Gas piping grounding?

[cppoly]

250.4(A)(4) says metal gas piping likely to become energized must be bonded via an equipment grounding conductor. 250.52(A)(8)(B)(1) says underground metal gas piping is not permitted as a grounding electrode. How come it's ok to allow current to flow inside a building on a metal gas pipe? Wouldn't this create an explosion in a ground fault condition?

 

[Dennis Alwon]

I tghink the difference is that inside we are using the ground to divert the flow of power from the gas pipe to the service ground. An underground gas pipe is an electrode if the gec were connected to it and we would be diverting lightning strikes and surges to the gas line. Not a good idea. There is usually a dielectric fitting between the underground pipe- usually at the meter- and the inside gas pipe.

 

[cppoly]

Good points, thanks. Lightning sounds like it would be really bad condition too.

 

[mistermudd]

You are actually bonding the gas pipe so that if it was to become energized, it would have a low impedance path to trip the OCPD.

 

[goldstar]

250.4(A)(4) says metal gas piping likely to become energized must be bonded via an equipment grounding conductor.

This is what has to be "clearly defined or determined". As far as I know the only time we're bonding gas lines now is if there is CSST present.

 

[iwire]

The NEC requires all gas lines to be bonded, this is usally accomplished by the EGC of the equipment likely to energize it. Such as the boiler or furnace.


CSST is another issue where the manafacturers are requireing specific bonding requirements that exceed the NEC.

 

[mlnk]

i have heard of AHJs that prohibit bonding to a gas pipe, but cannot remember which city.

 

[renosteinke]

Where does the NEC require all gas lines to be bonded?

The last place I lived had gas only for heat - and the heat was a wall furnace with a standing pilot light. There was NO electrical connection to the gas system anywhere. No fan, no igniter. Gas valve was powered by the thermopile in the pilot flame, and the thermostat worked from a bi-metallic coil.

There's been a lot of confusion over the years regarding 'grounding.' Indeed, the NEC is still confused on this point. Other codes are similarly confused. A better question to ask is "Should I bond the gas line to accomplish "X"? Code will then answer, based on what "X" is.

May I bond to the gas line so it will act as a grounding electrode? No, you may not. NEC says so.

May I bond to the gas line to provide a fault path for a failed gas appliance? NEC says you must.

May I bond the gas line to my grounding electrode, to provide lightning protection? You may - and the plumbing code, fuel gas code, and CSST instructions all say you must when there is CSST present anywhere in the system. (Plese note that "CSST" does NOT include the short flexible whip used to connect appliances).

I know, it's kind of confusing .... whether you are bonding the gas line TO the GEC or whether you are using the gas line AS your grounding electrode depends entirely on which direction you think the electricity will flow. It becomes a word game.

 

[don_resqcapt19]

The NEC requires all gas lines to be bonded, this is usally accomplished by the EGC of the equipment likely to energize it. Such as the boiler or furnace.
...

When the code used the words "may become energized" in place of the current wording of "likely to become energized" I would have agreed that the NEC required bonding for all gas lines. With the wording that is in the code now, I don't agree.

Note that CMP 5 is on record as saying that both set of words have the identical meaning and their intent is, as you stated, to require bonding for all gas lines. I just don't see the words as matching the intent.

 

[Gregg Harris]

Where does the NEC require all gas lines to be bonded?

The last place I lived had gas only for heat - and the heat was a wall furnace with a standing pilot light. There was NO electrical connection to the gas system anywhere. No fan, no igniter. Gas valve was powered by the thermopile in the pilot flame, and the thermostat worked from a bi-metallic coil.

There's been a lot of confusion over the years regarding 'grounding.' Indeed, the NEC is still confused on this point. Other codes are similarly confused. A better question to ask is "Should I bond the gas line to accomplish "X"? Code will then answer, based on what "X" is.

May I bond to the gas line so it will act as a grounding electrode? No, you may not. NEC says so.

May I bond to the gas line to provide a fault path for a failed gas appliance? NEC says you must.

May I bond the gas line to my grounding electrode, to provide lightning protection? You may - and the plumbing code, fuel gas code, and CSST instructions all say you must when there is CSST present anywhere in the system. (Plese note that "CSST" does NOT include the short flexible whip used to connect appliances).

I know, it's kind of confusing .... whether you are bonding the gas line TO the GEC or whether you are using the gas line AS your grounding electrode depends entirely on which direction you think the electricity will flow. It becomes a word game.

The gas service is isolated preventing it from being a grounding electrode. The gas line is bonded after the meter or on propane after the second pressure regulator.

If you have a gas appliance such as a fireplace or HWH that is not electrically conected it would require to be bonded.

 

[don_resqcapt19]

...If you have a gas appliance such as a fireplace or HWH that is not electrically conected it would require to be bonded.

What would requrie that bonding?

 

[iwire]

Where does the NEC require all gas lines to be bonded?

OK, you are correct, I should have said most as most gas lines do in fact connect to electric equipment which IMO means they fall under the likely to become energized mantra.

250.104 Bonding of Piping Systems and Exposed Structural
Steel.

(B) Other Metal Piping. If installed in, or attached to, a
building or structure, a metal piping system(s), including
gas piping, that is likely to become energized shall be
bonded to the service equipment enclosure; the grounded
conductor at the service; the grounding electrode conductor,
if of sufficient size; or to one or more grounding electrodes
used. The bonding conductor(s) or jumper(s) shall be
sized in accordance with 250.122, using the rating of the
circuit that is likely to energize the piping system(s). The
equipment grounding conductor for the circuit that is likely
to energize the piping shall be permitted to serve as the
bonding means. The points of attachment of the bonding
jumper(s) shall be accessible.

 

[iwire]

When the code used the words "may become energized" in place of the current wording of "likely to become energized" I would have agreed that the NEC required bonding for all gas lines. With the wording that is in the code now, I don't agree.

Note that CMP 5 is on record as saying that both set of words have the identical meaning and their intent is, as you stated, to require bonding for all gas lines. I just don't see the words as matching the intent.

I understand your views but I don't think many inspectors do.