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.
Re: to bond or not to bond?#57920 10/24/0511:24 AM10/24/0511:24 AM
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?
Re: to bond or not to bond?#57921 10/24/0502:11 PM10/24/0502:11 PM
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.
Re: to bond or not to bond?#57924 10/24/0509:02 PM10/24/0509:02 PM
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...
Re: to bond or not to bond?#57925 10/24/0511:01 PM10/24/0511:01 PM
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.
Re: to bond or not to bond?#57926 10/24/0511:18 PM10/24/0511:18 PM
... 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
.."if it ain't fixed,don't break it...call a Licensed Electrician"
Re: to bond or not to bond?#57927 10/25/0507:31 PM10/25/0507:31 PM