correct me if i am wrong but in 250.2 under ground-fault current path under the fpn, it shows a combination of different metals used for a good path. In reading further i see they state gas piping as one of the metals. I was always taught that this would be very dangerous and to me gas pipe would not be a good choice for a ground, or am i just understanding this wrong?
grounding
- Thread starter rjdad82
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bphgravity
Senior Member
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- Florida
Re: grounding
I don't see anything in that FPN or defintion that is suggesting that gas piping is a "good" ground-fault path. This definition only defines all that could be a path of fault current. Metallic gas piping certainly would qualify. By establishing an Effective Ground-Fault path, the hazard and dangers of gas pipe being used as a ground fault path are reduced.
I don't see anything in that FPN or defintion that is suggesting that gas piping is a "good" ground-fault path. This definition only defines all that could be a path of fault current. Metallic gas piping certainly would qualify. By establishing an Effective Ground-Fault path, the hazard and dangers of gas pipe being used as a ground fault path are reduced.
Re: grounding
Bryan, you're right, there is nothing "suggesting" at all about it, it is simply a fact that metalic gas piping is a good conductive path when used for; grounding, bonding, or what have you.
Roger
[ October 11, 2004, 09:46 PM: Message edited by: roger ]
Bryan, you're right, there is nothing "suggesting" at all about it, it is simply a fact that metalic gas piping is a good conductive path when used for; grounding, bonding, or what have you.
Roger
[ October 11, 2004, 09:46 PM: Message edited by: roger ]
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: grounding
I know there are many that when they think of a electrical connection to a gas pipe. But you must know this. Gas will not ignite as long as there is no accelerator (oxygen) in the line.
The problem happens when the pipe is broken or taken apart. Then this is only a problem if there is current on the pipe. (which there should not be any) This is why most gas company's have gone to using plastic tubing, as this eliminates this problem at the meter. Which is also why gas pipe cannot be used as part of the grounding electrode system.
The only requirement in the NEC is to bond it when it is likely to become energized (250.104(B) which also allows the EGC serving the equipment that might energize the gas pipe to be used as this mean's of bond.
In general wiring installed to code will not pose as a source to energize the gas pipe. so this only leaves the equipment that uses electricity and gas as the source that might energize the gas pipe.
[ October 12, 2004, 01:38 AM: Message edited by: hurk27 ]
I know there are many that
when they think of a electrical connection to a gas pipe. But you must know this. Gas will not ignite as long as there is no accelerator (oxygen) in the line.The problem happens when the pipe is broken or taken apart. Then this is only a problem if there is current on the pipe. (which there should not be any) This is why most gas company's have gone to using plastic tubing, as this eliminates this problem at the meter. Which is also why gas pipe cannot be used as part of the grounding electrode system.
The only requirement in the NEC is to bond it when it is likely to become energized (250.104(B) which also allows the EGC serving the equipment that might energize the gas pipe to be used as this mean's of bond.
In general wiring installed to code will not pose as a source to energize the gas pipe. so this only leaves the equipment that uses electricity and gas as the source that might energize the gas pipe.
[ October 12, 2004, 01:38 AM: Message edited by: hurk27 ]
Re: grounding
Hello-
Hope this sheds some light on the situation. Any metallic or conductive material that may become energized inside a building or facility must be bonded together for safety reasons.
Underground metal gas pipes are not permitted for grounding as per 205.52(B)(1) This is where your original safety concerns probably came from.
250.2 and 250.104(B) refer to above ground piping on the customers side of the gas meter.
Underground gas systems are required to have an isolation bushing installed preventing any electrical interconnection between the primary side and the secondary side of the gas meter. In the event of a fault current, this bushing prevents the underground piping from acting as a grounding electrode.
Sometimes there is a small amount of DC present on an AC system. This DC has been responsible for several pipeline explosions by burning pinholes through the metal. (This is the same concept used in electroplating- transferring metal using a direct current) Small amounts of AC current are common on most grounding systems and can be measured on the grounding electrode conductor (GEC) with a simple CT or ammeter. If you have DC on your GEC and it is connected to the underground gas pipe...
The hazard isn't so much a spark creating fire hazard, but blowing out a pressurized pipeline.
Good luck,
Mark
Hello-
Hope this sheds some light on the situation. Any metallic or conductive material that may become energized inside a building or facility must be bonded together for safety reasons.
Underground metal gas pipes are not permitted for grounding as per 205.52(B)(1) This is where your original safety concerns probably came from.
250.2 and 250.104(B) refer to above ground piping on the customers side of the gas meter.
Underground gas systems are required to have an isolation bushing installed preventing any electrical interconnection between the primary side and the secondary side of the gas meter. In the event of a fault current, this bushing prevents the underground piping from acting as a grounding electrode.
Sometimes there is a small amount of DC present on an AC system. This DC has been responsible for several pipeline explosions by burning pinholes through the metal. (This is the same concept used in electroplating- transferring metal using a direct current) Small amounts of AC current are common on most grounding systems and can be measured on the grounding electrode conductor (GEC) with a simple CT or ammeter. If you have DC on your GEC and it is connected to the underground gas pipe...
The hazard isn't so much a spark creating fire hazard, but blowing out a pressurized pipeline.
Good luck,
Mark
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