Bonding of Gas Appliance Vents

[aaronm]

Am I correct in my reading of the following to mean that all gas appliance vents must have bonding jumpers installed?

NEC 90.5 Mandatory Rules, Permissive Rules, and Explanatory Material

(A) Mandatory Rules. Mandatory rules of this Code are those that identify actions that are specifically required or prohibited and are characterized by the use of the terms shall or shall not.


NEC 205.104 Bonding of Piping Systems and Exposed Structural Steel

(B) Other Metal Piping. Where installed in or attached to a building or structure, metal piping system(s), including gas piping, that may 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 to one or more of the grounding electrodes used. The bonding jumper(s) shall be sized in accordance with 250.122 using the rating of the circuit that may energize the piping system(s). The equipment grounding conductor for the circuit that may energize the piping shall be permitted to serve as a bonding means. The points of attachment of the bonding jumper(s) shall be accessible.

FPN: Bonding of all piping and metal air ducts within the premises will provide additional safety.

[Jerry Peck - Codeman]

Hi Aaron,

A Type B Gas Vent is not a "other metal piping system", however, there is a recent precedent which indicates the NEC may go that way at some point in the future.

From the 2008 NEC. (underlining and bold are mine)
- 250.104 Bonding of Piping Systems and Exposed Structural Steel.
- - (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.

The original intent of bonding metal piping systems was to protect people from unintentional current and voltage such as from the metal piping system becoming energized or being used as a ground fault path. The intent was not as a protection for lightning strikes as the reason for bonding the vent would be.

As the FPN says, sure, it would be a good idea to bond ALL (metal) piping and metal air ducts, and even vents (which are not air ducts). Note that the FPN left out "metal" when saying "all piping" - there is no good reason to bond CPVC or PEX piping, so the implication is "all (metal) piping".

Once the problems with CSST gas piping being riddled with holes by lightning strikes came to light and bonding of CSST was specifically addressed, it was additionally addressed for lightning strike reasons and not just people protection reasons as other metal piping systems were addressed (besides, CSST was a *metal* gas piping system was was supposed to be bonded to ground *anyway*).

Thus it is reasonable to presume that other "lightning strike" susceptible metal objects, such as Type B Gas Vents sticking up through the roof, would be a good thing to include for the same "lightning strike" protection reasons.

Required at this time by the NEC? No.

Would it be a good idea at this time? Sure. Bonding ANYTHING metal to ground is a "good idea" if that "anything" is susceptible to being energized from any cause, including lightning strikes.