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Originally Posted by timebuilder

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.

Originally Posted by corny

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.

Originally Posted by Glennhvac

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.

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

Originally Posted by 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.

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

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.

Originally Posted by ironpit

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?

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

Originally Posted by ironpit

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

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

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

The only code provision that I can think of is that the wiring must be protected from damage. I doubt that contact with flex duct is likely to cause damage to NM cable.

Originally Posted by ironpit

I was thinking about shorts or induced voltage that might occur from nearby lightening strikes.I've seen where lightening has induced voltage in wiring and jumped to metal duct.

I think that a magnetic field strength that is sufficient to induce a voltage from a lightning strike would be so close to the building that the induced voltage would be the least of the effects.

Originally Posted by hvacvegas

....what!?!

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.

I was thinking about shorts or induced voltage that might occur from nearby lightening strikes.I've seen where lightening has induced voltage in wiring and jumped to metal duct.

Originally Posted by Glennhvac

I wish we could still even run flex here! What a nightmare those changes caused for attic jobs.

....what!?!

I wish we could still even run flex here! What a nightmare those changes caused for attic jobs.

Originally Posted by ironpit

A conversation with my son-in-law. He is a union electrician and a very good one at that. I didn't think to ask him at the time, but thought about "clearance to metallic objects" later. By the way, I like most of your postsYou seem very good.

Well thank you sir!

I would have thought that clearance to metal is related more toward metal framing, or things that could cut and tear the exterior PVC sheathing on the romex. Which is why I use MC on all commercial jobs.

What your son in law WILL run into, if he hasn't already, is physical touching of romex wire (or any other plastic), to Blazemaster (orange sprinker piping).
They (Code council, or whoever writes this junk) have decided that the plastic in blazemaster will deteriorate if it comes in contact will any type of other plastic related material.
We ran black plastic flex in that particular set of appartments, and we had to get a letter from the manufacturer of the flex, showing that they had done testing related to blazemaster, and that it was allowed to "touch".

A large project (the banks project here in cinci) actually saw deteriation of blazemaster, at the point of contact.

A conversation with my son-in-law. He is a union electrician and a very good one at that. I didn't think to ask him at the time, but thought about "clearance to metallic objects" later. By the way, I like most of your postsYou seem very good.

Originally Posted by ironpit

i haven't been tagged on it yet, but I aways take pain to keep it two inches or more away. Electricians who come behind always run there wire against it.

Whats going on, that made you think about this?

i haven't been tagged on it yet, but I aways take pain to keep it two inches or more away. Electricians who come behind always run there wire against it.