Thread: Bonding to HVAC duct

Can copper water pipes be bonded and then bonded to HVAC duct.

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Sounds "unorthodox" -- and stupid -- to me.

FYI. If the water pipe serves as the only source of ground, I'd write it up since today's code prohibits pipes as the only ground source.

You cannot use a water pipe electrode for an additional bond past the fist 5' of where it enters the structure. At a point past 5' a water pipe is no longer considered an electrode.

See
250.104(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.

Originally Posted by Speedy Petey

You cannot use a water pipe electrode for an additional bond past the fist 5' of where it enters the structure. At a point past 5' a water pipe is no longer considered an electrode.

Actually, you can.

You are not allowed to GROUND the water pipe past 5 feet and then consider it a GROUNDing electrode, but the original post asked about BONDing it, and you can bond it.

I believe the intent of bonding the duct work is to equalize electrical potential between it and other conductive materials.

In the case of a lightning strike for instance, if all metal components have equal potential because they're bonded together, the chance of arching which can start fires or perforate CSST is reduced.

Originally Posted by Jerry Peck

Actually, you can.

You are not allowed to GROUND the water pipe past 5 feet and then consider it a GROUNDing electrode, but the original post asked about BONDing it, and you can bond it.

So you think it is OK to bond a water pipe, then down the line, bond from the water pipe to a heating duct? If so then I disagree.
If it were building steel it would be OK, but not a water pipe.

There might be a misunderstanding between grounding and bonding going on here.

Originally Posted by Joe Funderburk

Sounds "unorthodox" -- and stupid -- to me.

FYI. If the water pipe serves as the only source of ground, I'd write it up since today's code prohibits pipes as the only ground source.

Not stupid to me, unorthodox for some locals, maybe. At least one of the cities here (Frisco, where I believe the CSST issue was first brought to light) actually requires all the metal in the attic to be bonded together and down to the GEC. So every metal gas pipe, b-vent, pipe, etc. We use flex duct almost exclusively but if it was metal duct, I'm sure they would require that be bonded also. Of course you have to keep in mind we need a little more robust bonding here due to the lack of basements and sticking everything up in the attic. Two water heater vent pipes, two or three furnace vent pipes sticking up in the air two or three stories above the prairie make pretty decent lightening rods whether intended to be so or not.

Originally Posted by Jim Luttrall

Not stupid to me, unorthodox for some locals, maybe. At least one of the cities here (Frisco, where I believe the CSST issue was first brought to light) actually requires all the metal in the attic to be bonded together and down to the GEC. So every metal gas pipe, b-vent, pipe, etc. We use flex duct almost exclusively but if it was metal duct, I'm sure they would require that be bonded also. Of course you have to keep in mind we need a little more robust bonding here due to the lack of basements and sticking everything up in the attic. Two water heater vent pipes, two or three furnace vent pipes sticking up in the air two or three stories above the prairie make pretty decent lightening rods whether intended to be so or not.

I agree with "not so stupid". We've all been in the older crawlspace where the up grade wiring hangs from water pipes and metal ducts. If the furnace or air-handler has a noise isolation collar then the ducts are not grounded at all. When a wire gets pulled across a sharp corner it can short to the duct and not trip any breaker. When in a crawl like that be sure to at least touch the duct with you hand before squeezing between it and the wet ground. (voltage sniffer is better but do at least the minimum)

Originally Posted by John Dirks Jr

There might be a misunderstanding between grounding and bonding going on here.

There "IS" a misunderstanding between grounding and bonding going on here, and all we can do it address what is stated, which was "bonding", not "grounding".

There is nothing which prohibits the metal duct from being bonded to the bonded interior metal water piping system. Note the key word used here is "bonded".

I for one am well aware of the difference between bonding and grounding.

Originally Posted by Jerry Peck

There is nothing which prohibits the metal duct from being bonded to the bonded interior metal water piping system. Note the key word used here is "bonded".

The way this is written says that any metallic piping systems must be bonded back to the service or a service electrode. Info Note #1 says bonding ducts is a good idea also. I read this as saying bonding ducts should be done in the same fashion.

(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.

I may be wrong, but I don't feel I am.

Originally Posted by Speedy Petey

I for one am well aware of the difference between bonding and grounding.

I was sure of that, but this is what you said and what you said is all I had to go on ...

Originally Posted by mathew stouffer

Can copper water pipes be bonded and then bonded to HVAC duct.

Originally Posted by Speedy Petey

You cannot use a water pipe electrode for an additional bond past the fist 5' of where it enters the structure. At a point past 5' a water pipe is no longer considered an electrode.

No mention was made of grounding or using anything as an electrode, so you had ... still have ... me stumped on how you got from "bonding" to "electrode" (which is "grounding").

Originally Posted by Jerry Peck

I was sure of that, but this is what you said and what you said is all I had to go on ...





No mention was made of grounding or using anything as an electrode, so you had ... still have ... me stumped on how you got from "bonding" to "electrode" (which is "grounding").

Well, I tried to clarify in post #12. If that is not clear enough I am not sure what to write.
Sorry.