Paralleled Conductor Tap

[hochwire]

Here is the situation: 600A breaker with paralleled 500MCM conductors, 3 - 500's each in 3" conduits both conduits go to a common pull/j-box, i need to tap the feeder for a temporary 300A panel can i tap just one set the 500's?

 

[spsnyder]

I don't think so....

The paralleled conductors in each phase, polarity, neutral, or grounded circuit conductor shall comply with all of the following:
(1) Be the same length
(2) Have the same conductor material
(3) Be the same size in circular mil area
(4) Have the same insulation type
(5) Be terminated in the same manner


I don't think a tap in one set meets 5. Intuatively, you no longer split the load evenly between the two conductors which is the intent of length, size, material etc.

 

[petersonra]

Here is the situation: 600A breaker with paralleled 500MCM conductors, 3 - 500's each in 3" conduits both conduits go to a common pull/j-box, i need to tap the feeder for a temporary 300A panel can i tap just one set the 500's?

No. The conductors with the extra tap would be terminated differently, and the code would not permit that.

310.4 Conductors in Parallel.
...
The paralleled conductors in each phase, polarity, neutral,
or grounded circuit conductor shall comply with all of
the following:
...
(5) Be terminated in the same manner

As a practical matter, all the current for the new feeder would be coming through a single set of conductors that would still have to be able to carry the regular load, so they would be overloaded.

Is there room in the pull box for a distribution block?