NEC 250.52 B metal gas piping systems

[Jpflex]

If underground metal gas piping systems are not permitted to be used as a grounding electrode according to 250.52 B, then why are metal gas piping systems required to be bonded by 250.104 (B)?

After all a gas pipe does not care if you label it as a grounding electrode or not but if you bond it to the grounding electrode system just like all other grounding electrodes, then does it not become an extension to ground and a grounding electrode?

 

[HEYDOG]

In case the gas pipe accidentally became energized. Where a gas pipe is ran to a gas furnace the equipment grounding conductor that is installed with the branch circuit conductors would satisfy this requirement.

 

[hbiss]

Most times the gas utility will install a dielectric fitting between the incoming underground gas line and the gas meter. This assumes an old metallic gas line. All newer installations are plastic. So, a gas service would not suffice as a GEC and isn't required to.

-Hal

 

[jaggedben]

With older gas installations that may not have the dielectric fitting I think it's a great question. You're kind of damned if you do, damned if you don't.

 

[Jpflex]

Most times the gas utility will install a dielectric fitting between the incoming underground gas line and the gas meter. This assumes an old metallic gas line. All newer installations are plastic. So, a gas service would not suffice as a GEC and isn't required to.

-Hal

So you would bond upstream of the gas meter dielectric coupling to separate meter from underground gas pipes? But what is the meter was older and did not have such an isolating coupling but was one solid metal gas metal line? If I bonded premises gas piping system to premises grounding electrode system according to 250.104B without this coupling would I fail inspection?

And why does code 250.53 A 2 require a rod, pipe or plate grounding electrode to be supplemented by an additional electrode such as those in 250.52 A 2 through A 8?

If you follow this logic then supplementing a grounding rod pipe or plate electrode with a supplemental concrete encased electrode which by itself would not require a supplemental electrode invalidates needing a supplemental ground rod?

 

[Jpflex]

With older gas installations that may not have the dielectric fitting I think it's a great question. You're kind of damned if you do, damned if you don't.

Seen this response after

 

[hbiss]

why does code 250.53 A 2 require a rod, pipe or plate grounding electrode to be supplemented by an additional electrode such as those in 250.52 A 2 through A 8?

Read it. "A single rod, pipe, or plate electrode shall be supplemented by an additional electrode..."

Single electrode. This is why we install two ground rods unless the ground resistance with one is verified to be 25 ohms or less. Read the exception.

So you would bond upstream of the gas meter dielectric coupling to separate meter from underground gas pipes? But what is the meter was older and did not have such an isolating coupling but was one solid metal gas metal line? If I bonded premises gas piping system to premises grounding electrode system according to 250.104B without this coupling would I fail inspection?

It's not your job to inspect the gas piping system. It also wouldn't matter if there were no isolation between the interior piping and outside piping. The Code only says that we have to bond the interior gas piping to the equipment grounding conductor for the circuit that is likely to energize the piping system, the grounded conductor at the service or the grounding electrode conductor. (See 250.104(B))

Generally, unless older CSST tubing is in use, the grounding conductor of the gas appliance (the circuit that is likely to energize the piping system) is sufficient to provide the bonding.

-Hal

 

[Jpflex]

Read it. "A single rod, pipe, or plate electrode shall be supplemented by an additional electrode..."

Single electrode. This is why we install two ground rods unless the ground resistance with one is verified to be 25 ohms or less. Read the exception.



It's not your job to inspect the gas piping system. It also wouldn't matter if there were no isolation between the interior piping and outside piping. The Code only says that we have to bond the interior gas piping to the equipment grounding conductor for the circuit that is likely to energize the piping system, the grounded conductor at the service or the grounding electrode conductor. (See 250.104(B))

Generally, unless older CSST tubing is in use, the grounding conductor of the gas appliance (the circuit that is likely to energize the piping system) is sufficient to provide the bonding.

-Hal

So you don’t run a bonding jumper from the outside metal gas piping to the grounding electrode system? (I’m aware this would make it readily a grounding electrode in violation - but nonetheless must be ground bonded)

Otherwise you say bond the interior gas pipe to equipment grounding / bonding jumper from a circuit likely to energize it (in proximity). Not sure how this works or if disturbing drywall would be necessary to do this (which doesn’t seem feasible)?

 

[jaggedben]

Had one major AHJ where all the inspectors insisted on either a bond to the GEC or bonding at the water heater. You couldn't hit the gas along the way with a jumper between two electrodes, but you could c-tap a jumper branching off that same wire. Go figure.

oh, and definitely any bond had to be on the customer side of the gas meter. Not sure if that was in case the utility changed the meter, or so that it wasn't bonding the riser in contact with the earth (if there was a dielectric fitting). But probably both.

 

[ramsy]

Generally, unless older CSST tubing is in use, the grounding conductor of the gas appliance (the circuit that is likely to energize the piping system) is sufficient to provide the bonding.

Never met a licensed electrician familiar with the Gas Code that specifies CSST bonding.

You must be spying on plans, inspectors, or plumbing monkeys?

 

[LarryFine]

The appliance end of CSST is bonded by the EGC of the appliance. A nearby lightning strikes can drive current through the CSST by energizing the solid piping connected to the meter end. Bonding the latter to the service EGC/grounding bus effectively bonds both ends of the CSST together, bypassing that current.

 

[ramsy]

Gas Code governs if bonding around CSST is required, and 20A wire is not adequate. .

CSST listing requirements for arc suppression are tested against ignition of gas within, regardless if current source is from an appliance SSC fault, utility excursion, or lightning.

No EC, EE, or NEC changes the gas code.

 

[Sberry]

One I did the insp was a fill in guy just before he became the head nut. Pretty worried about the 4 to the water system but seemed to think the 15A wire to the gas pipe was adequate. It might be an irrational fear but I like the 10 better.

 

[ActionDave]

One I did the insp was a fill in guy just before he became the head nut. Pretty worried about the 4 to the water system but seemed to think the 15A wire to the gas pipe was adequate. It might be an irrational fear but I like the 10 better.

It's more than an irrational fear, it makes no sense. The only reason we need to bond anything is to clear a fault, and if you don't think a 15 amp wire is capable of clearing a fault on a 15 amp circuit then you need to run ten gauge wire everywhere you have a circuit, that would include 20A circuits because they are only protected by twelve gauge wire, not just the ones that serve gas appliances.

 

[don_resqcapt19]

Gas Code governs if bonding around CSST is required, and 20A wire is not adequate. .

CSST listing requirements for arc suppression are tested against ignition of gas within, regardless if current source is from an appliance SSC fault, utility excursion, or lightning.

No EC, EE, or NEC changes the gas code.

Very true, but that extra bonding is not the responsibility of the electrical contractor...it is the responsibility of the contractor that installed the CSST. That contractor can either install the NFPA 54 required bonding or hire the EC to do it.

 

[rc/retired]

Very true, but that extra bonding is not the responsibility of the electrical contractor...it is the responsibility of the contractor that installed the CSST. That contractor can either install the NFPA 54 required bonding or hire the EC to do it.

Correct! When I inspected a gas line with CSST, and it wasn't bonded, and the test was ok, my report would be, "Gas line test ok, bond CSST per gas code".
I never failed the EC.

One job, the GC, EC and gas installer were arguing over who is responsible for bonding the CSST. I told them my son will do it for $500 cash.
They settled it quickly.

Ron

 

[don_resqcapt19]

The appliance end of CSST is bonded by the EGC of the appliance. A nearby lightning strikes can drive current through the CSST by energizing the solid piping connected to the meter end. Bonding the latter to the service EGC/grounding bus effectively bonds both ends of the CSST together, bypassing that current.

Yet one of the reasons that CMP 5 did not include the CSST bonding in Article 250 was that the proposers of that requirement could not supply any technical justification that the bonding would solve the problem of energy from nearby lighting strikes punching holes in the CSST. Another reason was that that bonding is a form of lighting protection and not within the scope of the NEC.
The original recommendations to prevent lightning related CSST fires did not include the currently accepted bonding. They were:

1) convert the structure to electricity only and remove all gas delivery;
2) retain gas but remove all CSST from the structure and install black iron pipe,
or
3) prevent lightning from contacting the CSST which would prevent perforation and ensuing fire–i.e., install a NFPA 780 type lightning arrestor system (so called Ben Franklin system).

 

[Sberry]

It's more than an irrational fear, it makes no sense. The only reason we need to bond anything is to clear a fault, and if you don't think a 15 amp wire is capable of clearing a fault on a 15 amp circuit then you need to run ten gauge wire everywhere you have a circuit, that would include 20A circuits because they are only protected by twelve gauge wire, not just the ones that serve gas appliances.

Its a big enuf bond for any circuit in the place, not just the one to the appliance. This would include water heaters ranges and dryers. This was not with the circuit conductors but a separate bond to the piping.

 

[ActionDave]

Its a big enuf bond for any circuit in the place, not just the one to the appliance. This would include water heaters ranges and dryers.

Those would be covered by the circuit that serves them.

This was not with the circuit conductors but a separate bond to the piping.

Then it would not be required by the NEC.

 

[Sberry]

I guess I can spoon feed this.

Those would be covered by the circuit that serves them.

While in theory this is true I cant recall seeing a compliant install lately involving a dryer . Some cant even use a cord connector let alone wire them right. Found an electric water heater 2 days ago not grounded, had a green and a white, both taped off but hooked in the panel. Secondly,,, cant see where I said it was a code requirement other than the language that it be grounded for the largest circuit that would potentially energize it. While it is connected by a 15A circuit to the furnace with a 15 wire there are 30 other 20A circuits in the place.
Lets say we have copper water pipe in a house with 20 and 30 circuits but the feed is plastic so it doesnt have a 4 running to it,,, what wire is required to bond it? Would be upsizing this connection be some kind of violation?