Keeping up with the requirements of the Code should be the goal of everyone involved in electrical safety. Here is this month's newsletter with what I feel is an important rule in the 2017 NEC^®, complete with graphics and a video. I encourage you to use it as a training resource for your organization, and share it with your colleagues.

The content below is extracted from Mike Holt's Understanding the 2017 National Electrical Code^®, Volume 1.
Any underlined text denotes a change to the Code for the 2017 NEC.

(A) General. Equipment grounding conductors of the wire type must be sized not smaller than shown in Table 250.122, based on the rating of the circuit overcurrent protection device; however, the circuit equipment grounding conductor isn’t required to be larger than the circuit conductors. ▶Figure 250–232 and ▶Figure 250–233

▶Figure 250–232 ▶Figure 250–233

(B) Increased in Size. If ungrounded conductors are increased in size for any reason from the minimum size that has sufficient ampacity for the intended installation before the application of any adjustment or correction factor(s), wire-type equipment grounding conductors must be at least proportionately increased in size according to the circular mil area of the ungrounded conductors.

Example: If the ungrounded conductors for a 40A circuit (with 75ºC terminals) are increased in size from 8 AWG to 6 AWG due to voltage drop, the circuit equipment grounding conductor must be increased in size from 10 AWG to what size? ▶Figure 250–234 Solution: The circuit equipment grounding conductor must be increased to size 8 AWG. Conductor Size = 10,380 Cmil × 1.59 Conductor Size = 16,504 Cmil ▶Figure 250–234 Answer: The circuit equipment grounding conductor must be increased to 8 AWG [Chapter 9, Table 8]. The circular mil area of 6 AWG is 59 percent more than 8 AWG (26,240 Cmil/16,510 Cmil) [Chapter 9, Table 8]. According to Table 250.122, the circuit equipment grounding conductor for a 40A overcurrent protection device will be 10 AWG (10,380 Cmil), but the circuit equipment grounding conductor for this circuit must be increased in size by a multiplier of 1.59.

(C) Multiple Circuits. When multiple circuits are installed in the same raceway, cable, or cable tray, one equipment grounding conductor sized in accordance with 250.122, based on the rating of the largest circuit overcurrent protection device is sufficient. ▶Figure 250–235 and ▶Figure 250–236

▶Figure 250–235 ▶Figure 250–236

(D) Motor Branch Circuits.
(1) General. The equipment grounding conductor of the wire type must be sized in accordance with Table 250.122, based on the rating of the motor circuit branch-circuit short-circuit and ground-fault overcurrent protection device, but this conductor isn’t required to be larger than the circuit conductors [250.122(A)]. ▶Figure 250–237

▶Figure 250–237

Example: What size equipment grounding conductor of the wire type is required for a 14 AWG motor branch circuit [430.22], protected with a 2-pole, 30A circuit breaker in accordance with 430.22 and 430.52(C)(1)? ▶Figure 250–238 ▶Figure 250–238 Answer: The equipment grounding conductor isn’t required to be larger than the 14 AWG motor branch circuit conductors [250.122(D) (1) and 250.122(A)].

(F) Parallel Runs. If circuit conductors are installed in parallel as permitted by 310.10(H), an equipment grounding conductor must be installed for each parallel conductor set in accordance with the following:

(1) Raceways or Cable Trays.

(a) Parallel Feeder Runs in a Single Raceway or Cable Tray. The single wire‑type equipment grounding conductor is required in each raceway or cable tray. It must be sized in accordance with Table 250.122, based on the rating of the circuit overcurrent protection device.

(b) Parallel Feeder Runs in Multiple Raceways. The equipment grounding conductor in each parallel run raceway must be sized in accordance with Table 250.122, based on the rating of the feeder overcurrent protection device. ▶Figure 250–239 and ▶Figure 250–240

(2) Parallel Feeder Runs Using Multiconductor Cables.

(a) Multiconductor cables used in parallel must have the equipment grounding conductors of all cables electrically paralleled with each other.

▶Figure 250–239 ▶Figure 250–240

(b) Parallel multiconductor cables in a single raceway or cable tray are permitted to have a single equipment grounding conductor connected to the equipment grounding conductors within the multiconductor cables. This single equipment grounding conductor must be sized in accordance with 250.122, based on the rating of the feeder overcurrent protection device.

(c) Equipment grounding conductors installed in cable trays must comply with 392.10(B)(1)(c).

(d) Parallel multiconductor cables not installed in a raceway or cable tray must have an equipment grounding conductor of the wire type in each cable sized in accordance with 250.122, based on the rating of the circuit overcurrent protection device. ▶Figure 250–241

(G) Feeder Tap Conductors. Equipment grounding conductors for feeder taps must be sized in accordance with Table 250.122, based on the ampere rating of the overcurrent protection device ahead of the feeder, but in no case is it required to be larger than the feeder tap conductors. ▶Figure 250–242

▶Figure 250–241 ▶Figure 250–242

We'd love to hear from you about this series, and the ways you're using it. Send us your comments and feedback by clicking on Post a Comment below. Look out for the next part in this series a month from now, and please share with your colleagues.

This content is extracted from Mike Holt's Illustrated Guide to Understanding the 2017 National Electrical Code, Volume 2 textbook.
To review or catch up on previous newsletters on the National Electrical Code click here.

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