edited 09-13-2004).]

You are correct and I wish we did not subject the water workers to this either.

There have been threads on the forums about water company's that do not allow the water pipe to be used a grounding electrode, they install a dielectric fitting before the meter and do not allow it to be jumped.

Then of course when a water pipe is separated the product that leaks out is not flammable. If there was current in the gas line when they break a union the resulting spark may not be welcome.


If the service neutral opens all grounded objects will be have an elevated potential to earth. This is particularly true if you have a plastic water main, as you will not be connected back to the source through your neighbor. This has nothing to do with the OCP.



Here IMO is where it gets cloudy, which is more likely? A bare hot wire contacting and remaining against a gas pipe or a service neutral opening.

It has been my experience that the service neutral opening is more common but my experience means nothing I would really be interested in facts and figures.

I also would ask again why the NEC used the words "may become energized" if they did not want some choice in the matter.

It would be simple for the NEC to state

"Gas Pipes Shall be bonded"

But they did not.

Anyone else have some input?

Bob

if the service nuetral opened with a properly installed EGC( made electrode or water pipe), what would happen if the nuetral opened? nothing, in theory. IMO the purpose of comprhensive grounding is to limit any possibility of potential forming between any mettalic pathways. I guess there are many scenerios that could be played out in this one. But isn't our job to anticipate the "what -if's" of life?

After fifeteen years of doing this, I have only counted the years, (So no stat's) but would say neutral drop out is more common than the one or two shorts I have seen clear on a gas line. However I have seen MANY shorts clear on water lines, as there are many more of them in any building. I guess it is that the gas be able to trip OCP, or MOCP rather than have it remain live, or worse cook off using the gas as an electrode. (However, the new high pressure lines here have a ground wire that PG&E bonds past the shut-off????)

My main gripe with it, is that it changed in '99 to "upstream from the shut off". (reflecting the same commentary in '93!) (We're on the '99, and probably will be until 2007, when we may or may not adopt 2005!)Making it simular to the change in '93 that moved the water to 5' from the entrance to the building. Making both a real pain... So in the '02 NEC it changes back. Why? Both '93 and '99 refferance National Fuel Gas Code, NFPA 54, (But doesn't in '02?)what is it that they are looking for, as it seems to me, that we are doing it for thier (the plumbers, etc.) benifit? Or ours, to clear OCP?

How do you figure this?

The only way that 'close to nothing' would happen is if the entire neighborhood has a common metal water system.

Many water mains are now plastic, the earth is not enough of a conductor to prevent the neutral from having a potential higher than the earth with a loose or open connection.

Open neutral, go to turn on the outside water bib to wash the car and you will be a conductor.


I agree but sometimes we need to know the most likely 'what if' that is why I said some facts and figures would be nice. We should not just do things based on are own experiences.

None this means anything if as you have to do what the AHJ expects in your area.

CharlieE has pointed out this.


I believe he is correct.

Bob

with a solidly grounded metal water pipe or made electrode system, wouldn't the effects of the service nuetral opening be minimized? the returns are all still grounded.

I assure you that an open service neutral is always a big problem for someone. It may be the premises that is being served or one of the adjacent properties but it will cause problems, it is the nature of the beast.

At the very least, the water piping system is not designed to carry the neutral current. After looking at the 800-ampere GEC for one service, the metallic water piping to the service on the next property that has a 100-ampere service and its GEC. I wonder about the voltage drop and ampacity of the circuit.