Flex gas pipe

[WirenutNH]

Just a FYI,

If you are asked to install a gas fired unit heater and plumber uses (Ward flex or others) flexable gas pipe, there is a requirement by the manf requiring that the solid black iron pipe at service be bonded with a #6 to protect against ligthening strike issues . At this time the only ref in 2008 code is 250-104b that states the equimnet ground conductor can act as this but most units only will have a #12 equipment ground.

 

[Dennis Alwon]

Just a FYI,

If you are asked to install a gas fired unit heater and plumber uses (Ward flex or others) flexable gas pipe, there is a requirement by the manf requiring that the solid black iron pipe at service be bonded with a #6 to protect against ligthening strike issues . At this time the only ref in 2008 code is 250-104b that states the equimnet ground conductor can act as this but most units only will have a #12 equipment ground.

This has been true for quite some time. Apparently the CSST (corrugated stainless steel tubing) had a bad habit of splitting and starting fires if lightning strikes where nearby. The bonding is a manufacturers instruction and must be done to prevent these potential accidents.

 

[mcclary's electrical]

Most CSST man. demand a #6 bond, but be careful, I'm 99% sure that ward flex demands a bond the same size as your GEC. I faild an inspection for using #6 and the man. stated it had to match GEC, which on this particular service was a #4

 

[ivsenroute]

It is a manufacturer's specific bond and 4 of the 5 companies that I researched require a #6 copper bond. None of those that I checked with ever wanted anything larger.

I look at this as a mechanical code issue and not an electrical installation issue. It is the mechanical contractor that installs this product, not the electrician.

Do you as an EC check with the mechanical contractor to see if he is installing CSST so you can put it in your bid?

Who is responsible in your eyes?

 

[mcclary's electrical]

It is a manufacturer's specific bond and 4 of the 5 companies that I researched require a #6 copper bond. None of those that I checked with ever wanted anything larger.

I look at this as a mechanical code issue and not an electrical installation issue. It is the mechanical contractor that installs this product, not the electrician.

Do you as an EC check with the mechanical contractor to see if he is installing CSST so you can put it in your bid?

Who is responsible in your eyes?

Yes, I always find out if there will be any on the job, and yes I think it's the electrician's job. I don't want anybody in my panel, bonding anything that's on my permit. I always do it.

 

[jwjrw]

Our electrical inspector asks and looks at it. We have to get a rough inspection on csst bonding wire if its covered up.Kinda hard to forget to include it here.

 

[don_resqcapt19]

Given that the problems with this stuff have come from nearby lightning strikes, I fail to understand how providing an more effective ground will make the problem go away. It seems to me that it would have the opposite effect...that is a better grounding path will permit it to carry more current and increase the chance of the current punching holes in tubing. (note that this assumes that the problems occurred in installations that were compliant with 250.104(B))

 

[electricmanscott]

Do you as an EC check with the mechanical contractor to see if he is installing CSST so you can put it in your bid?

Who is responsible in your eyes?

Of course I would check. This should now be one of the (many) things that you check on before you bid. This is not new anymore.

 

[mcclary's electrical]

Given that the problems with this stuff have come from nearby lightning strikes, I fail to understand how providing an more effective ground will make the problem go away. It seems to me that it would have the opposite effect...that is a better grounding path will permit it to carry more current and increase the chance of the current punching holes in tubing. (note that this assumes that the problems occurred in installations that were compliant with 250.104(B))

I believe what they are trying to prevent (IMO) with the bigger bond is differences in potential. During a lightning strike, one system (the service) could become induced with a voltage surge. If the other system (the gas piping) piping is only joined by a bond sized per 250.122,,,,the chances of a longer, and stronger difference in potential can occur. BUT, if it is sized per 250.66,,,, The bigger wire helps to equalize both systems quicker, bringing them to the same potential faster, thus preventing (in theory) the CSST from arcing to nearby metal, burning a hole in it, and the rest is history. But I'm only taking a stab at it

 

[don_resqcapt19]

I believe what they are trying to prevent (IMO) with the bigger bond is differences in potential. During a lightning strike, one system (the service) could become induced with a voltage surge. If the other system (the gas piping) piping is only joined by a bond sized per 250.122,,,,the chances of a longer, and stronger difference in potential can occur. BUT, if it is sized per 250.66,,,, The bigger wire helps to equalize both systems quicker, bringing them to the same potential faster, thus preventing (in theory) the CSST from arcing to nearby metal, burning a hole in it, and the rest is history. But I'm only taking a stab at it

The piping bond based on 250.122 will be more than sufficient to raise the potential of the CSST to that of the other bonded items in the building. The size of the bond does not really effect the time it takes to equalize the voltages...it only increases the amount of current that can flow. The CSST should not be flowing current and there should not be a difference in potential between it and other bonded items. If it is carrying current, I don't see how giving it the ability to carry even more current makes it safer.
I doubt that this solution to the problem has any real technical merit.

 

[mcclary's electrical]

The piping bond based on 250.122 will be more than sufficient to raise the potential of the CSST to that of the other bonded items in the building. The size of the bond does not really effect the time it takes to equalize the voltages...it only increases the amount of current that can flow. The CSST should not be flowing current and there should not be a difference in potential between it and other bonded items. If it is carrying current, I don't see how giving it the ability to carry even more current makes it safer.
I doubt that this solution to the problem has any real technical merit.

I agree that it has no merit, I'm simply trying to understand their thinking. I agree that the bigger bond is useless, and they are simply grasping at straws trying to point blame elsewhere for an inferior product.

 

[LarryFine]

Maybe they're seeing it like this:

If the appliance at the end of the CSST is grounded by the supplying circuit's EGC, and the gas main isn't bonded, then either system (the EGC or the gas piping) can become energized and develope a voltage difference to the other, causing current in the CSST.

It sounds like an electrical fire I investigated where the water heater's EGC burned, because it was the only bond between the panel and the water piping. It may have been heavy enough for the 30a circuit, but not for the 200a service, energized in a bad storm.

 

[don_resqcapt19]

Maybe they're seeing it like this:

If the appliance at the end of the CSST is grounded by the supplying circuit's EGC, and the gas main isn't bonded, then either system (the EGC or the gas piping) can become energized and develope a voltage difference to the other, causing current in the CSST.

It sounds like an electrical fire I investigated where the water heater's EGC burned, because it was the only bond between the panel and the water piping. It may have been heavy enough for the 30a circuit, but not for the 200a service, energized in a bad storm.

The CSST is metallic and if it is bonded the interior gas piping is bonded. (bonding of interior gas piping is required by the NEC) The exterior gas supply, if metallic, is isolated from the interior piping by the use of a dielectric union at the line side of the gas meter.
I don't see an increase in the size of the bonding jumper between the electrical grounding system and the CSST as providing any increase in safety or protection of the CSST over that provided by compliance with the current rules in 250.104.
As I recall some of the early court cases over CSST and fire damage resulted in the CSST supplier being required to provide a lighting protection system for the building. I don't see how the increase in the size of the bonding conductor will provide equivalent protection.
I think the safest installation for this stuff would be complete electrical isolation. Even with the bonding a fault to the CSST from a non GFCI or AFCI protected circuit will most likely result in a hole in the tubing and a fire.
In my opinion the use of CSST is the equivalent of wiring your house with drop cord.

 

[cadpoint]

This is a transition point, from hard pipe to foiled metal, let's got with the chareristics of that exists, first... this is a foiled coil to a fitting!

Maybe I'm totally wrong, the Bonding of other services is to null them to the potential of some differential of potential.

We are in the only job where no potential is desired!