RMC requirement to be connected to grounding electrode

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xguard

Senior Member
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Baton Rouge, LA
I've seen rigid galvanized steel conduit be required to be connected to a ground rod where the rigid conduit transitions below ground and then the run changes to PVC. Is there an NEC requriement to do this? Is there any benefit to doing this?

EXAMPLE:

A typical installation would have the RMC bonded to a service disconnect. The RMC would then enter the ground (dirt, maybe concrete then dirt), be connected to a ground rod, then the run changes to PVC. The conduit contains an Equipment grounding concutor and neutral.

Typical Load side installatio - The PVC conduit mentioned above continues underground until it reaches a structure, the conduit run transitions back to RMC while still underground. The RMC is connected to a ground rod. The RMC is also bonded to a small panel or fused disconnect.

I can't see where the RMC connection to a ground rod is required by code or has any particular benifit. Thanks for any feedback.
 
The GEC would need to be bonded to both ends of the metallic ferrous raceway, not possible if you changeover to PVC mid run.
 
infinity said:
The GEC would need to be bonded to both ends of the metallic ferrous raceway, not possible if you changeover to PVC mid run.
Click to expand...

The GEC is actually in it's own pvc conduit at the service disconnect. The conduit that is also being bonded to the grounding electrode contains the feeder, not the GEC. There is a conduit clamp on the outside of the metal conduit that is conected to a bare solid conductor that goes to the ground rod.
 
250.80 (for services) and 250.86 (for other than services) require you to bond raceways. There is an exception for a metal elbow to not be bonded if it is isolated by non-metallic conduit. It almost sounds like someone (probably back in the day) didn't know about the exception or it didn't exist in older versions of the NEC and always drove a ground rod to "bond" the elbow. Obviously in your installation it is bonded through the RMC where it connects above ground but it could be a case where someone was taught to ground the elbow underground so that's how they always do it.


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