In my last code update course, the instructor, a local AHJ, got to talking about gas lines. In my area, most houses are equipped with gas water heaters, stoves, furnace, etc.
We got on the subject of bonding plumbing to the ground system and he stated that it would be a good idea to bond the gas lines in the house.
This strikes me as sort of a safety issue.
Looking at household plumbing, a bonding jumper is required at the water meter to prevent possible shock from an accidental current being carried by the plumbing pipes which are bonded to the grounding system of the service. If one carries this logic forward to the gas lines in the house, couldn't the same risk occur in the gas pipes?
Especially since gas lines are sealed at each joint with some sort of teflon tape or pipe dope which is almost certainly going to be a dielectric?
In my humble opinion, gas systems should be as far isolated from the electrical in a house as possible.
Does anyone diagree with this?

The pipe dope or tape is just a lubricant. That joint, made up gas tight, will have plenty of metal to metal contact.
250.104(B) seems to make bonding necessary if there is any electrical connections to gas fired equipment and inspectors might just say all pipes "may become energized".
Usually that will happen with the EGC of the equipment using line voltage so I never got to worried about it.
An example would be a furnace. The burner is screwed to the case which is bonded to the blower motor EGC and threaded to the gas pipe.

Should the idea that a gas meter can and sometimes is removed but we are not required to install bonding jumpers at the meter concern us?
How about replacing valves?
If there ever was a loss of ground at the service, there is always the possibility of the gas line and plumbing lines carrying current. As far as the water pipes are concerned, the only real danger here is getting a shock to ground. (signifacant but not catastrophic).
As for the gas line, breaking the joint while replacing a meter, valve, etc. may very well draw an arc which could potentially create a gas fire.
Maybe the code should include bonding jumpers at the gas meter as well as any valves in the system.
What do you think?

Installing a jumper across the meter would make the gas piping a grounding electrode, which is prohibited.

Not to use gas pipes as grounding electrodes is a measure against corrosion not against electric shock. Nowadays most gas pipes are polyethylene anyway.

Here bonding of internal gas pipework is mandatory as well as for any other metal pipework within a building.

Your gas pipe is usually bonded at the furnace, and the stove may have a plug on it there is another bond, gas pipe is not part of the grounding electrode syatem, just bond it, and replace the inspector.

In Gfretwells example: "An example would be a furnace. The burner is screwed to the case which is bonded to the blower motor EGC and threaded to the gas pipe." the gas pipes do get bonded. Interestingly, I had an inspector that made me remove a bond wire to a gas line. I asked him if he wanted me to isolate the pipes with plastic fittings and he just turned and left...

The purpose of bonding the gas pipes is the same as any other metalic piping bonded, becuase it is likely to be energised at some point in time.

However most gas appliances now days that have electronic igniters and/or controls, which means it should have an EGC which makes it a mute point to bond the gas pipe. But it does no harm and probable a left over from the days when people had gas heaters with pilot lite and fire place starters.

... Never bond a gas line... a NJ POCO employee was killed and the residence obliterated when a high impedence current leak was opened due to a routine gas meter change,and the arc of the act of disconnecting the meter ignited the gas in the pipe..it is unclear to me as per if the gas main shut-off was faulty,or not closed all the way,or there was gas left in the pipe ???... all I know is..the house exploded killing the worker,and from then on,it's been taboo to bond the gas main..
Russ

Just joined the forum recently, I have a couple of questions

Are the wiring regulations (codes ?) the same all over the US?

On the bonding issue- over here (UK) all gas pipes must be bonded within 600mm of pipe entry to house (on customers side of meter)

Each state can be different baldelectrician, such as here in California we just adopted the 2002 code, while other states are on the 2005 NEC.

Then each city in California may adopt local changes to the NEC.

Then ofcourse, each inspector has their own ideas of what is needed.

I have never bonded a gas line here in Southern California. I've been told The Gas Company doesn't want it.

AtticRat,
Can you cite a documented source for that? Gas in the pipe is way above UEL (upper explosive limit) and will not burn. Yes, it is very possible to ignite the gas as it escapes from the pipe, but that would not cause an explosion and I would not expect serious injuries...maybe burns, and yes if the gas is not shut off the building may burn down.
How do you isolate the gas line? It will have a connection back to the electrical system from the gas/electric equipment that the gas line feeds.
Don

I have worked on a number of residential furnaces where there was no solid connection between the burner assembly and the furnace itself. The burner assembly just sits in brackets, without screws or other mechanical bonding. In this type of equipment the furnace EGC, does not provide a good bond to the gas piping.
Don

In Germany similar to the Uk bonding on the client's side is mandatory as defective electric equipment connected to the gas pipe anywhere in the building could transport dangerous voltage. If ungrounded this cannot be detected properly.

The incoming gas pipe in front of the meter must now have a piece of electrically isolating plastic. This is to prevent 1. corrosion and 2.import of external voltages from the neighboured house for example. Gas pipes other than old water pipes are usually covered with isolating anti corrosion material and so do not have a low ground resistance. (New water or gas pipes now are always in PE outside of a building anyway)

As plastic pipes within a building would be an important fire risk and prohibited, imho it will be impossible to isolate the electrical part of gas equipment from gas transporting part as lamplighter has proposed.

... No Don, sorry, This was told to me by an instructor at one of my CEU classes... maybe an urban legend,and he wanted to shake us up a bit so we wouldn't do it.???
If it's not true,and that sort of explosion can't happen,I don't want to perpetuate the myth..You'd know better than me..
Russ

Where I'm at... Pre-2001 CEC ( '99 NEC with Changes) we bonded gas at the water heater usually. Hot cold and gas.... It was a typical check list item....

Then the '99 NEC was adopted as the 2001 CEC, and a few things changed... (Oh, can anyone tell me what that "x" is for?)

Then we had to bond gas to the service GEC from just past the meter, without it being between the electrodes...

Now we just started doing it on the new 2004 CEC (2002 NEC with changes)

Now I don't know what to make of it... If you're coming from a sub-panel for the circuits for Furnace or other gas appliances, you would then have to bond the gas to the main? Do we go back to the water-heater method? Bond anywhere to water? (As the cold water is always a GEC here.) Or stick to the real PITA '99 NEC method of back to the Main GEC? (At the gas meter from the service, which can be on opposite sides of the house.)

Only time will tell...
FYI I'm still being asked for the PITA '99 method lately.... Although it seems clear to me that its no longer nessesary.


[This message has been edited by e57 (edited 10-26-2005).]

NORCAL

Mark(E57), that small "x" "...indicates that material has been extracted from other NFPA codes and standards. The source documents are identified in Appendix A."

Edit - Appendix A states A-250-104(b) is from the National Fuel Gas Code, NFPA 54-1996.

steve

[This message has been edited by stamcon (edited 10-26-2005).]

I just finished my code update class today and gas pipes were ofcourse a topic.
According to Art. 250.104(b), as several of you have stated, the gas pipe is required to be bonded, however, the equipment grounding conductor can be used for this purpose.
According to my instructor,(a local AHJ), the gas pipe need not be bonded with any bonding jumpers since the E.G.C. is allowed to act as the bond itself.
According to him, the E.G.C. meets the requirements of the code and no further bond is needed.

I can see both sides of the issue here. It's sorta like fueling an airplane, you touch the clamp from the fuel truck chassis to the airplane metal before you let fuel flow. Electrolysis is an issue with metal pipe in the ground and no sleaving so you might not want it grounded. For safety in the house, it probably makes sense to ground it. All I know for sure is that I wouldn't touch the meter without bonding around it first, to make sure I would get any sparks because of a potential difference.

According to Art. 250.104(b), as several of you have stated, the gas pipe is required to be bonded, however, the equipment grounding conductor can be used for this purpose.


That is how I've always understood it. Whether the furnace/ boiler is wired in E.M.T. or MC cable, the EGC is sufficient to bond the gas piping in the house.

In BC, we must bond the gas line.

A few years back I was installing a service on a new mobile home. The gas company had installed their line (metal) from the street, and capped it off without a meter. The gas installer hadn't yet run the pipe out from the furnace. Rather than making a 2nd trip back to bond the inside gas line, I decided to bond the incoming line from the street....ended up getting an irate call from a foreman at the gas company saying it was a big NO NO to bond their line as they run a small current through their old metal lines for corrosion. The meter has an isolation point so by bonding on the "load" side of the gas meter, the bond is isolated from the "line" side.