Note: This article is based on the 2026 NEC^®.

Multiwire Branch Circuits
In accordance with Article 100 a “multiwire branch circuit” is defined as a branch circuit consisting of two or more phase conductors with a neutral conductor having a voltage between the phase conductors and equal voltage from each phase conductor to the neutral conductor.

A multiwire branch circuit can be considered as multiple circuits [210.4(A)]. All conductors of a multiwire branch circuit must originate from the same equipment containing the overcurrent protective devices. The neutral conductor of a multiwire branch circuit is not permitted to be interrupted by the removal of a wiring device [210.4(A) Note 2].

Each multiwire branch circuit must have a means to simultaneously disconnect all phase conductors at the point where the circuit originates [210.4(B)]. Figure 01

This rule is intended to prevent people from working on energized circuits they thought were disconnected. Additionally, failure to terminate the phase conductors to separate phases within the panelboard can cause the neutral conductor to become overloaded.

Multiwire branch circuits must supply only line-to-neutral loads [210.4(C)], but there are two exceptions.

The phase and neutral conductors of a multiwire branch circuit must be grouped or identified together by cable ties, wire markers, or similar means within each enclosure per 200.6(B) [210.4(D)]. Grouping is not required if multiwire branch-circuit conductors pass through a box without splices or terminations [200.6(B) Ex 2].

Conductor Identification
The branch-circuit neutral conductor must be identified per 200.7 [210.5(A)] and the branch-circuit equipment grounding conductor must be identified per 250.119 [210.5(B)].

Identify branch-circuit phase conductors as follows [210.5(C)]:

One Nominal Voltage System. Where the premises wiring system has branch circuits supplied from one nominal voltage system, the branch-circuit phase conductors must be identified per 310.6(A)(3).

More Than One Nominal Voltage System. Where wiring is supplied from more than one nominal voltage system, the branch-circuit phase conductors must be identified by phase and nominal voltage system at termination, connection, and splice points per 210.5(C)(2)(a) and (b).

Means. Identification of the branch-circuit phase conductors can be by color coding, marking tape, tagging, or other means approved by the authority having jurisdiction.

Posting. Branch-circuit phase conductor identification must be readily available or posted at the enclosed panelboard. The identification can’t be handwritten and must withstand the environment involved. But where a different voltage system is added to an existing installation, branch-circuit identification is required only for the new one.

Branch Circuits Required
At least two 20A, 120V small appliance branch circuits are required to supply receptacle outlets in a dwelling unit kitchen, dining room, breakfast room, pantry, or similar area as required by 210.52(B). This circuit cannot supply lighting outlets or any other receptacle outlets [210.11(C)(1)].

One 20A, 120V laundry branch circuit is required to supply the receptacle outlets for a dwelling unit laundry area (per 210.52(F)). This circuit cannot supply lighting outlets or any other receptacle outlets [210.11(C)(2)].

One 20A, 120V bathroom branch circuit is required to supply the dwelling unit bathroom sink receptacle outlets required by 210.52(D). This circuit cannot supply lighting outlets or any other receptacle outlets [210.11(C)(3)].

In dwelling unit garages with electric power, one 20A, 120V branch circuit is required to supply receptacle outlets, including receptacle outlets required by 210.52(G)(1). This circuit is permitted to supply other garage receptacle outlets, but not outlets in other areas of the dwelling unit [210.11(C)(4)].

Branch Circuit Conductor Sizing
Branch circuit conductors must have an ampacity per 210.19(A) through (D).

(A) General. Branch-circuit conductors must have an ampacity no less than the calculated load and must be sized to the larger of either 210.19(A)(1) or (2).

Note: We do not cover 210.19(A)(2) in this Article, but conductor ampacity correction and adjustment will be covered in a future Article.

(1) Continuous and noncontinuous loads. Branch circuit conductors must have an ampacity no less than 125 percent of the continuous loads, plus 100 percent of the noncontinuous loads.

Question: What size conductor is required for a 9,600W, 240V fixed electric space heater with a 3.4A, 240V blower motor where the equipment terminations are rated 75°C? Note: A fixed electric space heater is considered a continuous load in accordance with 424.5. 
(a) 8 AWG (b) 6 AWG (c) 4 AWG (d) 3 AWG
Figure 02
Solution:
Step 1: Determine the total load.
I = Watts/Volts
I = 9,600W/240V
I = 40A
Circuit Current = 40A (heat) + 3.4A (blower)
Circuit Current = 43.4A
Step 2: Size the conductors at 125 percent of the total current load [210.19(A)(1) and 424.5(B)].
Conductor = 43.4A × 125%
Conductor = 54.25A
Conductor = 6 AWG rated 65A at 75°C [Table 310.16 and 110.14(C)(1)(a)(3)].
Answer: (b) 6 AWG

Question: What size circuit breaker is required for a 9,600W, 240V fixed electric space heater with a 3.4A, 240V blower motor? Note: A fixed electric space heater is considered a continuous load in accordance with 424.5.
(a) 40A (b) 45A (c) 50A (d) 60A
Figure 03
Solution:
Step 1: Determine the total load.
I = Watts/Volts
I = 9,600W/240V
I = 40A
Circuit Current = 40A (heat) + 3.4A (blower)
Circuit Current = 43.4A
Step 2: Size the OCPD at 125 percent of the continuous load [424.5]
Protection Rating = 43.4A × 125%
Protection Rating = 54.25A
60A circuit breaker [Table 240.6(A)]
Answer: (d) 60A

Individual Branch Circuits
In accordance with Article 100 a “individual branch circuit” is defined as a branch circuit that supplies only one utilization equipment. An individual branch circuit must have an ampere rating sufficient for the load per manufacturer’s instructions [210.22].

Question: What size individual branch circuit is required for a hood/microwave rated 14.5A?
(a) 10A (b) 15A (c) 20A (d) 25A
Solution:
Answer: (b) 15A
Note: A single receptacle installed on an individual branch circuit must have an ampere rating not less than 100% of the branch circuit [210.21(B)(1)].

Branch Circuit with Multiple Outlets
A 10A branch circuits can supply lighting outlets or dwelling unit exhaust fans on bathroom and laundry room lighting circuits. They cannot supply branch circuit receptacles [210.23(A)].

A 15A or 20A branch circuit can supply lighting, equipment, or both [210.23(B)]. The rating of:

• Cord-and-plug-connected equipment not fastened in place with other outlets can’t exceed 80% of the branch-circuit rating.
• Utilization equipment fastened in place (other than luminaires) can’t exceed 50% of the branch-circuit rating, where lighting units and/or cord-and-plug-connected equipment are also supplied.

Branch Circuit Overcurrent Protection and Conductor Sizing Summary
Sizing the correct branch circuit conductor is important because elevated temperatures on conductors can lead to conductor insulation breakdown and damaged equipment. Sizing the correct overcurrent protection will protect the circuit from overheating.

Both sizing branch circuit conductors and overcurrent protective devices have many variables, but it’s not that hard when you take it step by step. Ask yourself is my branch circuit supplying a continues load? If so, you know that both the branch circuit conductors and overcurrent protective device must be sized at 125 percent.