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#101034 - 02/03/07 09:00 AM New gas pipe requirements
Alan Nadon Offline
Member

Registered: 03/10/05
Posts: 398
Loc: Elkhart, IN. USA
Flexible coated gas piping (CSST)? is being used in homes. It is spiral steel tubing with a Nonmetallic jacket. Usually yellow. 250.104 NEC requires piping that may become energized to be bonded. A gas appliance with a 20 amp circuit gets bonded with the ground wire in the circuit (250.66).
The flexible gas piping is failing in some areas due to lightning. The pipe manufacturer requires it to be bonded with the same size GEC as used for the service (250.122 NEC) The bond must also be on the Black iron pipe part of the system or at one of the connectors for the tubing. Never on the tubing.
It seems like the installers & makers of the flexible gas pipe are shifting the responsibility for their product onto the electrician to protect it against lightning, something the electrical code isn't designed to do.
What do you think about this ?
Alan--
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Alan--
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#101035 - 02/03/07 09:14 AM Re: New gas pipe requirements
George Little Offline
Member

Registered: 01/18/04
Posts: 1492
Loc: Michigan USA
I can see it now- a 3/0 bonding conductor fastened to a 1/2 inch gas line :-)
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#101036 - 02/03/07 09:31 AM Re: New gas pipe requirements
yanici Offline
Member

Registered: 09/03/06
Posts: 57
Loc: Atlantis
What do you think about this ?
Alan--

Alan, it seems to me that this type gas piping needs to be outlawed. I never did like it. Just because you increase the EGC size at the iron pipe joint doesn't eliminate ground current on the flex pipe. Next thing you know we'll have to run a green bonding jumper along the length of flex-pipe.

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#101037 - 02/03/07 09:34 AM Re: New gas pipe requirements
earlydean Offline
Member

Registered: 12/22/03
Posts: 749
Loc: Griswold, CT, USA
We have had this question in CT, as well. It has been fueled by a very confusing letter from the manufacturer to every town's building department.

Our official response has been to ignore it. All gas appliances are bonded by the EGC, and thereby the flexible gas pipe as well. Isolated portions of this gas piping are not likely to be energized, and therefore do not require bonding [250.104(B)].
The NEC does not allow the gas piping to be used as a grounding electrode, so where it comes out of the earth is never bonded anyway [250.52(B)(1)], and the gas code requires an insulating fitting where it comes out of the ground.

What I do not understand is how this pipe is "failing due to lighting". A lightning strike is seeking an earth ground. If the service conductors are bonded properly at the service, then there is no way the lightning could make it into the house along the branch circuit conductors, through the appliance, ignore the equipment grounding connection, and follow the gas pipe back through an insulating fitting at the gas meter. Electricity takes every path presented to it, but in this case there is not a path presented through the gas pipe.

My guess is this piping is so thin it is actually failing due to contaminants in the gas delivered, not lightning strikes.
_________________________
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#101038 - 02/04/07 06:33 AM Re: New gas pipe requirements
jes Offline
Member

Registered: 07/12/02
Posts: 103
Loc: CT
Folks, this piping is indeed failing due to lightning sideflash within structures. The flash may be between piping or wiring to this tubing and arcs a small hole through it resulting in a gas leak. The 'good' leaks (if you will) are ignited by the arc and call attention to themselves. A 'BAD' leak does not ignite and I have heard reports of subsequent explosions. It is a real problem. I am not sure that the recommended bonding will solve the problem however as I have seen cases where it was solidly bonded and still failed as described above. Earlydean, I was at two of these in CT last summer.

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#101039 - 02/04/07 09:35 AM Re: New gas pipe requirements
earlydean Offline
Member

Registered: 12/22/03
Posts: 749
Loc: Griswold, CT, USA
Please tell me how this is consistent with electrical theory.

Where is the complete path the lightning would take?

If bonding is done per code, it is beyond my understanding how it could be caused by lightning.

(And how is it these did not make the newspapers here in CT? or did I just not notice? Do you recall the dates and the towns?)

Please enlighten me.
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Earl

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#101040 - 02/04/07 10:43 AM Re: New gas pipe requirements
yanici Offline
Member

Registered: 09/03/06
Posts: 57
Loc: Atlantis
Here's an articl from the Charleston Regional Business Journal. http://www.charlestonbusiness.com/pub/13_1/news/8415-1.html
Interesting reading.

Also found a class action suit.http://www.pddocs.com/csst/faq.aspx#Q23

While Googling around I read that the lawsuit has been settled and the gas pipe manufacturers are allowing X amount of $$ to bond your gas service and install lightning protection. If you live in a place of high incidence of lightning you get more $ to do your electrical work.

Has anyone done any of this work yet? What size bond are we talking about? I read on one plumbers site that a #6 copper was needed. It also said that an electrical permit was needed when this type piping was to be installed as new work or remodel. I'm just a little concerned that ground fault current or accidental neutral current might flow on the gas service pipe and cause fire or even explosion.
[This message has been edited by yanici (edited 02-04-2007).]

[This message has been edited by yanici (edited 02-05-2007).]

[This message has been edited by yanici (edited 02-05-2007).]

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#101041 - 02/06/07 07:58 AM Re: New gas pipe requirements
SolarPowered Offline
Member

Registered: 07/05/04
Posts: 615
Loc: Palo Alto, CA, USA
I don't understand.

If you bond the CSST, does it not become a better ground path for the lightning, thereby increasing the likelihood of this sort of lightning-induced punctures?

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#101042 - 02/06/07 10:01 AM Re: New gas pipe requirements
mikesh Offline
Member

Registered: 06/07/06
Posts: 614
Loc: Victoria, BC, Canada
Here is a little history from Canada re bonding of Gas pipes. It was considered acceptable to allow the branch circuit bonding (EG) conductor to do the job. For example the gas furnace fan motor is a #14 with a #14 bond. Now enter a lightning strike and the bond conductor burns off and the voltage is high enough to damage the motor insulation causing leakage to ground. Since the bonding conductor is now burned off the O/C device does not trip and someone steps on a heat register and a grounded surface and gets shocked or worse. This did not just happen once, but enough to cause a change which requires a minimum #6 bonding conductor to the gas pipe.
So a little about lightning. Lightning follows the path of least impedance not lowest resistance. This is not necessarily along the copper ground wire but can jump from a lightning rod to a heat duct to a water line and into the building steel. the energy from a lightning strike has to dissipate and can travel horizontaly over a wide area around the ground strike. It can just as easily follow a gas pipe into the house and cause havok to the interior wiring. In my jurisdiction the gas piping is plastic in the ground and the meter has an isolated section too.

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#101043 - 02/06/07 12:35 PM Re: New gas pipe requirements
earlydean Offline
Member

Registered: 12/22/03
Posts: 749
Loc: Griswold, CT, USA
I got a telephone call from the electrical inspector involved with both of those CT lightning strikes. They did not make the papers, but they were very real, he says. The bonding was done per code, and the damage was definately due to lightning. He described the arc burns on the building. Wow!!
I believe him, as he is a respectable inspector and was a local electrical contractor for years. He delivers seminars in CT on electrical code. Very knowledgable.

I wonder how bonding the connections to the black iron is going to solve this problem???
_________________________
Earl

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