Equipment Grounding Conductor

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janderson

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I understand that rigid metallic conduit is acceptable for use as an Equipment Grounding Conductor. If RMC is used instead of a conductor is there a bonding bushing required at each end? If so what size conductor is required on the bushing?
 
You would only be required to use a bonding busing in a few very specific instances, and if you did install bonding bushings on a feeder or branch circuit raceway the jumper would be sized per 250.122 just like a wire EGC.
 
Thanks Bob. So, just to make sure I understand, this is an 800 amp feeder to a large equipment control panel. Two parallel runs of what should be 600 MCM - I don't need to pull in a 1/0 EGC?
 
A grounded bushing would need to be used if there are concentrics where the conduit terminates. The ground wire from the bushing to the ground lug would be sized according the feeder size, just as if you were to run an EGC (equipment grounding conductor).
If there are no concentrics, you'll need to use a grounded locknut, or a connector LISTED for that purpose.

Andrew
 
Conductors are THHN.

Looks like there are conflicting opinions as to whether or not a bushing / EGC is necessary. Anyone have other thoughts?
 
standard locknuts and bushing will not suffice and bonding type fittings would be needed:
(a) on conduits containing service conductors
(b) on circuits > 250 v to ground where concentric or ecentric knockouts are encountered (unless the enclosure listing accepts)
(c) where necessary to bind loosely joined raceways.

Take into account the Code is the minimim rrquirement.
 
A grounded bushing would need to be used if there are concentrics where the conduit terminates. The ground wire from the bushing to the ground lug would be sized according the feeder size, just as if you were to run an EGC (equipment grounding conductor).
If there are no concentrics, you'll need to use a grounded locknut, or a connector LISTED for that purpose.

Andrew

As Augie stated in his post, for a voltage under 250 volts, even with concentric KO's, bonding bushings or locknuts would not be required.
 
Conductors are THHN.

Looks like there are conflicting opinions as to whether or not a bushing / EGC is necessary. Anyone have other thoughts?

Just don't lose sight of the purpose of equipment grounding, to be an effective fault path that enables the operation of OCPD's (preferably instantaneous). If a poor fault path exists the operation of OCPD's may not function. Equipment grounding should never be assumed rather it should be intentionally & specifically known and installed.
 
As Augie stated in his post, for a voltage under 250 volts, even with concentric KO's, bonding bushings or locknuts would not be required.

That's right, I forgot about that. Can anyone post the code reference to this? I was looking for it the other day with no success.

Thanks!

Andrew
 
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