3 Phases a Grounded conductor and rigid (ocal )

Z

zooby

Senior Member
Location
Indiana
Occupation
maint. electrician
Scenario---Zoo built around 1986. Panel which powers ticket booths etc...PLUS the traffic signal [ yep...but that's how it is ] is down in a "vault" and has to be replaced due to condition.
This panel ( 120/208 3ph 4w ) is fed from one of our pad mounts a few hundred feet away. There is a fused disconnect for this panel back at the xfmr.
There are four conductors leaving the bottom of xfmr out to the panel/vault. I see no "ground" leaving with them.
I am confident this conduit run is RGC Ocal. I have seen this done out here in other areas that were dug up or remodeled and it does say this on the old plans.
There is a solid conductor coming from a ground rod at the vault which then connects to a bushing on the rigid...then to a bar in the panel.
So...Is the conduit considered the "ground"? I do get jumbled up in 250 with the correct terminology but is 250.64 (E) where this lands at? I fear not.
Thank you guys.
 
ptonsparky said:
I would say it is or could be considered an Equipment Ground. Has the neutral been bonded at the panel or is it floating? Are the solid conductors adequately sized for an EG, not as a GEC. (Larger than #6).
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The neutral is bonded at the panel. Nothing was done back at the transformer/ disconnect. You know sitting here I cannot say for certain but that solid conductor coming from the rod is pretty beefy. I have to get down in there again soon so I will give that a hard look. Sheesh...250 can mush up a guys brain but this is making me dive in more.
 
IDK when it changed but at one time that 4 wire may have been compliant, especially if the Rigid was not bonded at the fused disconnect.
It could be considered a Grounding Electrode. More than 10'.

Your AHJ should be able to voice an opinion about updating to current code or leave as is.

IMO, it's a can of worms waiting to be opened.
 
ptonsparky said:
IDK when it changed but at one time that 4 wire may have been compliant, especially if the Rigid was not bonded at the fused disconnect.
It could be considered a Grounding Electrode. More than 10'.

Your AHJ should be able to voice an opinion about updating to current code or leave as is.

IMO, it's a can of worms waiting to be opened.
Click to expand...
Thanks very much for your time!
 
The RMC is the EGC for the feeder. The panel at the separate structure requires a GES which is likely the ground rod with the solid conductor at the vault being the GEC for the panel. Sounds like this is done correctly.
 
infinity said:
The RMC is the EGC for the feeder. The panel at the separate structure requires a GES which is likely the ground rod with the solid conductor at the vault being the GEC for the panel. Sounds like this is done correctly.
Click to expand...
Thank you sir.....Appreciate it.
 
In 1986 this would been allowed to have the neutral bonded at the separate structure. Technically may been a violation to have the RMC bonded at both ends like described as it would have established a parallel path and put neutral current on the raceway.
 
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