Originally Posted by
Jeff Remas
Gas piping bonding has been greatly debated due to the fact it states "likely to become energized".
This is what the 2008 NEC says (and no changes from 2005): (underlining is mine)
- (B) Other Metal Piping. Where 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 where of sufficient size, or the one or more grounding electrodes used. The bonding 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.
- - FPN: Bonding all piping and metal air ducts within the premises will provide additional safety.
I do not agree with that and my interpretation is that any part of the system can possible come into contact therefore I want to see bonding IAW the service entrance conductors.
If any voltage is supplied to the structure or building, then 'it is possible' that such voltage, by way of its circuit, 'could energize' the "other metal piping system", including "gas piping".
Now, does "it is possible" equate to "is likely to"?
The only answer I can give is this example, which is hard for the other side to dispute and argue against:
"It is possible" for lightning to strike a building. However, "is it likely" that lightning will strike a building? No, if it were "likely" then many more buildings would be struck than actually are struck.
With that being said, the electrical systems in those buildings are "required" to be protected against that "possible" occurrence as though it "were likely" to happen.
Thus, with the same safety standard in mind, is it not "possible" for the gas piping to become energized by the voltage of the service to the building, and, thus, under the same conditions and reasoning as with lightning, is it not "likely" that the protective bonding could be carry the current produced by that voltage energizing the piping, and should not the bonding conductor be sized for that occurrence?
If the answer is "No.", then explain why that same answer to the same question is "Yes." when it comes to the "possibility" of a lightning strike.
Both are just as "possible", those both are, using the same definition, just as "likely".
Thus, use the service size as the circuit rating for sizing the bonding conductor.
Also notice where the bonding jumper is required to go to in the above code reference - I have also underlined that part.