Branch Circuit Voltage and Amperage Ratings

Multiple Outlet Branch Circuit Amperage and Voltage Rating Limits
1. Use only 15 amp and 20 amp, 120 volt, circuits for multiple outlet branch circuits. A multiple outlet branch circuit has more than one light fixture or receptacle on the same circuit. One duplex receptacle (the common receptacle with two openings for plugs) counts as two receptacles. A circuit that serves one duplex receptacle is a multiple outlet branch circuit. This provision does not apply to a circuit that serves one single receptacle or one single light fixture.
2. Use only 120 volt branch circuits to supply residential light fixtures, and to supply receptacles for plug-and-cord connected loads not more than (≤) 1,440 watt s, and to supply motor loads less than (<) .25 horsepower.
3. You may use either 120 or 240 volt branch circuits to supply one plug-and-cord connected or one permanently wired appliance rated more than (>) 1,440 watt s. This means that branch circuits rated more than (>) 120 volts are effectively limited to serving a single receptacle or permanently wired fixed appliances.
4. Determine the branch circuit amperage rating based on the rating of the lowest rated device in the circuit. Example: if the conductors are rated at 20 amps and a single receptacle is rated at 15 amps, the circuit is rated at 15 amps and should be protected by a 15 amp over-current device. Remember that either 15 or 20 amp receptacles may be used on a 20 amp multiple receptacle circuit. See Section 4002.
5. Do not supply common areas of a two-family building from the electrical supply serving either individual unit. Examples of such circuits include lights, security systems, and communication systems.


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Branch Circuits Required

Central Heating Branch Circuit
1. Provide a dedicated branch circuit to serve central heating appliances such as gas furnaces and heat pump air handlers. You may use this circuit to serve directly related equipment such as pumps, motorized valves and dampers, humidifi ers, and air fi lters.
2. Do not apply this rule to fi xed space heating appliances such as electric baseboard heaters. You may supply more than one space heating unit on a branch circuit.

Kitchen Receptacle Branch Circuit
1. Provide at least (≥) two 20 amp, 120 volt branch circuits to serve only countertop, wall, and floor receptacles in the kitchen, pantry, breakfast and dining areas, and similar rooms. You may not use these branch circuits to supply light fixtures or other outlets in the listed rooms and you may not use these branch circuits to supply outlets in rooms other than those listed.
2. You may use the kitchen receptacle branch circuit to serve an electric clock and to serve the electronics and lights on gas-fired ranges, ovens, and counter-mounted cooking appliances.
3. You may use a dedicated 15 amp branch circuit to provide power for a refrigerator or you may use the kitchen receptacle branch circuit. Read the full Topic

Feeder Load Calculation

Limitations of the Material in this Section
We do not recommend that most readers of this book determine feeder load. Leave this to experienced electrical contractors. For readers who are interested in how to calculate feeder loads, we provide the following explanation. Feeder wire sizes based on the formula in this section are for wires run to subpanels that do not serve all (100 percent) of the home’s electrical load. Use the electrical service formula to determine the feeder wire size for a feeder that serves the home’s entire electrical load.

Feeder Load Formula
1. Use the following table to determine the minimum size for the hot (ungrounded) feeder wires.
2. You are not required to make the hot (ungrounded) feeder wires larger than the service entrance wires.
3. Provide an equipment grounding wire in a feeder cable if the circuits served by the feeder require equipment grounding wires. This will apply in most cases. See also Section 3607. Read the full Topic

Multiwire Branch Circuits

Multiwire Branch Circuit Requirements
1. Originate multiwire branch circuit wires from adjacent slots on the same panelboard.
2. Use a two-pole over-current device or two single pole devices that are connected by an approved handle tie to simultaneously disconnect power to all ungrounded (hot) a multiwire branch circuit wires. Do not connect circuit breaker handles with nails, wires, or other unapproved handle tie substitutes.
3. Use wire ties or similar devices to group all ungrounded (hot) and grounded (neutral) wires of each multi-wire branch circuit in the cabinet where the circuit originates. This grouping is required in only one location.

Panelboard Protection and Rating

1. Use a panelboard with an ampacity rating at least (≥) as large as the rating of the wires that supply the panelboard. You may use a panelboard with a higher ampacity rating, but not one with a lower rating than the service entrance or feeder wires that supply the panelboard.
2. Protect panelboards using not more than (≤) 2 main circuit breakers or 2 sets of fuses with a combined rating not more than (≤) the panelboard’s maximum current rating. These circuit breakers or fuses will often be the service equipment in main panelboards. For subpanels, these circuit breakers or fuses may be at the main panelboard or in the subpanel.
3. Identify the purpose or function of all branch circuits in the panelboard. This identification should be permanent and legible and should be able to withstand the conditions at the panelboard. Locate this identifi cation on the dead front cover or on the cabinet door.
4. Secure back-fed circuit breakers and other overcurrent protection devices with a fastener that prevents the device from being removed from the panelboard without fi rst removing the fastener.This means that when a circuit breaker is installed in a regular slot on the panelboard and that circuit breaker serves as the power source for that panel, that circuit breaker should not be easily removable. This prevents accidental shock and electrical fires should the back-fed device become disconnected. Back-fed circuit breakers are common in some subpanels and where solar photovoltaic systems connect to panelboards.

Wire Sizing and Overcurrent Protection

NM Cable (Romex®) Ampacity and Overcurrent Protection
1. Use Table E3705.-1 to determine the maximum ampacity and overcurrent protection of NM cable. NM cable is often referred to by the trade name Romex®. This table will apply to almost all branch circuit and feeder wires in modern residential electrical systems.
2. Do not apply the temperature and proximity adjustment factors to NM cable if the adjusted value exceeds the value in the Table E3705.-1. Example: Use the 20 amp value in Table E3705.-1 if the temperature or proximity adjustment for NM cable is 25 amps.
3. Apply the temperature and proximity adjustment factors to NM cable is the adjusted value is less than the value in Table E3705.-1. Example: Do not the 20 amp value in Table E3705.-1 if the temperature or proximity adjustment for NM cable is 15 amps. Read the full Topic