Parallel service conductors

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augie47

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Location
Tennessee
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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 ?
 

augie47

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Location
Tennessee
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State Electrical Inspector (Retired)
I was afraid of that.
I'm going to have one unhappy contractor.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
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 ?
 

C3PO

Senior Member
Location
Tennessee
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 ?

What if it is the same situation except for no main and around 1000A or so connected load?
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
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.
 

Cow

Senior Member
Location
Eastern Oregon
Occupation
Electrician
augie47 said:
I was afraid of that.
I'm going to have one unhappy contractor.

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;)
 

jimman

Member
Location
North Carolina
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.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
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.
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)
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.

If it's still possible
 

C3PO

Senior Member
Location
Tennessee
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.


What about 300.3(B)(1) exception, 300.3(B)(3), 300.5(I) exception 2?
 

emahler

Senior Member
augie47 said:
if the condcutors are grouped by phase the 1400 become 1120

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...
 

emahler

Senior Member
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;)

would you not consider the N as a CCC? will it not carry any current? not counted for derating?
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
emahler said:
would you not consider the N as a CCC? will it not carry any current? not counted for derating?
Not when it's in a group with the phase conductors; that's what the discussion is about.
 

emahler

Senior Member
LarryFine said:
Not when it's in a group with the phase conductors; that's what the discussion is about.

what's the load? linear or non linear? that helps define the situation, no?
 

jimman

Member
Location
North Carolina
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.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
emahler said:
what's the load? linear or non linear? that helps define the situation, no?

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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