5.4 Grounded Conductors, Feeders, Outside Circuits & Surge Protection (Articles 200, 215, 225, 280, 285)
Key Takeaways
- Grounded conductors 6 AWG and smaller must have a continuous white or gray finish or three continuous white or gray stripes; 4 AWG and larger may instead be marked white or gray at each termination (NEC 200.6).
- A white or gray conductor re-identified for a switch loop may be used only as the supply to the switch, never as the return to the outlet (NEC 200.7(C)(1)).
- Feeder conductors must have an ampacity of at least the noncontinuous load plus 125 percent of the continuous load before any adjustment or correction factors are applied (NEC 215.2(A)(1)).
- A building supplied by a feeder needs a disconnecting means for all ungrounded conductors, located outside or inside nearest the point of entrance, with no more than six disconnects (NEC 225.31, 225.33).
- In the 2020 NEC, Article 285 covers surge-protective devices rated 1000 volts or less, and Article 280 covers surge arresters over 1000 volts.
Why this section matters
Articles 200 through 225 and 280 through 285 carry about three questions on the PSI outline. The branch-circuit rules (210) and load calculations (220) are in Sections 5.1, 5.2, 7.2, and 7.3. This section covers the rest: Article 200 (grounded conductors), 215 (feeders), 225 (outside branch circuits and feeders), and 280/285 (surge protection).
Identifying the grounded conductor (Article 200)
| Conductor size | Permitted identification (200.6) |
|---|---|
| 6 AWG and smaller | Continuous white or gray outer finish, or three continuous white or gray stripes along the length on insulation that is not green |
| 4 AWG and larger | Any of the above, or a distinctive white or gray marking encircling the conductor at each termination, applied at installation |
| Flexible cords | Methods in 400.22 |
More than one system in the same enclosure (200.6(D)): when grounded conductors of different systems share a raceway, box, or enclosure (for example, a 208Y/120 V neutral and a 480Y/277 V neutral), each system's grounded conductor must be identifiable. Typically one system uses white and the other gray, or white with a colored stripe that is not green. The method must be documented or posted.
Using white or gray for something else (200.7): generally prohibited, with exceptions:
- In a cable assembly, a white or gray conductor may be used as an ungrounded conductor if it is permanently re-identified (tape, paint, or other effective means) at every location where it is visible and accessible.
- In a switch loop, the re-identified white or gray conductor may be used only for the supply to the switch, never as the return conductor from the switch to the outlet (200.7(C)(1)).
Terminals and polarity (200.9-200.11): the identified terminal for the grounded conductor is whitish or silver in color. On screw-shell lampholders the shell connects to the grounded conductor. No grounded conductor may be attached to a terminal in a way that reverses the designated polarity.
Feeders (Article 215)
| Rule | 2020 NEC |
|---|---|
| Feeder conductor ampacity before adjustment or correction is at least the noncontinuous load plus 125% of the continuous load; after adjustment and correction it is at least the load served | 215.2(A)(1) |
| If a feeder carries the whole load of service conductors rated 55 A or less, the feeder ampacity may not be less than the service conductors' ampacity | 215.2(A)(3) |
| Feeder overcurrent device rated at least noncontinuous load plus 125% of continuous load, unless the assembly is listed for 100% operation | 215.3 |
| Ground-fault protection of equipment for feeder disconnects rated 1000 A or more on solidly grounded wye systems over 150 V to ground and not over 600 V phase-to-phase, unless provided on the supply side | 215.10 |
| Where premises have more than one nominal voltage system, each ungrounded feeder conductor must be identified by phase or line and system at every termination, connection, and splice point, and the method documented or posted | 215.12(C) |
Outside branch circuits and feeders (Article 225)
Article 225 covers overhead and underground circuits run outdoors between buildings or to outdoor equipment on the same premises.
Overhead clearances (225.18, 225.19): the same heights as overhead services in 230.24 (Section 7.1):
- 10 ft above pedestrian areas at 150 V or less to ground;
- 12 ft over residential property and driveways at 300 V or less to ground;
- 15 ft over those areas above 300 V;
- 18 ft over public streets, alleys, roads, and parking areas subject to truck traffic;
- 8 ft above roofs, with the same exceptions as services.
Washington adds a 3-ft roof clearance where the voltage between conductors is 300 V or less and the roof is guarded or isolated (WAC 296-46B-225).
Conductor size for overhead spans (225.6(A)): 10 AWG copper or 8 AWG aluminum for spans up to 50 ft; 8 AWG copper or 6 AWG aluminum for longer spans (600 V and less).
Supply and disconnects for a building:
- A building or structure is generally supplied by only one feeder or branch circuit (225.30). Exceptions include fire pumps, emergency and standby systems, and large capacity needs with permission.
- A disconnecting means must open all ungrounded conductors that supply or pass through the building (225.31(A)). It must be readily accessible, located outside or inside nearest the point of entrance of the conductors (225.31(B)).
- No more than six disconnects per supply, grouped (225.33).
- The disconnect must be suitable for use as service equipment, with limited exceptions (225.36).
- Washington treats a disconnect on the building, or within sight and within 15 ft of it, as "in the building" and requires a half-inch-letter identification plate (WAC 296-46B-225).
- Vegetation such as trees may not be used to support overhead conductor spans (225.26).
Grounding at the second building (250.32): each building needs its own grounding electrode system. A feeder to a separate building includes an equipment grounding conductor. The grounded (neutral) conductor is not bonded to the equipment grounding conductor at the second building's disconnect, except for certain existing installations with no parallel metallic paths.
Surge arresters and surge-protective devices (Articles 280, 285)
In the 2020 NEC:
- Article 280 covers surge arresters over 1000 V (utility and medium-voltage equipment).
- Article 285 covers surge-protective devices (SPDs) rated 1000 V or less. SPDs must be listed and marked with a short-circuit current rating, and may not be installed where the available fault current exceeds that rating.
| SPD type | Where it goes |
|---|---|
| Type 1 | Permanently connected. Intended for the line side of the service disconnect overcurrent device, between the service transformer secondary and the service equipment; also permitted on the load side |
| Type 2 | Permanently connected, on the load side of the service disconnect overcurrent device, including at branch panelboards |
| Type 3 | Point-of-utilization devices on the load side of branch-circuit overcurrent protection; where the manufacturer's instructions call for it, at least 30 ft of conductor length from the service or separately derived system disconnect (285.25) |
| Type 4 | Component SPDs, including those built into other equipment |
SPD leads should be kept as short as practicable and avoid unnecessary bends, because lead length adds let-through voltage. Dwelling services must have a Type 1 or Type 2 SPD integral to or immediately adjacent to the service equipment (230.67, Section 7.1).
A 3-conductor cable with black, red, and white conductors is used as a switch loop. How does NEC 200.7(C)(1) allow the re-identified white conductor to be used?
Under NEC 200.6(B), which identification method is allowed for a 2/0 AWG grounded conductor but not for a 10 AWG grounded conductor?
Where may a Type 2 surge-protective device be installed under NEC Article 285?