Parallel service conductors

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augie47

augie47

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State Electrical Inspector (Retired)
I have gone back and read previous posts until I have confused myself (easy to do), so I have to beat this dead horse again.:smile:
Situation: 1200 amp service (with main)
PVC conduits undergroud. Contractor elects to istall all of phase A in one conduit, etc. 4 wires per conduit
No metallic enclosures, fittings etc. so, I believe, 300.4(B)(3)allows the install.
However, from reading past postings, derating still applies so 350 kcmil x 4 x .80 = 1120, so we have a violation.

Had we run each phase per conduit, with neutral considered a non CC conductor, no problem.

Is my thinking correct ?
 
I was afraid of that.
I'm going to have one unhappy contractor.
 
possibly. but I'm 64 and no one has met my price yet :grin:
how much does a private carribean island with estate go for ?
 
augie47 said:
I have gone back and read previous posts until I have confused myself (easy to do), so I have to beat this dead horse again.:smile:
Situation: 1200 amp service (with main)
PVC conduits undergroud. Contractor elects to istall all of phase A in one conduit, etc. 4 wires per conduit
No metallic enclosures, fittings etc. so, I believe, 300.4(B)(3)allows the install.
However, from reading past postings, derating still applies so 350 kcmil x 4 x .80 = 1120, so we have a violation.

Had we run each phase per conduit, with neutral considered a non CC conductor, no problem.

Is my thinking correct ?
Click to expand...

What if it is the same situation except for no main and around 1000A or so connected load?
 
As far as I am concerned, if you told me "around 1000" :smile: I would say "no". If you provided documentation on a load at less than 1120 amps, it would be acceptable (relunctantly so, to me), but I'd like you to hear others input and not base any decision on my thoughts.
 
augie47 said:
I was afraid of that.
I'm going to have one unhappy contractor.
Click to expand...

It sounds like the quick fix is to just reidentify the conductors(ABCN in each conduit) and land them on the appropriate terminations if they're still long enough. Assuming they're the same length;)
 
It's a violation to place all of phase A in the same conduit. Should have three phases and grounded conductor in each conduit.
And 350 kcmil copper is 310 amps @ 75 ampacity. 4 X 310 = 1240. (OK 350@ 90, so 350 X 4 = 1400 and derated if required, remembering 75 deg terminations)
Assuming ?? balanced load this is OK.
Correct the parallel runs and all should be OK.
 
jimman said:
It's a violation to place all of phase A in the same conduit.
Should have three phases and grounded conductor in each conduit.
Click to expand...
code reference, please
jimman said:
And 350 kcmil copper is 310 amps @ 75 ampacity. 4 X 310 = 1240. (OK 350@ 90, so 350 X 4 = 1400 and derated if required, remembering 75 deg terminations)
Click to expand...
if the condcutors are grouped by phase the 1400 become 1120
jimman said:
Assuming ?? balanced load this is OK.
Correct the parallel runs and all should be OK.
Click to expand...

If it's still possible
 
jimman said:
It's a violation to place all of phase A in the same conduit. Should have three phases and grounded conductor in each conduit.
Click to expand...


What about 300.3(B)(1) exception, 300.3(B)(3), 300.5(I) exception 2?
 
augie47 said:
if the condcutors are grouped by phase the 1400 become 1120
Click to expand...

even if they aren't grouped by phase, you need to still derate...you can run individual conduits for each conductor, then no derating is needed...
 
Cow said:
It sounds like the quick fix is to just reidentify the conductors(ABCN in each conduit) and land them on the appropriate terminations if they're still long enough. Assuming they're the same length;)
Click to expand...

would you not consider the N as a CCC? will it not carry any current? not counted for derating?
 
emahler said:
would you not consider the N as a CCC? will it not carry any current? not counted for derating?
Click to expand...
Not when it's in a group with the phase conductors; that's what the discussion is about.
 
LarryFine said:
Not when it's in a group with the phase conductors; that's what the discussion is about.
Click to expand...

what's the load? linear or non linear? that helps define the situation, no?
 
Oops, didn't see those exceptions. Bear in mind that you may have to do some work on the enclosure, see 300.20 (B). Might get into listing trouble on that cabinet when you modify it. Typically don't see that arrangement. (for the issues listed above) Always good to learn.
 
emahler said:
what's the load? linear or non linear? that helps define the situation, no?
Click to expand...

The total load would need to be greater than 50% non-linear for the neutral to count as a CCC. IMO this is highly unlikely. So A-B-C-N in 4 conduits would work since no derating would be required.
 
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