2023 NEC Article 210
A branch circuit is the last stretch of wiring before the outlet, so most of what building occupants touch is governed by Article 210. This lesson concentrates on the parts that change most from house wiring to commercial work: ground-fault protection in places other than dwelling units, arc-fault protection in the few commercial spaces where it applies, circuit ratings and continuous loads, the outlets that a commercial building must provide, and multiwire circuits. The figure shows a small community building with a serving kitchen, marked to show where GFCI protection is required.
Section 210.8 requires a listed Class A GFCI, installed in a readily accessible location. For places other than dwelling units, 210.8(B) applies to 125-volt through 250-volt receptacles on single-phase circuits rated 150 volts or less to ground and 50 amperes or less, and on three-phase circuits rated 150 volts or less to ground and 100 amperes or less. Distances to a sink or similar item are measured along the shortest path the power cord would follow without going through a floor, wall, ceiling, or fixed barrier. So an outlet just on the other side of a wall from a sink is not within 6 feet in the Code's sense, even though a tape measure says so.
The list has fifteen items. In plain terms, GFCI protection is required for receptacles in these places:
Rooftop receptacles do not have to be readily accessible except from the rooftop. A few relief provisions exist for industrial establishments under qualified supervision, using an assured equipment grounding conductor program, and listed weight-supporting ceiling receptacles for luminaires or fans may omit GFCI, though a general-purpose convenience receptacle built into a luminaire or fan needs it.
In the community building in the figure, every receptacle in the two restrooms and the kitchen is protected, as are the serving counter outlets (the steam table gives it permanent provisions), the patio outlet, the rooftop outlet, and the janitor closet outlet near the mop sink. The office is the useful case. Its sink makes any receptacle within 6 feet of the bowl edge a GFCI location, while a receptacle on the opposite wall is not on the list. The multipurpose hall has no sink and no cooking, so its convenience receptacles are not 210.8(B) locations. An owner may choose to protect them anyway, which is permitted.
Section 210.8(D) adds GFCI protection for the branch circuit or outlet supplying certain appliances rated 150 volts or less to ground and 60 amperes or less: automotive vacuum machines, drinking water coolers and bottle fill stations, high-pressure spray washers, tire inflation machines, vending machines, sump pumps, dishwashers, electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and microwave ovens. The text is not limited to dwellings. Section 210.8(E) requires GFCI protection for the servicing receptacles that 210.63 requires, described below.
Arc-fault protection reaches only a few commercial spaces. Under 210.12(D), 120-volt, single-phase, 10-, 15-, and 20-ampere branch circuits serving outlets or devices in hotel and motel guest rooms and suites, in areas used exclusively as patient sleeping rooms in nursing homes and limited-care facilities, and in sleeping quarters of fire, police, ambulance, rescue, and ranger stations need AFCI protection. Section 210.12(C) covers dormitory units. If branch-circuit wiring in those areas is modified, replaced, or extended, 210.12(E) requires protection too, except for an extension of no more than 6 feet that adds no outlets or devices other than splices. Hotel, motel, and assisted-living guest rooms with permanent cooking provisions follow the dwelling-unit branch circuit rules under 210.17.
A continuous load runs 3 hours or more. Under 210.20(A), the overcurrent device must be rated for at least the noncontinuous load plus 125 percent of the continuous load, and 210.19(A)(1) applies the same 125 percent to the conductor ampacity. If the assembly with its overcurrent devices is listed for 100 percent operation, the plain sum of the two loads is enough. A worked example: a store lighting circuit carries 14 amperes of continuous load and 2 amperes of noncontinuous load. The minimum is 2 + (1.25 x 14) = 19.5 amperes, so the smallest common breaker that works is 20 amperes, and the conductor and its terminals must carry at least 19.5 amperes. Turned around, a 20-ampere breaker that is not 100 percent rated can serve no more than 16 amperes continuous.
A single receptacle on its own circuit must be rated at least as high as the circuit (210.21(B)(1)). On a circuit with two or more receptacles, Table 210.21(B)(3) lets a 20-ampere circuit use 15- or 20-ampere receptacles, and Table 210.21(B)(2) limits the total cord-and-plug load a receptacle may serve: 12 amperes on a 15-ampere receptacle, 16 on a 20-ampere receptacle, and 24 on a 30-ampere receptacle.
Commercial occupancies have their own required outlets. Section 210.62 requires at least one 125-volt, 15- or 20-ampere receptacle within 18 inches of the top of each show window, with no point along the top more than 6 feet from an outlet. Section 210.63 requires a 125-volt, 15- or 20-ampere receptacle in an accessible location within 25 feet of heating, air-conditioning, and refrigeration equipment, on the same level, not connected to the load side of the equipment's disconnect. For other than one- and two-family dwellings, an indoor service equipment room or an indoor equipment room that needs dedicated space must have a receptacle in the same room or area. Section 210.65 covers meeting rooms of 1000 square feet or less, requiring wall outlets under 210.52(A)(1) through (A)(4), plus a floor outlet when a floor dimension is 12 feet or more and the area is at least 215 square feet, one per 215 square feet or fraction, at least 6 feet from any fixed wall. Auditoriums, schoolrooms, and coffee shops are not meeting rooms. Section 210.70(B) requires a wall-control-switched lighting outlet in every habitable room and bathroom of a hotel or motel guest room, and 210.70(C) requires a switched lighting outlet in attics, underfloor spaces, utility rooms, and basements used for storage or containing equipment.
A multiwire branch circuit has two or more ungrounded conductors that share a grounded (neutral) conductor, as in a 208Y/120 V system where three circuits share one neutral. All its conductors must originate at the same equipment, and each such circuit needs a means to disconnect all ungrounded conductors simultaneously at the point of origin (210.4(B)). It may supply only line-to-neutral loads, with exceptions for a single piece of utilization equipment or where all the ungrounded conductors are opened at once by the overcurrent device (210.4(C)). The ungrounded and grounded conductors must be grouped together under 200.4(B), for example with a wire tie, so a technician can tell which neutral belongs to which circuits.
In the field
During a rehab of a church hall, an electrician adds a coffee counter with a small sink and puts the new receptacle on an existing 20-ampere hall circuit. The inspector checks two things. First, the sink is within 6 feet along the cord path, so that receptacle needs GFCI protection, even though the rest of the hall does not. Second, the counter's urn and warmer will run for hours, so the load is continuous, and the circuit must be checked against the 125 percent rule before another appliance goes on it.
1. A small restaurant's kitchen has 125-volt, single-phase receptacles on 20 A circuits. Under 210.8(B), these receptacles:
2. A church fellowship hall has a break room sink. A receptacle is on the same wall 4 ft from the sink bowl edge. Under 210.8(B)(7), that receptacle:
3. A receptacle in a Group B office is 4 ft from a sink in a straight line, but the receptacle is on the other side of a solid wall from the sink. The shortest cord path is 15 ft around the wall. Under 210.8, this receptacle:
4. A mechanic's service bay at a fleet garage has 125-volt, single-phase, 20 A receptacles. Under 210.8(B), which listed location names service bays specifically?
5. A car dealership's vehicle showroom has 125-volt, 20 A wall receptacles supplied by single-phase circuits. Under 210.8(B)(10), the showroom receptacles:
6. A rooftop mechanical unit has a 125-volt, 15 A service receptacle on a single-phase circuit. Which statement is correct under 210.8(B) and 210.63?
7. A store's lighting circuit carries 12 amperes of continuous load and 5 amperes of noncontinuous load on a breaker not listed for 100 percent operation. Under 210.20(A), the minimum overcurrent device rating is:
8. A 20 A branch circuit with a standard (not 100 percent rated) breaker supplies a continuous load in a retail store. What is the maximum continuous load it can serve?
9. A receptacle rated 20 A is one of several receptacles on a 20 A circuit in a workshop. Table 210.21(B)(2) limits the total cord-and-plug load the receptacle may serve to:
10. Two rooms in a hotel: a guest room, and a 12 ft by 16 ft meeting room of 192 sq ft. Under 210.12(D), AFCI protection is required for 120 V, 15 and 20 A branch circuits serving:
11. An electrician extends a branch circuit in a hotel guest room by 4 ft to add an outlet for a lamp. Under 210.12(E), AFCI protection for the extended circuit is:
12. The show window of a strip mall store is 14 ft wide. Under 210.62, receptacle outlets must be installed so that no point along the top of the window is farther than what distance from an outlet?
13. A meeting room is 20 ft by 30 ft (600 sq ft) in an office building. Under 210.65(B)(2), how many floor outlets are required at least 6 ft from any fixed wall?
14. Three 20 A circuits in a 208Y/120 V three-phase office panel share a single neutral conductor and run in one raceway. What must the arrangement provide at the panel under 210.4(B)?