Grounds in parallel feeders

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wired1

Member
Location
Louisiana
On a project we are working on the site work contractor cut into one conduit of a 350' underground parallel 400 amp feeder that was installed years ago. The general contractor has asked us to make the repairs.
We have repaired the conduit and upon pulling the old feeder out discovered that the #6 equipment ground installed with the 3/0 awg. phase conductors is to small. It should be # 3 awg. per my calculations.
The owner, contractor and all liable parties have understood this.
However I am having a hard time convincing them and am I correct in saying that we must also now pull out other parallel feeder (which is undamaged) because 310-4 states that all conductors must be of the same size circular mil area.

Is there an exception that I am maybe missing ?
I am refusing to repull the damaged feeder unless they approve repulling the second feeder.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
For parallel raceways the EGC in each raceway is based on the size listed in table 250.122. That size is also based the ampacity of the OCPD protecting the feeder. The EGC does not have to be the same size as the phase conductors and is not required to be larger than the phase conductors.
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
For a 400 amp circuit, the EGC has to be #3 minimum. If you run the circuit using two parallel 3/0 sets (ampacity 200 amps each, total ampacity 400), then each conduit needs a #3. So if the undamaged conduit contains a #6 EGC, then that EGC must be replaced with a #3.

That was a long way to say, "I agree with you."
 

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
Is there some way in which that would make a difference? Just curious as to where you are going with that question.

Probably wondering if RMC (or any other 250.118 compliant raceway) was used and the wire type EGC is redundant and could simply be pulled out.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
do the rules for parallel conductors require the minimum size be at least 1/0 for each conduit

Here's the general rule for parallel conductors. You'll see that EGC's are not on the list. Also look at 310.4(E).

310.4 Conductors in Parallel.
(A) General. Aluminum, copper-clad aluminum, or copper conductors of size 1/0 AWG and larger, comprising each phase, polarity, neutral, or grounded circuit conductor shall be permitted to be connected in parallel (electrically joined at both ends).
 
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