How the 2017 NEC has changed things.
We’ve struggled for many years to comply with the requirements in Sec. 250.122(F) of the National Electrical Code (NEC) when routing multiconductor cables with equipment grounding conductors (EGCs) in parallel in cable tray. Prior to the 2017 NEC, if you had multiconductor cables in parallel and the cable contained an EGC, you were most likely in violation of the Code. Due to the impracticability of ordering custom cables with oversized EGCs, we’ve been left to either get Special Permission to use one large EGC in the cable tray or use the tray as an EGC in addition to utilizing the paralleled EGCs in the cables. But the 2017 NEC now provides relief for these cases.
Section 250.122(F)(2) of the 2017 Edition of the Code allows multiconductor cables with normal sized EGCs to be routed in parallel as long as the following conditions are met:
a) If multiconductor cables are installed in parallel, the EGC(s) in each cable shall be connected in parallel.
b) If multiconductor cables are installed in parallel in the same raceway, auxiliary gutter, or cable tray, a single EGC that is sized in accordance with 250.122 shall be permitted in combination with the EGCs provided within the multiconductor cables and shall all be connected together.
c) EGCs installed in cable trays shall meet the minimum requirements of Sec. 392.10(B)(1)(c). Cable trays complying with Sec. 392.60(B), metal raceways in accordance with Sec. 250.118, or auxiliary gutters shall be permitted as the EGC.
d) Except as provided in Sec. 250.122(F)(2)(b) for raceway or cable tray installations, the EGC in each multiconductor cable shall be sized in accordance with 250.122 based on the overcurrent protective device for the feeder or branch circuit.
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