Multi Wire Branch Circuit

[jbolen]

I do not have code book available. I need to know what section of the NEC that states not install all the conductors of the same phase in one conduit.

example: All A-PHASE IN 1ST CONDUIT
All B-PHASE IN 2ND CONDUIT
ETC.
ETC.

 

[charlie b]

300.3(B)(1). There is an exception related to non-metalic raceway run underground.

But I am confused by your thread's title. I don't normally think of a multi-wire branch circuit being rated high enough to warrant parallel conductors. May I ask what the load is?

 

[Cavie]

I do not have code book available. I need to know what section of the NEC that states not install all the conductors of the same phase in one conduit.

example: All A-PHASE IN 1ST CONDUIT
All B-PHASE IN 2ND CONDUIT
ETC.
ETC.

You wont find it. It's not there. What you don't do is install the conductors of the same phase on the same neutral conductor.

 

[jbolen]

Multi Wire Branch Circuit -revised

Multi Wire Branch Circuit -revised

OK I'm in Afganistan on a job site.....I need to do a report....the folks here on the job site have install all of A-PHASE one pvc conduit all of B-PHASE in a PVC conduit and ALL THE NEUTRALS in a PVC conduit.......all seperate conduits.

I do not have code book available to qoute article.

 

[Smart $]

OK I'm in Afganistan on a job site.....I need to do a report....the folks here on the job site have install all of A-PHASE one pvc conduit all of B-PHASE in a PVC conduit and ALL THE NEUTRALS in a PVC conduit.......all seperate conduits.

I do not have code book available to qoute article.

As charlie said, it is permitted if the conduit runs are underground in close proximity.

300.3 Conductors.
...
(B) Conductors of the Same Circuit. All conductors of
the same circuit and, where used, the grounded conductor
and all equipment grounding conductors and bonding conductors
shall be contained within the same raceway, auxiliary
gutter, cable tray, cablebus assembly, trench, cable, or
cord, unless otherwise permitted in accordance with
300.3(B)(1) through (B)(4).
(1) Paralleled Installations. Conductors shall be permitted
to be run in parallel in accordance with the provisions
of 310.10(H). The requirement to run all circuit conductors
within the same raceway, auxiliary gutter, cable tray,
trench, cable, or cord shall apply separately to each portion
of the paralleled installation, and the equipment grounding
conductors shall comply with the provisions of 250.122.
Parallel runs in cable tray shall comply with the provisions
of 392.10(M).
Exception: Conductors installed in nonmetallic raceways
run underground shall be permitted to be arranged as isolated
phase installations. The raceways shall be installed in
close proximity, and the conductors shall comply with the
provisions of 300.20(B)....

300.20 Induced Currents in Ferrous Metal Enclosures
or Ferrous Metal Raceways.
...
(B) Individual Conductors. Where a single conductor
carrying alternating current passes through metal with magnetic
properties, the inductive effect shall be minimized by
(1) cutting slots in the metal between the individual holes
through which the individual conductors pass or (2) passing
all the conductors in the circuit through an insulating wall
sufficiently large for all of the conductors of the circuit.
Exception: In the case of circuits supplying vacuum or
electric-discharge lighting systems or signs or X-ray apparatus,
the currents carried by the conductors are so small
that the inductive heating effect can be ignored where these
conductors are placed in metal enclosures or pass through
metal.

FPN: Because aluminum is not a magnetic
metal, there will be no heating due to hysteresis; however,
induced currents will be present. They will not be of sufficient
magnitude to require grouping of conductors or special
treatment in passing conductors through aluminum
wall sections.​