Bonding of gas piping

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JJWalecka

JJWalecka

Senior Member
Location
New England
Article 250.104B states
Quote:
(B) Other Metal Piping, Where installed in or attached to abuilding or structure, metal piping system(s), including gas piping, that may become energized shall be bonded to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor where of sufficient size, or to the one or more grounding electrodes used...

Wouldn't all gas pipe have the potential to become energized? If I bond the structural steel would the gas pipe ,supported by metal hangers and fasteners, be adequate? Is it best to bond the gas pipe or is it something that is rarley enforced. I guess that it is best to have all metal to have the same potential to earth. Thank you for your time and effort.

Justin
 
Re: Bonding of gas piping

(B) You left out this part "The bonding jumper(s) shall be sized in accordance with 250.122 using the rating of the circuit that may energize the piping system(s). The equipment grounding conductor for the circuit that may energize the piping shall be permitted to serve as the bonding means. The points of attachment of the bonding jumper(s) shall be accessible."


This was a mess in the 1999 Code.

IMO if an appliance is connected to the gas and connected to the electrical system the equipment grounding conductor of the branch circuit supplying that appliance will provide the connection required by 250.104

Charlie
 
Re: Bonding of gas piping

Charlie,

Thank you. I was thinking more in the lines of a large commercial installation like a Lowes Hardware or Home Depot. The gas pipe would be for roof top units and such. Chances are that it doesn't spec it in the print but is it right to bond it? Thank you.

Justin
 
Re: Bonding of gas piping

I believe the intent is as stated in 250.104 that may become energized. I agree that the statement is ambiguous. But I do not consider such piping to fall under this provision if the piping supplies non energized (electrically)equipment.

From a practical point of view the odds are the gas eq will utilize electricity also and in that case I would consider the installation bonded by the EGC of the circuit supplying the appliance.

Are these units you have in mind isolated in some way that the branch circuit EGC would not be case bonded to a metal Gas Pipe??

Charlie
 
Re: Bonding of gas piping

Charlie,
The units themselves would be grounded through the branch circuit grounding conductor feed to the disconnect on the roof. In theory ,I guess, the gas pipe would be grounded through that. I wasn't sure if you would treat the gas pipe like you would the water pipe (bond the street and load side of the meter) and sprinkler system.

Justin
 
Re: Bonding of gas piping

No I would not bond the gas pipe at the street if you did, what size wire would you use??

The direction I think you are going in is exactly why the language in this section (in the 1999 NEC) was reverted back to the 1996 250-80 b language (bonding by the branch circuit EGC) for the 2002 cycle. I don't have the 02 ROP or ROC available right now but it was a literal blood bath. I'm very confident in my opinion regarding this existing language.

Charlie
 
Re: Bonding of gas piping

If the appliance is disconnected from the circuit then the logic would imply that the pipe is not likely to become energized??

Charlie
 
Re: Bonding of gas piping

But the equipment would be de energized so the pipping would not likely become energized
 
Re: Bonding of gas piping

Last time I bonded a gas line, I ran a #12 solid to it and grounded it. Only had a 20A breaker feeding the gas fired heater and the #12 satisfied the coad and the inspector. I just had to protect the wire with some 1/2" PVC.
 
Re: Bonding of gas piping

my understanding of the dilemma is that the CSST industry helped push for an interp that allows for a cord and plug interp of the code. If you read the definition of bonding in art 100, "permanent" is used to describe connection. A cord and plug attached to a duplex receptacle is not a permanent connection.

I seem to be in the minority on this and am tired of the same argument over and over and over again. i believe that the bonding conection can utilize the egc, BUT the connecting means must be a listed connector for bonding, not the grounding tang of a cord, which is listed for grounding.

I believe that the exception for this metal piping system is the only exception (for bonding) for metallic pipe within a residence, and it is the one system that should be bonded especially where there are chances of arcing with near lightning strikes. If both ends are bonded, there is a very much lessened chance of arcing, and arcing has been linked to CSST failure.

Anyway, i am in the minority, it seems, and am unwilling to persue this argument any further than stating my opinion. I probably typed a couple of thousand words on another site about this issue, so enough.

post the topic in the grounding and bonding section for more diverse opinions

paul
 
Re: Bonding of gas piping

Paul: I have a hard time visualizing the need to bond CSST. 250.104 says that we need only bond gas piping "where likely to become energized". I don't see how CSST becomes energized, since it is insulated. On the other hand, I know this is a pet peeve of yours, so perhaps you can shed some light on it.

Thanks
 
Re: Bonding of gas piping

Ryan: you and I disagree on the meaning of likely to become energized. That is an inherant part of our disagreement. Any metallic system in a house is or can be energized where passing thru or in spaces occupied by wiring. This is not clearly spelled out for either position in the NEC. The NEC says where the appliance is energized, it may be grounded by the EGC. It does not say the grounding tang of a cord is acceptable

Gas piping is exposed and contact with other metallic systems where it enters the house. It also passes thru walls, studs, floors and may be inadvertantly energized just as other metallic systems may be.

My pet bugaboo came about when there were reports of CSST failure in near lightning strikes. This was a few years ago and when I brought it up on the ICC site, one of the most articulate heavy hitters from the industry (CSST industry) replied extensively to the issue. After reading all of his posts, he was only saying that it was legal given the code. he never answered any of the problems brought up.

i am only interested in the issue as gas and electrical power are the two greatest causes of destroyed homes from non-cataclysmic events. Gas and Electric kill people. The NEC is theoretically about aving lives, not providing neat looking wiring jobs. The same should be true of gas installs.

The issue as I see it is that CSST is allowed to do what is/was disallowed in the mechanical code, passing corrugated piping thru walls and cabinet spaces. It is also not bonded permanently by any methods mentioned in the NEC. The problem is that this required special fittings and no one was using them.

It is also not bonded at both ends and this leaves a metallic system possibly with enough potential difference, end to end, to arc. Arcing was found to cause CSST failure. Arcing failure was found to exist with near lightning strikes. This wouldn't be a problem with a rigid piping system that required a more direct lightning strike.

When I initially brought up these questions in relation to questions raised by others, the questions weren't answered, I was just continually put down. One might win the contest by how well this is done, but the questions have not been answered. All I wanted was the questions answered, not informed where the code citation existed, which I had now read about thirty times.

The industry may have changed since then, and the use of real bonding fittings may have become more prevalent, and other inspectors may see things the way I do, but I am not about to make a big deal about it anymore. This was about the same time that AFCI's were being touted as god's gift to save the lives of the poor hapless and helpless bedroom dwelling victims of poor electric work. I didn't believe that either. I was also told that that was a fait acompli, a done deal forever and ever.

You asked.

paul
:)
 
Re: Bonding of gas piping

Ok if an installer takes the time to route wiring in a manner that there is no crossing of gas piping then yes there is no actual chance of being energized ;) Who here has actually seen this ;)
 
Re: Bonding of gas piping

I think what Paul is describing is the magnetic flux from a close by lightning strike that can impose a high current on metal that is not bonded. H'mmm I think lightning can still impose a current on any metal even if it is bonded. Remember magnetic flux is isolating and does not have a reference to Earth or anything else. It is a current that is developed within the core of the metal that is being imposed upon, weather this be the core of a transformer or a gas pipe. Bonding will have no more effect to reducing this current than the X/O bonding of a SDS transformer. the current will still be there and any weak links in the gas pipe can rupture. and the fact that lightning has too many variables to even get close as to where the other end of this core will be to shunt it out also? Even with the common frequency of 10 meghz that is expected of most lightning strikes. What would be the impedance of this gas pipe from one end to the other at that frequency? I think you would have better luck forecasting the weather.
I don't think the NEC is trying to protect against lightning strikes. It would seem to me the NEC is more trying to protect the gas pipe from being energized by a circuit that might likely energize it. which would be a circuit that supply's equipment that also uses gas? Which the EGC of this circuit is more than capable of doing this.

Just my thoughts? ;)
 
Re: Bonding of gas piping

I think the lightning issue is jousting at windmills. If a circuit is likely to energize the gas piping system, it has to be in contact with gas piping system. In other words, the circuit that feeds an appliance like a gas furnace will also be required to ground it. Nothing else needs to be done. :D
 
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