RUNNING PARALELL WIRES IN EMT

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Duke1317

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MAY I RUN 3-500KCMIL FOR ONE PHASE EXAMPLE:
3-4" EMT IN PARALELL WITH
PHASE A 3-500KCMIL 4" EMT
PHASE B 3-500KCMIL 4" EMT
PHASE C 3-500KCMIL 4" EMT
 
No you cannot have all of one phase in one conduit. There is an exception but it is with pvc conduit underground -- I believe

300.3(B)(1) said:
(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 392.20(C).
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).
Click to expand...
 
I might add that even if you do use PVC conduit, you have to make provisions in the event the conduits terminate in a metal enclosure.
In the event these are service conductors it would be a good idea to check with your POCO as some of them prohibit such installations.
 
There is a fairly recent thread where the OP had encountered just what you described - IIRC same raceway and conductor sizes even.

He had some heating issues at that install.
 
Here is a example of applying the exception Dennis mentioned.

Als_Isolated_Phase.JPG



While fine in PVC underground it isa no go with EMT.
 
Why is it OK with PVC?

A) Is it because the PVC will minimize the heat transfer and other combustable material touching the conduit will not be a fire hazard?

or

B) The magnetic heating is not an issue because the conduit is not metal?
 
:)


On longer posts I make more errors.. on that one I had a 50-50 chance.
 
edward said:
Why is it OK with PVC?

A) Is it because the PVC will minimize the heat transfer and other combustable material touching the conduit will not be a fire hazard?

or

B) The magnetic heating is not an issue because the conduit is not metal?
Click to expand...

Not only is it not metal, it is not steel. Aluminum conduit possibly would have some problems but not as much as a steel conduit.
 
Would there be any point in taking advantage of the PVC exception? Is it somehow easier run all of one phase in a conduit? (I mean some advantage besides having people who don't quite know what they are doing be able to 'get away with' a code compliant install).
 
jaggedben said:
Would there be any point in taking advantage of the PVC exception? Is it somehow easier run all of one phase in a conduit? (I mean some advantage besides having people who don't quite know what they are doing be able to 'get away with' a code compliant install).
Click to expand...

Typically it makes it easier to keep the paralleled conductors close to the same length and it makes it much easier to terminate.

Roger
 
Duke1317 said:
MAY I RUN 3-500KCMIL FOR ONE PHASE EXAMPLE:
3-4" EMT IN PARALELL WITH
PHASE A 3-500KCMIL 4" EMT
PHASE B 3-500KCMIL 4" EMT
PHASE C 3-500KCMIL 4" EMT
Click to expand...

Does the term "inductive heating" ring a bell?

Roger
 
jaggedben said:
Would there be any point in taking advantage of the PVC exception? Is it somehow easier run all of one phase in a conduit? (I mean some advantage besides having people who don't quite know what they are doing be able to 'get away with' a code compliant install).
Click to expand...

FWIW, for an existing duct bank, it allows you to avoid the need for all of the parallel raceways to be the same size.
 
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