Bonding Gas Piping

[augie47]

Question has come up locally in regard to gas piping. In 250.104 the Code states one method of bonding allowed is :, Equipment grounding conductor for the circuit that is likely to energize the piping system.
Most of the appliances installed in this area have a short section of CSST connecting the gas hard pipe to the appliance and the assembly has a rubber washer. Does that short CSST connection still provide an adeqauate ground path for bonding the gas pipe ?

 

[Dennis Alwon]

As I understand it that short pipe is not CSST. It does not require extra bonding and to my knowledge is still fine for grounding.

 

[LarryFine]

Question has come up locally in regard to gas piping. In 250.104 the Code states one method of bonding allowed is :, Equipment grounding conductor for the circuit that is likely to energize the piping system.
Most of the appliances installed in this area have a short section of CSST connecting the gas hard pipe to the appliance and the assembly has a rubber washer. Does that short CSST connection still provide an adeqauate ground path for bonding the gas pipe ?

First, not all flexible gas tubing is CSST (Corrugated Stainless Steel Tubing). Second, 250.104 is referring to the appliance end of CSST sections being bonded, not the supply end.

Gas pipe bonding is to make sure that the supply end (i.e., the incoming supply from outside) is always at the same potential as the appliance end, to avoid current on the CSST.

If lightning strikes near a house, voltage can be impressed on the gas piping coming into the house. The pipe bonding acts as an equipotential bond around the CSST sections.

 

[augie47]

Understand the CSST bonding and, as Dennis points out, the flexible gas connection fittings I am questioning is not the same as CSST gas piping. The question is more along the line of confirming that the short flexible connections
provide an adequate ground path tot the had pipe gas system.

 

[Dennis Alwon]

I have not dealt with those fittings but an ohm meter should tell you what you need to know

 

[Dennis Alwon]

Is this what you are talking about. This one does not have a visible gasket

 

[augie47]

An ohm meter does show continuity so perhaps we should have no concern. I posted in hopes someone might know if there has been any evaluation of the ground path.

 

[infinity]

Even if it had a gasket doesn't have a large amount of metal to metal contact with the threads like in Dennis' photo?

 

[electrofelon]

Gas pipe bonding is to make sure that the supply end (i.e., the incoming supply from outside) is always at the same potential as the appliance end, to avoid current on the CSST.

If lightning strikes near a house, voltage can be impressed on the gas piping coming into the house. The pipe bonding acts as an equipotential bond around the CSST sections.

Larry, kinda going from memory here so maybe I'm off base, but not sure I agree. Seems the wording in the code is (something like) "egc of equipment likely to energize the gas piping shall be suitable for bonding the gas pipe", so it seems they are concerned about the appliance end not the supply end. Following this reasoning, I would say then that if there is a dielectric union that the pipe on the supply side of it isn't likely to become energized so no bonding required.

 

[LarryFine]

Larry, kinda going from memory here so maybe I'm off base, but not sure I agree. Seems the wording in the code is (something like) "egc of equipment likely to energize the gas piping shall be suitable for bonding the gas pipe", so it seems they are concerned about the appliance end not the supply end. Following this reasoning, I would say then that if there is a dielectric union that the pipe on the supply side of it isn't likely to become energized so no bonding required.

Yes, the appliance's EGC is adequate for bonding the piping to the appliance.

I am talking about bonding the incoming piping, so any CSST between the incoming piping and the appliance piping is effectively bypassed, so that both ends of the CSST will always be at the same potential, avoiding any current on it.

The effectiveness of such a bond is actually dependent on the EGC of the appliance effectively bonding the appliance's piping. So, we're not disagreeing. I'm not sure whether non-CSST flexible gas whips are adequate to bond piping.

 

[infinity]

I've never heard of the flex gas connections requiring bonding in fact several brands of CSST do not require additional bonding either.

 

[zbang]

From http://csstsafety.com/CSST-FAQs.html

QUESTION: What does CSST look like?

ANSWER: CSST is often coated with a yellow, or in some cases, a black exterior plastic coating. CSST should NOT be confused with flexible gas appliance connectors - the product that joins a moveable appliance to your home or building's gas supply line.

(underline added)

 

[jusme123]

Is this what you are talking about. This one does not have a visible gasket

....but has pipe thread sealant, which does effect the grounding resistance .

 

[LarryFine]

The three connectors are flare fittings, which normally use no sealant, so the compound must be for the pipe-thread ends.

While pipe sealant fills voids and lubricates, I can't imagine that it would impede metal-to-metal contact and conductivity.

 

[romex jockey]

Yes, the appliance's EGC is adequate for bonding the piping to the appliance.

I am talking about bonding the incoming piping, so any CSST between the incoming piping and the appliance piping is effectively bypassed, so that both ends of the CSST will always be at the same potential, avoiding any current on it.

The effectiveness of such a bond is actually dependent on the EGC of the appliance effectively bonding the appliance's piping. So, we're not disagreeing. I'm not sure whether non-CSST flexible gas whips are adequate to bond piping.

ground faults and lightning are two separate issues that, to my understanding , 250.104 B 1 adresses

(B) Other Metal Piping. If installed in or attached to a build‐
ing or structure, a metal piping system(s), including gas piping,
that is likely to become energized shall be bonded to any of the
following:
(1) Equipment grounding conductor for the circuit that is
likely to energize the piping system

That said, 1,000,000 volts acts differently than 120 volts ......

~RJ~

 

[infinity]

All gas pipe uses some type of sealant on the standard threads (not the flared ends) so that should not be an issue.

 

[jusme123]

All gas pipe uses some type of sealant on the standard threads (not the flared ends) so that should not be an issue.

It is if your relying on that connection for a ground

 

[ActionDave]

It is if your relying on that connection for a ground

But you are not. Gas pipe is neither an equipment ground or a grounding electrode.

 

[LarryFine]

If a section of pipe is not grounded by the EGC of the appliance because of sealant, then that section also can not be energized by that appliance.

 

[Dennis Alwon]

IMO, there is no way the sealant will cause an issue with grounding