Bonding gas pipe at hot water tank

jaysgardenNovember 25, 2010

My hot water tank's cold and hot water lines are jumped/bonded with a #8 conductor above the dielectric unions. The water lines are copper pipe and the water tank is a power vented model.

Wanted to get some thoughts on if it is necessary to bond the gas piping(1/2" black pipe) at the hot water tank to the hot or cold water lines?


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Nope, quit worrying and eat some turkey hah (:

    Bookmark   November 25, 2010 at 1:44PM
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NEC says all pipes (including gas pipes) capable of being energized are required to be bonded.

How that bonding needs to be accomplished depends upon the type of pipe and your local electric and fuel gas code.

You need to contact your local code office to determine how your gas pipes are permitted and required to be bonded.

Turkey dinner or no Turkey dinner.

Find out from the local AHJ.

Not here.

    Bookmark   November 25, 2010 at 10:22PM
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Ron Natalie

(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.
Informational Note No. 1: Bonding all piping and metal air ducts within the premises will provide additional safety.
Informational Note No. 2: Additional information for gas piping systems can be found in Section 7.13 of NFPA 54-2009, National Fuel Gas Code.

    Bookmark   November 26, 2010 at 8:11AM
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I understand that the gas line cannot be used as the grounding electrode.

Since this hot water tank is a power vented model meaning it uses an electric blower to assist in the venting of the combustion gases, the equipment grounding conductor for the circuit providing power to the blower can be used as the bonding means. Wonder if there is continuity between the two now? I will check.

I did find this answer also:

Is Gas Pipe Grounding Legal?

You must not use an underground metal gas piping system as a grounding electrode. So, what's the confusion all about?

The controversy behind bonding and grounding metal gas piping systems arose when many electrical professionals questioned the rules and regulations of the National Fuel Gas Code (NFPA) 54. For example, Sec. 3.14(a) in NFPA 54 requires each aboveground portion of a gas piping system upstream from the equipment shutoff valve to be electrically continuous and bonded to any grounding electrode. Sec. 250-104(b) of the National Electrical Code (NEC) agrees with this mandate. On the other hand, NFPA 54 [Sec. 3.14(b)] parallels Sec. 250-52(a) of the NEC, which states: "You must not use an underground metal gas piping system as a grounding electrode" No wonder so many people are uncertain.

Let's take a closer look at the rules to help clarify the position of both Codes.

Metal gas piping: NEC Sec. 250-104(b) and NFPA 54 [Sec. 3.14(a)]. Sec. 250-104(b) of the NEC and NFPA 54, Sec. 3.14(a) requires you to bond the aboveground portion of a metal gas piping system to a grounding electrode system for safety reasons. NFPA 54, Sec. 3.15 does not allow you to use aboveground portions of a metal gas piping system or its components as a conductor in electrical circuits. However, NFPA 54, Sec. 3.15, Ex. recognizes under certain conditions, which applies when you are using low-voltage (50V or less) control circuits, ignition circuits, and electronic flame detection device circuits as piping or components of an electric circuit.

You should size the bonding jumper connecting and bonding the metal gas piping to the grounding electrode system as noted in Table 250-66 of the NEC; based on the largest ungrounded service phase conductor. You should size the conductor just as you would size it if it were a metal water pipe isolated from earth ground because of a nonmetallic underground water supply system.

However, some disagree. They believe you should size it from Table 250-122, determined by the size of the overcurrent protection device ahead of the circuit. The only problem we have with this concept and method of sizing is which protective device should you use: the service device, feeder device, or branch-circuit device? Due to this uncertainty, we feel the need for a proposal for the 2002 NEC to clarify which Table to use when sizing this conductor. Depending on where you're working, you should check with the AHJ for their official interpretation.

    Bookmark   November 26, 2010 at 8:40AM
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The branch circuit feeding the power to the heater supplies the ground for the gas line.

Nothing more is required.

Bonding of gas lines is a real problem.

While prohibited as part of the grounding electrode system, it is really hard to convince the current to NOT flow through ALL the conductors connected to any part of teh system grounds,

Depending on local soil conditions, even grounding a steel pipe and a copper line can set up electrochemical corrosion by creating a battery between the dissimilar metals.
Without the ground connection no current would flow, but the bonding and grounding supplies a nice low impedance path.

    Bookmark   November 26, 2010 at 9:19AM
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I checked the continuity between the gas pipe and the ground prong on the plug that supplies power to the power vent fan. Sure enough there is continuity so the EGC in the branch circuit is supplying ground.

    Bookmark   December 3, 2010 at 8:33AM
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