Question: What are the rules for paralleling feeder conductors?
See the answer below.
Answer: Section 310.10(H) of the 2017 NEC states the conductors for each phase, polarity, neutral, or grounded circuit shall be permitted to be connected in parallel with the following restrictions:
- Conductors are 1/0 or larger
- Conductors are the same length
- Conductors are the same material
- Conductors are the same size
- Conductors have the same insulation type
- Conductors are terminated in the same manner
- When in separate cables or raceways the cables or raceways with conductors shall have the same number of conductors and have the same electrical characteristics
Explanation: These rules are meant to ensure each conductor in a paralleled set carries the same amount of current as the other conductors of the paralleled set.
Lupacchino is a senior design engineer with Gaylor Electric, Inc. in Noblesville, Ind. and serves as an alternate on NEC Code-Making Panel No. 3. He is currently licensed in more than 80 jurisdictions. He can be reached at [email protected].