11.5 Appliances, Electric Space Heating, Water Heaters & Special Equipment

11.5 Appliances, Electric Space Heating, Water Heaters & Special Equipment

Chapter 4 of the NEC governs equipment for general use, and NEC Chapter 6 governs special equipment. Both feed the Prov Special Occupancies and Equipment subject area. The rules below are the ones that determine whether an ordinary residential or light commercial installation passes inspection, and several of them are load-calculation inputs you already used in Chapter 5 of this guide.

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Appliances (Article 422)

Branch-Circuit Sizing (NEC 422.10)

The branch circuit for an individual appliance must have a rating not less than the marked rating of the appliance. Where the appliance is a continuous load, the branch circuit must be rated not less than 125 percent of the marked rating.

Water Heaters: The 120-Gallon Rule (NEC 422.13)

A fixed storage-type water heater having a capacity of 120 gallons or less shall be considered a continuous load for the purposes of sizing branch circuits.

This single sentence produces a very common exam calculation. A 4,500 VA, 240-volt residential water heater draws 18.75 A, but because it is a continuous load the branch circuit must be rated at:

$18.75\text{ A} \times 1.25 = 23.4\text{ A} \rightarrow \textbf{30-ampere circuit, 10 AWG copper}$

A 20-ampere circuit on 12 AWG is not compliant even though the running current is only 18.75 A. Note the boundary: the continuous-load classification is triggered by tank capacity of 120 gallons or less, not by wattage.

Overcurrent Protection (NEC 422.11)

A branch circuit supplying a single non-motor-operated appliance rated more than 13.3 amperes must have overcurrent protection not exceeding 150 percent of the appliance rating, with rounding to the next higher standard size permitted where 150 percent does not correspond to a standard rating. Appliances with a marked maximum overcurrent protective device rating must be protected at or below that marking.

Flexible Cord Connections (NEC 422.16)

Cord connection is permitted for specific appliances at specific lengths, measured from the back of the appliance to the face of the receptacle:

In every case the receptacle must be accessible and located to avoid physical damage to the cord, and the appliance must be provided with the grounding-type attachment plug. The receptacle for a dishwasher must be located in the space adjacent to the appliance space, not behind the dishwasher itself.

GFCI for Appliances (NEC 422.5)

Certain appliances rated 150 volts or less to ground and 60 amperes or less require GFCI protection regardless of location, including automotive vacuum machines, drinking water coolers and bottle-fill stations, high-pressure spray washing machines, tire inflation machines, vending machines, and sump pumps.

Disconnecting Means (NEC 422.30 through 422.35)

• Every appliance requires a disconnecting means that disconnects all ungrounded conductors.
• Permanently connected appliances rated over 300 VA (422.31(B)): the branch-circuit switch or circuit breaker may serve as the disconnect only where it is within sight from the appliance or is capable of being locked in the open position per 110.25.
• Cord-and-plug-connected appliances (422.33): a separable connector or an attachment plug and receptacle may serve as the disconnecting means. For a household electric range, a plug and receptacle behind the range is permitted to serve as the disconnect if it is accessible from the front by removing a drawer.
• Unit switches (422.34): a unit switch with a marked-off position that disconnects all ungrounded conductors may serve as the disconnect in a one-family dwelling, provided the service disconnect or branch-circuit device is also available.

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Fixed Electric Space-Heating Equipment (Article 424)

Continuous Load Classification (NEC 424.3(B))

Fixed electric space-heating equipment shall be considered continuous load.

Therefore the branch-circuit conductors and the overcurrent protective device must be sized at not less than 125 percent of the total heating load, including any associated blower motor. A 10 kW, 240-volt duct heater draws 41.7 A; the circuit must be rated:

$41.7\text{ A} \times 1.25 = 52.1\text{ A} \rightarrow \textbf{60-ampere circuit}$

Note the contrast with the load calculation side of the Code: in the standard dwelling calculation, space heating is compared against air conditioning under 220.60 and only the larger is counted, and in the optional calculation 220.82(C) applies a 65 percent or 40 percent factor. Those demand factors size the service. They never reduce the branch circuit to the heater itself, which is always 125 percent.

Other Article 424 Requirements

• Subdivided loads (424.22(B)): electric space-heating equipment with a load exceeding 48 amperes must be subdivided into circuits not exceeding 48 amperes, each protected at not more than 60 amperes.
• Disconnecting means (424.19): a means must be provided to simultaneously disconnect the heater, motor controller, and supplementary overcurrent devices, located within sight of the equipment or lockable in the open position.
• Heating cables (424 Part V): cables must not be installed in walls unless run vertically as a lead, must be separated at least 8 in. from the edges of outlet and junction boxes used for mounting surface luminaires, and must be kept 2 in. from metal raceways and other cables not part of the heating system.
• Clearances (424.36): heating cable in a ceiling must be separated at least 2 in. (50 mm) from the nearest edge of any recessed luminaire, trim, or ventilating opening.

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Specialty Equipment Articles

Elevators, Dumbwaiters, Escalators (Article 620)

• A disconnecting means for each elevator must be a lockable enclosed externally operable fused motor-circuit switch or circuit breaker, located within sight of the motor controller (620.51).
• Where more than one driving machine disconnecting means is supplied by a single feeder, the overcurrent devices must be selectively coordinated with all supply-side overcurrent devices (620.62).
• A single branch circuit is required to supply the elevator car lights, receptacle, auxiliary lighting, and ventilation, with the disconnect adjacent to the controller.

Electric Welders (Article 630)

Welder branch-circuit conductors are sized from the welder's duty cycle, because a welder that operates 30 percent of the time does not heat the conductors the way a continuous load does. Table 630.11(A) provides the multipliers applied to the rated primary current of an arc welder, ranging from 1.00 at 100 percent duty cycle down to roughly 0.45 at 20 percent duty cycle. Conductors for a group of welders may be further reduced under 630.11(B).

Electric Vehicle Supply Equipment (Article 625)

• Continuous load (625.41): EVSE and its overcurrent protection are a continuous load, so the branch circuit and the overcurrent device must be rated at not less than 125 percent of the equipment's nameplate rating. A 48-ampere EVSE therefore requires a 60-ampere circuit.
• Disconnecting means (625.43): for EVSE rated more than 60 amperes or more than 150 volts to ground, the disconnecting means must be lockable in the open position and installed in a readily accessible location.
• Personnel protection: EVSE must incorporate a listed personnel protection system against electric shock, and outdoor dwelling-unit EVSE outlets also fall under the 210.8(F) GFCI requirement.
• The 2023 NEC added 220.57 to address EVSE load calculations, permitting the load to be the nameplate rating or the maximum output of an energy management system that limits it.

Medical and Industrial X-Ray Equipment (Article 660)

Branch-circuit conductors for X-ray equipment are sized from the momentary rating or the long-time rating, whichever is greater, and a disconnecting means of adequate capacity for at least 50 percent of the momentary rating or 100 percent of the long-time rating, whichever is greater, must be provided in a location readily accessible from the X-ray control.