I will be glad too. It seems it had something to do with lightening charging a gas line then duct work.
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.
Ralph morrison touches on the topic in his book Grounding and shielding/circuits and interference.
"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.