Rigid transitioned to LFMC back to Rigid

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jazer

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Gibsonia, Pa
I have a situation where rigid steel is used in straight runs after penetrating a roof, then transitions to LFMC to compensate for bends, then transitions back to rigid for more straight runs, then, finally, transitions back again to LFMC to hit the disconnect for the equipment on the roof. An equipment ground conductor is run with the circuit conductors. My problem with this is that there is more than 6' of LFMC in this run. I understand that the equipment and enclosures and such are bonded correctly with the seperate EGC, but the rigid raceway seems like it would lose its bonding continuity with more than 6' of LFMC? The raceway is 1 1/4". I am referencing 350.60, then 250.118(6). The circuit meets the requirements of 250.18(6). I guess my ultimate concern is losing the electrical continuity (bonding) of the raceway. Any help?
 
You just said that you ran a Equipment Ground Conductor with your circuit conductors.

The 6 ft rule applys to LFMC when using the LFMC as the ground between say a disconnect &

a piece of equipment.

I think your concern is you have more than 6 ft of LFMC in the middle of the run. Proably not

a problem. If this keeps you up at night, you could run a bond wire from rigid conduit, bond

to LFMC, continue to other end & repeat.
 
You need to make sure you're not exceeding the circuit ampacity indicated on the side of the flex(60 amps?). If you're over it you need to add a bond around the first sealtite to the isolated section of rigid in your run.
 
jazer said:
I have a situation where rigid steel is used in straight runs after penetrating a roof, then transitions to LFMC to compensate for bends, then transitions back to rigid for more straight runs, then, finally, transitions back again to LFMC to hit the disconnect for the equipment on the roof. An equipment ground conductor is run with the circuit conductors. My problem with this is that there is more than 6' of LFMC in this run. I understand that the equipment and enclosures and such are bonded correctly with the seperate EGC, but the rigid raceway seems like it would lose its bonding continuity with more than 6' of LFMC? The raceway is 1 1/4". I am referencing 350.60, then 250.118(6). The circuit meets the requirements of 250.18(6). I guess my ultimate concern is losing the electrical continuity (bonding) of the raceway. Any help?
Click to expand...

Since you have added the seperate EGC with the conductors the length of the FMC is ilrelivent since you are not relying on it for the grounding.
 
John120/240 said:
I think your concern is you have more than 6 ft of LFMC in the middle of the run. Proably not

a problem. If this keeps you up at night, you could run a bond wire from rigid conduit, bond

to LFMC, continue to other end & repeat.
Click to expand...

This is what I am concerned about. Yes it is a metal spiral in the middle and the OCPD is less than 60 amps. I lose sleep over a ground fault in the conduit and the LFMC not being able to carry the fault current.

And just for clarification, I did not install this. I would have spent the extra coin to bend and thread the rigid 90's and such. It seems like it was done in a hurry and/or due to lack of equipment or skill. That is why it worries me......
 
jazer said:
I have a situation where rigid steel is used in straight runs after penetrating a roof, then transitions to LFMC to compensate for bends, then transitions back to rigid for more straight runs, then, finally, transitions back again to LFMC to hit the disconnect for the equipment on the roof.
Click to expand...
You do have a problem with the section of RMC between the two pieces of LFMC.

The starting run of RMC is ok because it has a connection to the EGC through locknuts, connector, or a bond bushing so you're good to the first section of LFMC.

Now, we know the LFMC does not qualify as an EGC per 250.118, which wouldn't be an issue if the next section of RMC connected to equipment in the same manner as the first section but, this is not the case and you now have a section of RMC isolated from an EGC through the two pieces of LFMC.

Roger
 
jazer said:
This is what I am concerned about. Yes it is a metal spiral in the middle and the OCPD is less than 60 amps. I lose sleep over a ground fault in the conduit and the LFMC not being able to carry the fault current.

And just for clarification, I did not install this. I would have spent the extra coin to bend and thread the rigid 90's and such. It seems like it was done in a hurry and/or due to lack of equipment or skill. That is why it worries me......
Click to expand...

The grounding conductor is run from point A to B the entire length and is sized properly correct? If so the LFMC is not serving as the primary grounding path.
 
roger said:
You do have a problem with the section of RMC between the two pieces of LFMC.

The starting run of RMC is ok because it has a connection to the EGC through locknuts, connector, or a bond bushing so you're good to the first section of LFMC.

Now, we know the LFMC does not qualify as an EGC per 250.118, which wouldn't be an issue if the next section of RMC connected to equipment in the same manner as the first section but, this is not the case and you now have a section of RMC isolated from an EGC through the two pieces of LFMC.

Roger
Click to expand...

Thank you, perfectly stated!!
 
Gregg Harris said:
The grounding conductor is run from point A to B the entire length and is sized properly correct? If so the LFMC is not serving as the primary grounding path.
Click to expand...
That doesn't solve the problem of the un-bonded section of RMC.

Roger
 
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