concentric ko's on panel

[Cleveland Apprentice]

I am replacing a panel (old Federal Pacific fire hazard) with Siemens box. There are 4 existing conduits going to box from 1/2" to 1" The service is 100 amp fed from 1 1/4" greenfield. I know I need to install a grounding bushing on conduits/greenfield if using a box with concentric ko's on service, but does this include feeders and BC conduits if conduit itself is the egc?

 

[augie47]

Basically FMC is not an equipment ground for circuits greater than 20 amps, so unless you are using a bond busing to connect a jumper around the FMC there is no advantage of using one on any circuit greater than 20 amps including services.

 

[Dennis Alwon]

No bonding bushing is required for the branch circuits or feeders unless the voltage is over 250v

 

[Dennis Alwon]

Basically FMC is not an equipment ground for circuits greater than 20 amps, so unless you are using a bond busing to connect a jumper around the FMC there is no advantage of using one on any circuit greater than 20 amps including services.

Would you still need to bond if there is an egc in the greeenfield? I didn't think so.

 

[Cleveland Apprentice]

can you give me section in article 250? I think inspector may make me use ground bushings and city uses NEC - no local code. Thanks

 

[augie47]

For services, 230.43 would require a equipment bonding jumper around the flex.
On feeders and branch circuits, 250.118 (5) limits FMC to 20 amps as an equipmemt ground.
I see no reason a bonding bushing, as such, to be required on circuits over 20 amps as you would be grounding something that can not be used as a ground.

 

[Cleveland Apprentice]

thanks augie and others for replies

 

[infinity]

One other thing to remember when using FMC as an EGC you're limited to 6' in length.

 

[Cleveland Apprentice]

One other thing to remember when using FMC as an EGC you're limited to 6' in length.

I didn't know that. I've seen houses with FMC with no egc pulled. I always pull an egc. I don't trust FMC for grounding in case connector pops loose. Thanks

 

[hurk27]

No bonding bushing is required for the branch circuits or feeders unless the voltage is over 250v

That is over 250 volts to ground, not between phases, and the requirement is only for concentric ko's as 250.97 exception even eliminates it where no concentric ko's are encountered.

( I know you know this Dennis, but I was just trying to make sure they knew)