Multi-Conductor Cable/Phase Calculator

In parallel cables, the phase current is divided between two or more conductors. Typically in paralleling cables, the size and length of each cable are the same, and the current flow is equally divided between the parallel conductors. If the conductors (or lengths) are of unequal size, then the current will not be distributed evenly (i.e. the conductors will carry different currents). Where currents in parallel conductors are unbalanced, it may be necessary to provide separate overload protection for each conductor.

Parallel conductor installations are covered in NEC 310 or CEC 12-108 and are permitted for each phase, polarity, neutral, or grounded conductor in sizes 1/0 AWG and larger. Joining conductors in parallel is like having two or more smaller conductors connected at each end to make one larger conductor.

In order to install conductors in parallel, the paralleled conductors in each phase, polarity, neutral, grounded circuit conductor, equipment grounding conductor, or equipment bonding jumper must comply with all of the following:

(1) Be the same length.

(2) Consist of 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.

The above rules ensure that each set of parallel conductors carries the same ampacity. Where run in separate cables or raceways, the cables or raceways must have the same number of conductors and must have the same “electrical characteristics”.

It is important to use the applicable national codes for your specific installation.

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