Feeder Upgrade with undersized equipment grounding conductor

[DAVE BRANT]

I have a 600 amp feeder (120/208V, 3 phase, 4 wire & ground) consisting of 2 sets of 350KCM conductors with #1 awg grounds run in 2 - 3 inch EMT conduits. I need to upgrade this feeder to 800 amps. I would like to add a 3rd set of 350KCM conductors with a #1/0 awg ground in a 3 inch conduit in parallel with the existing 2 sets. The existing #1 awg grounds will be undersized for an 800 amp feeder. Since the EMT conduit is also an "equipment grounding conductor -EGC" in parallel with the #1 awg ground conductor is it acceptable to re-use the existing #1 awg grounds? The code does not require a separate EGC to be installed in the conduits.

For practical purposes it seems as it this would be an acceptable arrangement.

 

[dkidd]

As silly as it is, you would have to remove the #1 and just use the raceway.

 

[jumper]

Strange as it may seem, no.

A wire type EGC, where used, must be full sized to T250.122.

250.122 Size of Equipment Grounding Conductors.
(A) General.
Copper, aluminum, or copper-clad aluminum
equipment grounding conductors of the wire type shall not
be smaller than shown in Table 250.122, but in no case
shall they be required to be larger than the circuit conduc-
tors supplying the equipment.

Since you said your EMT qualifies as an EGC, just eliminate the #1/0 wire EGC and you would be compliant. Code can be weird at times

 

[infinity]

Yup, use all full size EGC's or none at all.

 

[dkidd]

I have a 600 amp feeder (120/208V, 3 phase, 4 wire & ground) consisting of 2 sets of 350KCM conductors with #1 awg grounds run in 2 - 3 inch EMT conduits.

You could pull 4 500KCM in each of the 2 - 3" and use the EMT for the ground, or 4 500KCM and a #1/0 would be alright.