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Thursday, November 5, 2020
Question:
Hello Friends,
I see section 310.10 related to parallel conductors #1/0 AWG and larger where the same length, conductor material, cross-sectional circular mil area, and insulation in each phase should match. Where is the specific language that says for any branch circuit, all three-phase circuit conductors should be the same length, material, size, and insulation (equal leg circuit characteristics)? My example was only three-phase, but what if the circuit is complicated by a neutral conductor? Is it permitted to have unequal phase conductors and a 50% neutral conductor? My example is a single-phase 480V water heater circuit on a 40A circuit breaker with one used copper #8 and a used #6 aluminum both THW in the same conduit with a #10 AWG ground. Doesn't seem right. Is it a violation?
Vincent L Trejchel
A
Answer:
Hi Vincent,
Thanks for participating. If we understand your question correctly, you are asking of the single conductors of a branch circuit (not installed using parallel conductors in accordance with 310.10) have to be the same length. The answer is no. The ungrounded conductors and neutral conductor and equipment grounding conductor do not have to be the same length because these are the circuit conductors. The reduced neutral size may be allowed based on the load served. When multiple conductors are being installed in parallel to create one conductor (one conductive path) of higher capacity, then the rules in 310.10 for installing conductors in parallel apply.