LFMC BONDING

[AL ALIPERTI]

LFMC 1 1/2" and larger is interlocked design without an integral bonding wire. When connecting a 480V motor equipment (motor), equipment grounding is achieved through the use of an insulated EGC wire inside the conduit along with the phase conductors. The LFMC is terminated with fittings listed for grounding. NEC 250-100 requires bonding of the raceway itself through means specified in 250.92 (B). However, it the LFMC is not considered continuous how can it be bonded? What happens if there is a wire fault in the 3" LFMC?

 

[Dennis Alwon]

Wouldn't there be a need for a bonding bushing or something of that sort and then wouldn't that insure a good ground?

 

[LarryFine]

There's a difference between bonding the flex and using it as an EGC for the load.

 

[AL ALIPERTI]

There's a difference between bonding the flex and using it as an EGC for the load.

Agreed. Not using the flex as and EGC. Concern is bonding of the flex. How can it be done? Not flex has a PVC jacket so an external bonding jumper would not work. Can the interlocked flex be considered electrically continuous even if the NEC does not recognize it as an EGC?

 

[infinity]

Agreed. Not using the flex as and EGC. Concern is bonding of the flex.

There is no concern. The equipment is bonded via the EGC, the LFMC is bonded via the listed connector. No different than FMC.

 

[AL ALIPERTI]

I was leaning toward this answer. So the interlocked LFMC is considered electrically continuous and satisfies NEC 250-100 for Hazardous Locations?

 

[AL ALIPERTI]

If the interlocked LFMC flex is not considered electrically continuous, bonding one end to the EGC at the termination does nothing to bond rest of the LFMC. An external jumper may satisfy code but it there is a fault inside the flex isn't arcing likely since the LFMC is discontinuous and may not be bonded?

 

[LarryFine]

If the interlocked LFMC flex is not considered electrically continuous, bonding one end to the EGC at the termination does nothing to bond rest of the LFMC. An external jumper may satisfy code but it there is a fault inside the flex isn't arcing likely since the LFMC is discontinuous and may not be bonded?

If it's metallic, it is electrically continuous, even if it does not qualify by itself as an EGC.

If it's genuinely not electrically continuous, then there is nothing to require bonding.

The point is that, if it's conductive enough to require bonding, it's capable of bonding itself.

 

[infinity]

If it's metallic, it is electrically continuous, even if it does not qualify by itself as an EGC.

That's it. The connectors are listed to bond the raceway even when it cannot be used as an EGC.