Flex gas line bond.

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S'mise

S'mise

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Michigan
I know gas tubing or CSST require a bond, but what about flexible appliance gas connectors or FAC?

Are short flex gas connectors used for appliances like hot water tanks, dryers and ranges considered CSST?

What does Nec and gas codes say on the matter?
 
Those short sections do not fall under the rules for CSST. Nec just states that the gas pipe needs bonding but it can be bonding with the equipment grounding conductor of the circuit that feeds the gas appliance.
 
Dennis Alwon said:
Those short sections do not fall under the rules for CSST. Nec just states that the gas pipe needs bonding but it can be bonding with the equipment grounding conductor of the circuit that feeds the gas appliance.
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Thanks Dennis. It seems a little contradictory since they'r
e almost identical construction to CSST, but I guess they need to draw the line somewhere.

The idea of needing a bonding conductor along the entire length of CSST tubing, only to connect to a unbonded FAC connector seems silly to me.

Would this be considered "electrically continuous"?
 
Once you bond the csst then everything is bonded. If there is no csst then the black iron bonding is sufficient for the appliance flex.
 
S'mise said:
The idea of needing a bonding conductor along the entire length of CSST tubing, only to connect to a unbonded FAC connector seems silly to me.
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That's not how you bond CSST. Consider that the appliance end(s) of the CSST is grounded via the EGC of the circuit(s) supplying it. A lightning strike nearby can energize the incoming gas line, creating voltage across, and thus current through the CSST, damaging it.

By bonding the incoming gas line piping (typically black-iron pipe) anywhere from the customer's side of the meter to wherever it is nearest to the electrical system (like you would bond to water pipe), you eliminate that voltage gradient across the lengths of the CSST.
 
LarryFine said:
That's not how you bond CSST. Consider that the appliance end(s) of the CSST is grounded via the EGC of the circuit(s) supplying it. A lightning strike nearby can energize the incoming gas line,
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My understand is that the bonding jumper goes from one end of the csst to the other like this.Screenshot_2018-09-27-22-50-16-1.jpg

So when lighting strikes the CSST will be fine but the FAC connection will blow up.
 
We have always done it as Larry stated. Can you imagine what you would have to do if there were 8-10 runs if we had to run a wire along the entire length of the csst.
 
Dennis Alwon said:
We have always done it as Larry stated. Can you imagine what you would have to do if there were 8-10 runs if we had to run a wire along the entire length of the csst.
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Yes, there's some misinformation out there. What you two say makes sense, but I don't fully have my mind around this yet.

In my mind, most explosions of CSST are because of lighting strikes which can cause high current to flow through the corrugated tube and blow holes in it. Adding a bond wire along it supplements it to allow more fault current to safety pass and will equalize voltage differentials.

Assuming the gas pipe is already bonded at its source to the grounding system, what good does it do when someone adds a section of CSST to the existing black pipe to require a bond at the end of this already bonded ridged pipe? How does this protect the section of CSST?

Perhaps I'm thinking about this wrong but when lighting strikes the ground, its path could be from the gas pipe source, or from the grounded appliance going the other way.


Wouldn't it be better to jumper around the weakest point?
 
I've read that and understand the requirements, I'm just not sure of its effectiveness.

It would certainly help if the gas pipe wasn't bonded or didn't have continuity, but in many cases its just running expensive #6 copper for nothing.


Another burden on the electrician is having to read through plumbing instructions in order to be code compliant.

Thanks fot your opinion.
 
S'mise said:
My understand is that the bonding jumper goes from one end of the csst to the other like this.View attachment 21270

So when lighting strikes the CSST will be fine but the FAC connection will blow up.
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All that does is create parallel paths. Whichever path is less impedance carries more current. With lightning that lesser impedance path isn't always as obvious as with regular AC voltage/current. On top of that with a fairly direct hit you have a lot of current and a lot of damage regardless, it is those nearby strikes that put transients into a facility that they are mostly concerned with for the added bonding.

I think the intent should be to create low impedance path to ground that makes an attempt to bypass the gas piping, but if there is continuity to ground on the appliance at the other end it is nearly impossible to say there will never be transient current through the piping either, you have only made an effort to divert some of the current with the added bonding.
 
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