Vent Bonding

[A.D. Miller]

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.

[Jon mackay]

No,
A vent system for an appliance is not large enough to warrant bonding to the ground (at least in most cases)
The intent is for large metal objects or systems within a structure that conduct electricity such as gas lines, water lines, duct work, etc.
If they are not bonded to the ground then conceivably a live wire that comes in contact with the large metal object would not trip the breaker and energize the object.
This is the reason for those water meter jumpers and other jumper wires we hear so much about.

[A.D. Miller]

No,
A vent system for an appliance is not large enough to warrant bonding to the ground (at least in most cases)
The intent is for large metal objects or systems within a structure that conduct electricity such as gas lines, water lines, duct work, etc.
If they are not bonded to the ground then conceivably a live wire that comes in contact with the large metal object would not trip the breaker and energize the object.
This is the reason for those water meter jumpers and other jumper wires we hear so much about.

JM: So then, you are saying that 4" and larger Type-B vents which penetrate the roof are not subject to becoming energized, by lighting for example?

[Jon mackay]

Well ya never know, but if lighting hits an appliance vent I would not want that connected to my electrical system.. he he

I believe that the code intent is for objects that travel throughout the home and to protect from wiring within the home. vent systems usually will go either into a chimney or up through a chase to the exterior which make them a lot less susceptible to electrical wiring.

[A.D. Miller]

Well ya never know, but if lighting hits an appliance vent I would not want that connected to my electrical system.. he he

I believe that the code intent is for objects that travel throughout the home and to protect from wiring within the home. vent systems usually will go either into a chimney or up through a chase to the exterior which make them a lot less susceptible to electrical wiring.

JM: All vents here for gas furnaces and water heaters penetrate the roof with no chase. This includes some chimneys.

[Roger Frazee]

I have always understood this section of code to mean metal likely to be energized. So the "shall be" language would apply to ' likely to be energized ' metal piping.

So what exactly is "likely to be energized ". In my opinion for the situation you are asking about the the piping for the vent would fall under "likely to be energized." this is due to the fact that an electrical connection is occurring from the branch circuit supply conductors at the interface with the controls of the furnace.

However I would think that the egc connection (in the wiring compartment) to the furnace frame from the branch circuit for the supply wiring of the appliance would meet the "shall be bonded" requirement since the vent pipe & furnace are common.

I do not think that "likely to be energized" means a lighting branch circuit in close proximity to the vent pipe. However due to what could be a poor electrical fault path from the vent pipe to the furnace metal it certainly would not hurt anything to extend the "likely to be energized" to another circuit that might energize the furnace vent and run a bonding wire sized to the circuit egc that you feel might energize the vent pipe. In my experience I have never seen this done but I have seen metal air ducts bonded so there is a comparison there in my opinion.

[Ted Menelly]

The gas line should already be covered. The flue likely to be energized or not is not suppose to have contact with wood or flammable goods and distance from them maintained. As far as lightening hitting it the electric charge would continue to the water heater or furnace but again their grounding should be taken care of already. Even the dryer where the dryer vent goes out a side wall or roof. The equipment should be grounded already.

[Jim Luttrall]

AD, have you seen the Frisco requirement for bonding all the flue pipes, etc.?
I think Nolan sent a scanned copy of their requirements to me a while back.
I don't know if they passed an amendment or just interpret the code section you posted to arrive at their requirements.
Of course they are pretty proactive and were instrumental in bringing about the whole CSST bonding from what I understand.

I'll look to see if I can locate the Frisco document.

[Jim Luttrall]

Looks like an amendment, not just and interpretation.
Gas Line/Lightning Protection Systems (http://www.ci.frisco.tx.us/departments/fire/firemarshal/Pages/GasLineLightningProtectionSystems.aspx)
See ordinance 03-07-59

[Richard Soundy]

AD,

It has always been my understanding that "NEC 205.104 Bonding of Piping Systems and Exposed Structural Steel" instructions are for "Stray Voltages" and or accidental energizing of metal piping.

Note the exception - "The equipment grounding conductor for the circuit that may energize the piping shall be permitted to serve as a bonding means." I am sure you will find (in most cases) that there is already an equipment ground (green wire) serving this purpose.

Now Surge Voltages or Lightening strikes are very different and should one wish to add this type of protection, then special bonding methods should be used - wire would not hack it and copper straps having max peripheral area would be the choice.

Regards - Richard

[Gunnar Alquist]

AD,

From my understanding and reading of the NEC, the only requirement is for the water supply and gas piping. I believe the FPN at the end of this section covers bonding of flue pipes as a suggestion rather than a requirement.

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


My own imperfect interpretation. I wish the NEC would clarify some of this stuff.

[Jerry Peck]

AD,

From my understanding and reading of the NEC, the only requirement is for the water supply and gas piping. I believe the FPN at the end of this section covers bonding of flue pipes as a suggestion rather than a requirement.

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


My own imperfect interpretation. I wish the NEC would clarify some of this stuff.


Correct.

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.

[Ken Rowe]

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

NEC 205.104 Bonding of Piping Systems and Exposed Structural Steel



Appliance vents are neither piping or structural steel.

[A.D. Miller]

Looks like an amendment, not just and interpretation.
Gas Line/Lightning Protection Systems (http://www.ci.frisco.tx.us/departments/fire/firemarshal/Pages/GasLineLightningProtectionSystems.aspx)
See ordinance 03-07-59

JL: Thanks. I have seen that info. It is an amendment that sprang forth from an interpretation by a CBO that actually understands the English language, and seems genuinely concerned about the safety of his constituents. A rare bird in these parts. Their department is not perfect, but comes as close as it gets in North Texas.

[A.D. Miller]

JP and Others:

Yesterday I did not have time to be specific regarding the situation that gave rise to this thread. I had a little conference with a attorney client, the builder and the chief plumbing and electrical inspectors from the Village of OiVeh (name altered to protect the guilty). The house was built in 2005, used as a builder's model, and went under contract for sale this past December as a new home (this is standard [openly deceptive] practice here - maybe elsewhere).

The house was plumbed with PEX and CSST. The CSST was not bonded at the manifold as required. Additionally, it was installed directly against the roof decking in two locations. There were no sediment traps on the furnaces or water heaters - the list goes on for fifty pages.

The builder contended, as they all do, that the Village of OiVeh gave the house a final green tag, so all was code-compliant. Right. The inspectors contended that:

(1) No sediment traps are required because we do not have "wet gas" in the area. And this even though I had a hard copy of the code to illustrate where drip legs and sediment traps, though similar in appearance, are not interchangeable. Shouldn't a "chief plumbing inspector" and member of the NCTCOG plumbing advisory board already know this?

(2) No bonding of the CSST manifold is required. While it is true that the 2004 Gastite manual would be applicable for a house built in 2005, the house was being sold as "new". We now know that Gastite came out with a bulletin in 2007 (http://ci.owatonna.mn.us/wp-content/uploads/2009/06/gastite_tb2007.pdf) requiring bonding of the manifold. Last time I looked this was 2010.

(3) No protection of the CSST in contact with the roof surface is required. The reasoning: the roof is concrete tile, so the likelihood of nail damage in a re-roofing scenario is nil. Huh?

Of course there were a myriad of other typical issues that Texas "builders" either refuse to do or the area municipalities refuse to enforce (oh yeah, those two reasons are actually one in the same, aren't they?). I just think that the insignificant cost of installing a few bonding jumpers and a couple of steel protector plates, and maybe even four sediment traps in order to make a client both safe and happy is not too much to ask. Especially when it is required.

But that's just me.:D

[David Bell]

NFGC came out with bonding requirement in oct 2008. Here in CT it is probably the first thing town inspectors look for.

[A.D. Miller]

NFGC came out with bonding requirement in oct 2008. Here in CT it is probably the first thing town inspectors look for.

DB: Down here they are either forced or paid not to look.:D