foil flex and electrical code

[timebuilder]

I've seen an example of it. Just don't remember where.

When you remember, send as much info as you can to NFPA.

[ironpit]

I will be glad too. It seems it had something to do with lightening charging a gas line then duct work.

[timebuilder]

I will be glad too. It seems it had something to do with lightening charging a gas line then duct work.

Was the ductwork bonded to the system grounding electrode?

[ironpit]

I don't remember, but it seems like we were talking about bonding and grounding csst. I'm trying to remember. I'll call my son-in-law tomorrow to see if he remembers. It may have been a csst booklet I read.

[timebuilder]

I don't remember, but it seems like we were talking about bonding and grounding csst. I'm trying to remember. I'll call my son-in-law tomorrow to see if he remembers. It may have been a csst booklet I read.

There WAS an issue with CSST and the need for bonding due to a perforation in the steel caused by a lightning strike.

[ironpit]

Ralph morrison touches on the topic in his book Grounding and shielding/circuits and interference.

[corny]

We are allowed to run about 5 feet of flex. Anything else has to be HARD pipe and hand insulated. I think to prevent fumes when the house is burning to the ground.

Man... I remember the pre flex days..... I bet people today would just die if they had to run hard pipe off the trunk to the registers in an attic today.

Or a bad crawl space.

[Glennhvac]

Man... I remember the pre flex days..... I bet people today would just die if they had to run hard pipe off the trunk to the registers in an attic today.

Or a bad crawl space.

Old days? That is what is required again now in all the areas I work in. Insulated hard duct. I had one job where they wanted a second system installed in the attic for a/c only. I figured the hard pipe and insulating it all by hand added probably 20 hours to the job or more plus the material extra cost.

[ironpit]

When you remember, send as much info as you can to NFPA.

couldn't find the info I was looking for, but did find some material in Tru-flex metal hose corp. installation training guide, that states, and I quote

"Even a nearby lightening strike that does not strike a structure directly can cause metallic systems (such as wiring, piping and ductwork) in the structure to become energized.If those systems are not properly bonded, the difference in potential between the systems may cause the charge to arc from one system to another and cause damage to to csst. End Quote.

Which makes me wonder about the bonding and grounding of the complete system , especially if vibration dampening legs are used on the furnace.Not all furnaces I have seen installed have ground wire.
Also if csst requires # 6 ground, I'm rethinking how a metal duct system should be bonded or grounded, or if it should be.