ec&m branch circuits – part 1

8/20/2014 Branch Circuits Part 1

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Branch Circuits Part 1

Electrical Construction and Maintenance

Mike Holt, NEC Consultant

Mon, 2011-01-24 16:48

The ins and outs of branch circuit installations

The distinction between a branch circuit and a feeder can be a source of confusion for many Code users.

The first step in eliminating this confusion is to understand that the NEC defines a branch circuit as the

conductors between the branch circuit final overcurrent device protecting the circuit and the outlets

(such as receptacles or lights) [Art. 100], as shown in Fig. 1. By contrast, a feeder circuit runs from the

service equipment, the source of a separately derived system, or other power supply to (rather than from)

the final branch circuit overcurrent device.

Fig. 1. The conductors between the final overcurrent device and the outlet(s) are defined as branch

circuit conductors.

The size of the circuit breaker installed on a branch circuit, not the conductor size, determines the rating of

the circuit. Therefore, if the conductor size is increased to accommodate for voltage drop or for ampacity

adjustment or correction purposes, the rating of the circuit remains the same as the circuit breaker size

supplying it [210.3].

Youll find branch circuit requirements for conductor sizing, overcurrent protection, identification, GFCI

protection, receptacles, and lighting outlets in Art. 210. Other Articles may apply to your installation;

youll find those listed in 210.2.

Multiwire branch circuits

A multiwire branch circuit basically consists of two or more ungrounded conductors that share a neutral.

All conductors of a multiwire branch circuit must originate from the same panelboard [210.4(A)].



For personnel safety, each multiwire branch circuit must have a means to simultaneously disconnect all

ungrounded conductors at its origin [210.4(B)]. If that origin is two or more breakers, you can provide this

disconnect by using single-pole circuit breakers with handle ties identified for the purpose [240.15(B)(1)].

Multiwire branch circuits can supply only line-to-neutral loads [210.4(C)], except that a multiwire branch

circuit can also supply:

An individual piece of line-to-line utilization equipment, such as a range or dryer [210.4(C) Ex 1].

Both line-to-line and line-to-neutral loads if the circuit is protected by a device such as a multipole

circuit breaker with a common internal trip that opens all ungrounded conductors of the multiwire

branch circuit simultaneously under a fault condition [210.4(C) Ex 2].

In multiwire branch circuits, the continuity of the neutral conductor must not be interrupted by the

removal of a wiring device. In these applications, the neutral conductors must be spliced together at every

device providing a pigtail to terminate to the wiring device [300.13(B)]. The opening of the ungrounded

conductors, or the neutral conductor of a 2-wire circuit during the replacement of a device, doesnt cause a

safety hazard, so pigtailing these conductors isnt required [110.14(B)]. Caution: If the continuity of the

neutral conductor of a multiwire circuit is interrupted (opened), the resultant over- or undervoltage can

cause a fire and/or destruction of electrical equipment.

The ungrounded and neutral conductors of a multiwire branch circuit must be grouped together using

cable ties or similar means at the point of origination [210.4(D)]. These conductors are not required to be

grouped if they are contained in a single raceway or cable unique to that circuit, making the grouping

obvious.

If the ungrounded conductors of a multiwire circuit dont terminate to different phases or lines, the

currents on the neutral conductor will add instead of canceling each other out, possibly overloading the

neutral conductor.

Identification

Equipment grounding conductors are allowed to be bare, covered, or insulated. Insulated equipment

grounding conductors size 6 AWG and smaller must have a continuous outer finish either green or green

with one or more yellow stripe(s) [250.119]. If installing equipment grounding conductors

4 AWG and larger, you can permanently reidentify the insulation with green markings or tape, or strip the

insulation off of the conductor. This reidentification must be done at every point where the conductor is

accessible [250.119(A)].

Identify the neutral (grounded) conductor per 200.6. If 6 AWG or smaller, it must be white, gray, or

some color other than green with white stripes along its entire length. For 4 AWG and larger, the same

means of identification can be used, or it is allowed to use white or gray tape at terminations.

If you have more than one voltage system, then for each ungrounded conductor [210.5(C)]:

Identify it by phase and system at all termination, connection, and splice points.

Identification can be by color coding, marking tape, tagging, or other means approved by the AHJ.

Document the method of identification in a manner thats readily available or permanently posted at

each branch circuit panelboard.

Voltage limitations



In dwelling units, the voltage between conductors must not exceed 120V, nominal, when they supply the

terminals of [210.6(A)] luminaires or cord- and plug-connected loads less than hp or less than or equal

to 1,440VA [21.6].

Multiple branch circuits

If two or more branch circuits supply devices (or equipment) on the same yoke, a means must be provided

at the circuits point of origin to disconnect simultaneously all ungrounded conductors that supply those

devices [210.7].

GFCI for dwelling units

Install a GFCI at a readily accessible location for all 15A and 20A, 125V receptacles located in the following

locations [210.8(A)]:

Bathrooms.

Garages and accessory buildings.

Outdoors.

Crawl spaces.

Unfinished basements.

Serving kitchen countertops.

Within 6 ft of the outside edge of sinks, in addition to the requirements for kitchen sinks.

Boathouses.

Also:

Each dwelling unit of a multifamily dwelling that has its own grade level entrance must have at least

one accessible GFCI-protected receptacle at 6 ft or less above grade [210.52(E)(2)].

Balconies, decks, and porches attached to the dwelling unit and accessible from inside the dwelling

must have at least one GFCI-protected receptacle outlet accessible from the balcony, deck, or porch

[210.52(E)(3)].

However, you dont need GFCI protection for a receptacle supplied by a branch circuit dedicated to fixed

electric snow-melting, deicing, pipeline heating, or vessel heating equipment, if:

The receptacle isnt readily accessible, and

The equipment or receptacle has ground-fault protection of equipment (GFPE) [426.28 and

427.22].

GFCI for non-dwelling units

Install GFCI at a readily accessible location for all 15A and 20A, 125V receptacles in any of the following

commercial/industrial locations [210.8(B)]:

Bathrooms.

Kitchens (not required for hard-wired equipment).

Rooftops (A 15A or 20A, 125V receptacle must be installed within 25 ft of heating, air-conditioning,

and refrigeration equipment [210.63]).

Outdoors.

Sinks (except in laboratories where removal of power would introduce a greater hazard or in patient

bed locations of general care or critical care areas of health care facilities).



Indoor wet locations.

Locker rooms with associated showering facilities.

Garages (where electrical diagnostic equipment, electrical hand tools, or portable lighting equipment

are to be used).

Boat hoists.

You dont need GFCI protection for a receptacle supplied by a branch circuit dedicated to fixed electric

snow-melting, deicing, pipeline heating, or vessel heating equipment, if:

The receptacle isnt readily accessible, and

The equipment or receptacle has ground-fault protection of equipment (GFPE) [426.28 and

427.22].

Note: The list of GFCI requirements in 210.8 is not all-inclusive. For example, there are also GFCI

requirements for cord- and plug-connected vending machines and electric drinking fountains in Art. 422

[422.51 and 422.52].

Number of circuits

Theres no maximum number of receptacles on a dwelling unit circuit. But how do you determine the

minimum number of circuits for general lighting and general-use receptacles? Divide the total calculated

load in amperes by the ampere rating of the circuits used [210.11]. See Example D1(a) in Annex D. If you

calculate the total load based on VA/square foot, ensure the individual loads are evenly proportioned

among multioutlet branch circuits within the panelboard.

Required circuits

Its not just the total number of outlets that matters. The NEC also requires certain types of circuits in

specific places in addition to the minimum requirements based on the VA/square foot calculation.

A dwelling unit kitchen, dining room, breakfast room, pantry, or similar area must have at least two 20A,

120V small-appliance receptacle branch circuits [for the 15A or 20A receptacle outlets required in these

rooms by 210.52(B)]. These circuits cant supply other outlets [210.52(B)(2)], including those for lighting.

You can use one 3-wire multiwire circuit or two separate 120V circuits [210.4(A)]. At least two small-

appliance circuits must supply the receptacles above the countertops [210.52(B)(3)].

Provide one 20A, 120V branch circuit for the receptacle outlets required by 210.52(F) for the laundry

room. The 20A laundry room receptacle circuit can supply more than one receptacle in the laundry room.

This receptacle cant supply other outlets, such as the laundry room lighting or receptacles in other rooms

(Fig. 2).



Fig. 2. A 20A laundry room receptacle circuit can supply more than one receptacle in the laundry room,

but there are restrictions, as outlined in 210.52(F).

GFCI protection isnt required for 15A and 20A, 125V receptacles in a laundry room, unless theyre within

6 ft of a sink [210.8(A)(7)].

Provide one 20A, 120V branch circuit for the receptacle outlets required by 210.52(D) for a dwelling unit

bathroom or multiple bathrooms. This circuit cant supply other outlets, such as receptacles in rooms

other than bathrooms or lighting outlets [210.11(C)(3)], as shown in Fig. 3.

Fig. 3. A minimum of one 20A circuit is required to supply the required bathroom receptacles. Other

outlets aren't permitted on the bathroom receptacle circuit.

An alternate method allows this circuit to supply all of the outlets in a single bathroom, including lighting

and fans, if no single load fastened in place is rated more than 10A [210.11(C)(3) Ex and 210.23(A)], as

shown in Fig. 4.



Fig. 4. A single 20A, 120V circuit can supply all of the outlets in a single bathroom, as long as no single

load exceeds 10A.

This gives you a good start on understanding branch circuit requirements. In our next issue, well look at

some additional branch circuit requirements, starting with arc fault circuit interrupters (AFCIs).

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ec&m branch circuits – part 1

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