Major appliance circuits

The largest individual loads in most houses are fixed and cord-connected appliances: ranges, cooktops and ovens, clothes dryers, water heaters, dishwashers, microwaves, and pumps. Each has its own requirements for circuit rating, conductor size, connection method and disconnecting means, and many are continuous loads or have demand factors that change how they are counted. Lesson 5 covered the receptacle circuits of kitchens, bathrooms and laundries; this lesson covers the appliances themselves, reading their nameplates, sizing their circuits, connecting them correctly, and the special case of appliances supplied at 208 V in apartment buildings.

Reading the nameplate

Every appliance has a nameplate or rating label giving its voltage, power or current, and often the minimum circuit ampacity and maximum overcurrent protection. The installation instructions, which are part of the appliance's certification or listing, may add requirements such as a specific breaker size or receptacle type. Codes require installation according to the listing, so the instructions are as binding as the code itself.

Ranges, cooktops and ovens

Cooking appliances are large but rarely run at full power for long, so the codes apply demand factors in the load calculation (Lesson 1) and allow circuits smaller than the full nameplate rating would suggest.

In the US, the NEC (Table 220.55) permits a demand of 8 kW for a single household range rated not over 12 kW, and the range branch circuit must be at least 40 A for ranges of 8¾ kW or more (210.19(A)(3)). A counter-mounted cooktop and up to two wall ovens in the same room may be added together and treated as one range. Ranges connect through a 14-50R receptacle (four-wire) or are hard-wired.

Induction cooktops are increasingly common. Their electronics draw nearly sinusoidal current at a high power factor, and some can share power between zones, limiting their maximum draw. They may specify a 40 A or 50 A circuit; the instructions decide.

Clothes dryers

Electric dryers are 240 V appliances of about 5 kW, with motors and controls at 120 V, so they need both legs and a neutral.

• Circuit: 30 A, 240 V with 10 AWG copper.
• Connection: a four-wire receptacle (NEMA 14-30R) with two ungrounded conductors, a neutral and a separate bonding (grounding) conductor. Older installations used three-wire receptacles (10-30R) in which the frame was connected to the neutral; new installations use four wires so that a broken neutral cannot leave the frame energized.
• Venting: dryers produce lint and heat; their ducts are separate from electrical concerns but affect where the receptacle is placed.

In the NEC load calculation, a dryer is counted at the larger of 5,000 W or its nameplate rating (220.54), with demand factors for multiple dryers.

Heat-pump dryers use far less energy and some run on 120 V, 15 A or 20 A circuits; combination washer-dryers vary. Again, the instructions decide.

Water heaters

Electric storage water heaters typically have two 3.8 kW or 4.5 kW elements, wired so that only one heats at a time, at 240 V. They can run for hours after a large hot-water draw, so they are treated as continuous loads.

Heat-pump water heaters use roughly a third of the energy of resistance heaters, often with a backup element; some models run on 120 V. Tankless electric water heaters, by contrast, draw very large currents (often 100 A to 150 A at 240 V) for short periods, and can be impractical on a typical 100 A or 200 A service without load management (Lesson 10).

The NEC (422.13) treats fixed storage water heaters of 450 L (120 gal) or less as continuous loads, requiring branch-circuit ratings of at least 125% of the nameplate.

Dishwashers, disposals and other kitchen appliances

• Dishwashers: usually a 15 A or 20 A, 120 V individual circuit, either hard-wired through a junction box at the appliance or cord-and-plug connected to a receptacle in an adjacent cabinet. Their heating elements and pumps make them significant loads.
• Food waste disposers: a 15 A or 20 A, 120 V circuit, often switched from a wall switch near the sink, and sometimes sharing a split circuit with the dishwasher.
• Built-in microwaves and microwave-range hoods: typically a 15 A or 20 A individual circuit, since a microwave alone can draw 12 A to 15 A.
• Refrigerators and freezers: commonly an individual 15 A circuit, so that a fault elsewhere does not spoil food; ground-fault and arc-fault requirements for these receptacles vary by code and edition.

The NEC (210.8(D)) requires GFCI protection for dishwasher outlets in dwellings, and recent editions extend GFCI protection to all 125 V to 250 V kitchen receptacles serving countertops and to many appliance outlets; AFCI protection applies to kitchen circuits as well.

Laundry, pumps and other appliances

• Washing machines: a 20 A, 120 V circuit (often required to serve only laundry outlets), with GFCI protection required in laundry areas in many editions.

The NEC (210.11(C)(2)) requires at least one 20 A branch circuit for laundry receptacle outlets, serving no other outlets.

• Sump pumps: an individual circuit, so that other loads tripping a breaker do not stop the pump during a storm. GFCI protection may be required in basements and unfinished areas, which raises the risk of a nuisance trip disabling the pump; a high-water alarm on a separate circuit or battery is a good addition.
• Well pumps: 240 V circuits sized from the pump's motor data, with a pressure switch and often a controller; voltage drop over long runs to the well can be significant (Lesson 5).
• Hot tubs and spas: large 240 V loads with ground-fault protection, an emergency shutoff within sight but at a minimum distance from the tub, and bonding requirements (ELEC-120).

Disconnects and cord connections

Every fixed appliance needs a way to disconnect it for service:

• A plug and receptacle serves as the disconnect for cord-connected appliances if it is accessible.
• For hard-wired appliances, the branch-circuit breaker serves if it is within sight of the appliance or can be locked in the open position; otherwise a separate disconnect switch is installed at the appliance.
• Some appliances, such as furnaces and air conditioners, have their own specific disconnect rules (Lesson 8).

Cords supplied with appliances must not be replaced with longer or lighter cords, and appliance cords must not be run through walls or ceilings; if the receptacle is too far away, a new receptacle is installed.

Appliances at 208 V

Many apartment and condominium buildings are supplied from a three-phase 120/208 V system, so each unit gets two phases of a wye, with 208 V between them rather than 240 V. Appliances rated for 240 V run at 208 V with reduced output for resistive elements (75% of rated power) and possibly incorrect operation of motors and controls. Most ranges, dryers and water heaters are dual-rated (240/208 V); others must be ordered for 208 V. EV chargers, heat pumps and induction cooktops must be checked for their 208 V performance.