Subject: Re: How many outlets on a circuit?
From: Redwood Kardon <redwood@codecheck.com>
Date: 03/08/1997
Newsgroups: alt.home.repair,misc.comsumers.house

> On Fri, 01 Aug 1997 , jeffcarp@usa.net (Jeff Carpenter) wrote:
> >Each outlet is rated 180 VA according to the NEC. IF you know the load of what you are going to plug into the outlet, I would use that lload instead of the 180 VA. You can only use the actual load if it is LARGER than 180 VA.

RK responds- The 180VA(NEC 220-13) is for *non-dwelling unit* calculations only. It is not relevant to this situation. The NEC does not limit the number of outlets on a general purpose circuit in anyway. Local amendments might have limitations, but you have to check with the authority having jurisdiction for those.

Jeff is right in one respect though. From a common sense point of view you should determine the actual loading of outlets to determine the number of outlets on a circuit. Being completely conservative, you can figure all the loads as continuous loads(3.hrs) and multiply the ampacity of the circuit by 80% (inversely, 125% of the continuous load) i.e. a 15 amp circuit can run 12 amps continuous and a 20 amp circuit 16 amps of continuous load. Like I said these values are somewhat conservative but will provide plenty of cush.

> >So basically, you have a total of 200 + 33 + (4*180) = 953 VA.

If you were calculating a commercial load this would be correct. The 180 VA is for a single or multiple receptacle on a single strap(mounting yoke).

Here is a quote from the NEC handbook (published by the NFPA) on this oft confused non-requirement.

Section 220-4 Branch Circuits Required.
No restriction is placed on the number of outlets connected to a general lighting or small-appliance branch-circuit. The number of general receptacle outlets in a room is determined by Section 210-52(a). ...
Consideration must be given to balancing the loads when terminating circuits in panelboards.

220-3. Computation of Branch Circuits. [This section describes how to size the circuit. rk]

Branch-circuit loads shall be computed as shown in (a) through (d) below.

(a) Continuous [A load where the maximum current is expected to continue for three hours or more.] and Noncontinuous Loads. The branch-circuit rating shall not be less than the noncontinuous load plus 125 percent of the continuous load. The minimum branch-circuit conductor size, without the application of any adjustment or correction factors, shall have an allowable ampacity equal to or greater than the noncontinuous load plus 125 percent of the continuous load.
...

(b) Lighting Load for Listed Occupancies. A unit load of not less than that specified in Table 220-3(b) [3 watts per sq. ft. for dwelling units **] for occupancies listed therein shall constitute the minimum lighting load for each square foot (0.093 sq m) of floor area. The floor area for each floor shall be computed from the outside dimensions of the building, dwelling unit, or other area involved. For dwelling units, the computed floor area shall not include open porches, garages, or unused or unfinished spaces not adaptable for future use. ...

[This section describes how many circuits, not outlets, are required. i.e. 2500 square foot of habitable space would requre 5 general purpose circuits. 2500 x 3 watts per sq.ft. = 7500 watts 7500/1440 (15amperes x 120 volts x .8 = 1440) = 5.2 or 6- 15 ampere circuits. OR 7500/1920 (20 amperes x 120 volts x .8 = 1920) = 3.9 or 4- 20 ampere circuits.

A common rule of thumb is to figure a 15 ampere ciruit as being able to handle1500 watts (the .8 multiplier is very conservative). Thus each 500 square feet of habitable space requires at least one 15 ampere circuit. The number of outlets should be determined by the distribution of loads. rk]

(c) Other Loads -- All Occupancies. In all occupancies, the minimum load for each outlet for general-use receptacles and outlets not used for general illumination [my empahsis.rk]hsall be not less than the following, the loads shown being based on nominal branch-circuit voltages.
(1)Outlet for specific appliance...

(2) Outlet for motor load...

(3) Recessed lighting...

(4) Outlet for heavy-duty lampholder ......... 600 volt-amperes.

(5) Track lighting (see Section 410-102). ...

(6) Sign and outline lighting...

(7) Other outlets* ......... 180 volt-amperes per outlet. [It is a common mistake to see this and not note the asterisk.]
...
*This provision shall not be applicable to receptacle outlets connected to the circuits specified in Sections 220-4(b) and (c). [This excludes small appliance and laundry circuits from the 180 volt ampere calculation, essentially restricting the use of 180 volt-ampere per outlet to commercial applications.rk]

220-4. Branch Circuits Required.

Branch circuits for lighting and for appliances, including motor-operated appliances, shall be provided to supply the loads computed in accordance with Section 220-3. In addition, branch circuits shall be provided for specific loads not covered by Section 220-3 where required elsewhere in this Code; for small appliance loads as specified in (b) below; and for laundry loads as specified in (c) below.

(a) Number of Branch Circuits. The minimum number of branch circuits shall be determined from the total computed load and the size or rating of the circuits used. In all installations, the number of circuits shall be sufficient to supply the load served. In no case shall the load on any circuit exceed the maximum specified by Section 210-22.

(b) Small Appliance Branch Circuits -- Dwelling Unit. In addition to the number of branch circuits determined in accordance with (a) above, two or more 20-ampere small appliance branch circuits shall be provided for all receptacle outlets specified by Section 210-52 for the small appliance loads.

(c) Laundry Branch Circuits -- Dwelling Unit. In addition to the number of branch circuits determined in accordance with (a) and (b) above, at least one additional 20-ampere branch circuit shall be provided to supply the laundry receptacle outlet(s) required by Section 210-52(f). This circuit shall have no other outlets.

(d) Load Evenly Proportioned Among Branch Circuits. Where the load is computed on a volt-amperes-per-square foot (0.093-sq m) basis, the wiring system up to and including the branch-circuit panelboard(s) shall be provided to serve not less than the calculated load. This load shall be evenly proportioned among multioutlet branch circuits within the panelboard(s). Branch-circuit overcurrent devices and circuits need only be installed to serve the connected load.

**Table 220-3(b) Note- [Table specifies watts per sq.ft.]
All general-use receptacle outlets of 20-ampere or less rating in one-family, two-family, and multifamily dwellings and in guest rooms of hotels and motels except those connected to the receptacle circuits specified in Sections 220-4(b) and (c)] shall be considered as outlets for general illumination, and no additional load calculations shall be required for such outlets.

210-52. Dwelling Unit Receptacle Outlets [spacing].

(a) General Provisions. In every kitchen, family room, dining room, living room, parlor, library, den, sun room, bedroom, recreation room, or similar room or area of dwelling units, receptacle outlets shall be installed so that no point along the floor line in any wall space is more than 6 ft (1.83 m), measured horizontally, from an outlet in that space, including any wall space 2 ft (610 mm) or more in width and the wall space occupied by fixed panels in exterior walls, but excluding sliding panels in exterior walls. The wall space afforded by fixed room dividers, such as freestanding bar-type counters or railings, shall be included in the 6-ft (1.83-m) measurement.

As used in this section, a "wall space" shall be considered a wall unbroken along the floor line by doorways, fireplaces, and similar openings. Each wall space 2 ft or more (610 mm or more) wide shall be treated individually and separately from other wall spaces within the room. A wall space shall be permitted to include two or more walls of a room (around corners) where unbroken at the floor line.

Receptacle outlets shall, insofar as practicable, be spaced equal distances apart. Receptacle outlets in floors shall not be counted as part of the required number of receptacle outlets unless located within 18 in. (457 mm) of the wall.

The receptacle outlets required by this section shall be in addition to any receptacle that is part of any lighting fixture or appliance, located within cabinets or cupboards, or located over 5 1/2 ft (1.68 m) above the floor.

Exception: Permanently installed electric baseboard heaters equipped with factory-installed receptacle outlets or outlets provided as a separate assembly by the manufacturer shall be permitted as the required outlet or outlets for the wall space utilized by such permanently installed heaters. Such receptacle outlets shall not be connected to the heater circuits.

(FPN): Listed baseboard heaters include instructions that may not permit their installation below receptacle outlets.

(b) Small Appliances.

(1) In the kitchen, pantry, breakfast room, dining room, or similar area of a dwelling unit, the two or more 20-ampere small appliance branch circuits required by Section 220-4(b) shall serve all receptacle outlets covered by Sections 210-52(a) and (c) and receptacle outlets for refrigeration equipment.

(2) The two or more small appliance branch circuits specified in (b)(1) above shall have no other outlets.

Exception No. 1: A receptacle installed solely for the electrical supply to and support of an electric clock in any of the rooms specified above.

Exception No. 2: Receptacles installed to provide power for supplemental equipment and lighting on gas-fired ranges, ovens, or counter-mounted cooking units

(3) Receptacles installed in the kitchen to serve countertop surfaces shall be supplied by not less than two small appliance branch circuits, either or both of which shall also be permitted to supply receptacle outlets in the kitchen and other rooms specified in Section 210-52(b)(1). Additional small appliance branch circuits shall be permitted to supply receptacle outlets in the kitchen and other rooms specified in Section 210-52(b)(1).

(c) Countertops. In kitchens and dining rooms of dwelling units, receptacle outlets for counter spaces shall be installed in accordance with (1) through (5) below.

(1) Wall counter space. A receptacle outlet shall be installed at each wall counter space 12 in. (305 mm) or wider. Receptacle outlets shall be installed so that no point along the wall line is more than 24 in. (610 mm), measured horizontally from a receptacle outlet in that space.

(2) Island counter spaces. At least one receptacle outlet shall be installed at each island counter space with a long dimension of 24 in. (610 mm) or greater and a short dimension of 12 in. (305 mm) or greater.

(3) Peninsular counter space. At least one receptacle outlet shall be installed at each peninsular counter space with a long dimension of 24 in. (610 mm) or greater and a short dimension of 12 in. (305 mm) or greater. A peninsular countertop is measured from the connecting edge.

(4) Separate spaces. Countertop spaces separated by range tops, refrigerators, or sinks shall be considered as separate countertop spaces in applying the requirements of (1), (2), and (3) above.

(5) Receptacle outlet location. Receptacle outlets shall be located not more than 18 in. (458 mm) above the countertop. Receptacle outlets shall not be installed in a face-up position in the work surfaces or countertops. Receptacle outlets rendered not readily accessible by appliances fastened in place or appliances occupying dedicated space shall not be considered as these required outlets.

Exception: Where acceptable to the authority having jurisdiction and to meet the special conditions as specified in a or b below, receptacle outlets shall be permitted to be mounted not more than 12 in. (305 mm) below the countertop. Receptacles mounted below the countertop in accordance with this exception shall not be located where the countertop extends more than 6 in. (153 mm) beyond its support base.

a. Construction for the physically impaired.

b. Where island or peninsular counter space construction precludes practical mounting above the countertop.

(d) Bathrooms. In dwelling units, at least one wall receptacle outlet shall be installed in bathrooms adjacent to each basin location. Bathroom receptacle outlets shall be supplied by at least one 20-ampere branch circuit. Such circuits shall have no other outlets. See Section 210-8(a)(1)[GFCI reqs.].

Receptacle outlets shall not be installed in a face-up position in the work surfaces or countertops in a bathroom basin location.

(e) Outdoor Outlets. For a one-family dwelling and each unit of a two-family dwelling that is at grade level, at least one receptacle outlet accessible at grade level and not more than 6 ft, 6 in. (1.98 m) above grade shall be installed at the front and back of the dwelling. See Section 210-8(a)(3)[GFCI reqs.].

(f) Laundry Areas. In dwelling units, at least one receptacle outlet shall be installed for the laundry....

(g) Basements and Garages. For a one-family dwelling, at least one receptacle outlet, in addition to any provided for laundry equipment, shall be installed in each basement and in each attached garage, and in each detached garage with electric power. See Sections 210-8(a)(2) and (a)(4)[GFCI reqs.].

(h) Hallways. In dwelling units, hallways of 10 ft (3.05 m) or more in length shall have at least one receptacle outlet.

As used in this subsection, the hall length shall be considered the length along the centerline of the hall without passing through a doorway.

210-22. Maximum Loads.

The total load shall not exceed the rating of the branch circuit, and it shall not exceed the maximum loads specified in Sections 210-22(a) through (c) under the conditions specified therein.

(a) Motor loads...

(b) Inductive Lighting Loads. For circuits supplying lighting units having ballasts, transformers, or autotransformers, the computed load shall be based on the total ampere ratings of such units and not on the total watts of the lamps.

(c) Other Loads. The rating of the branch-circuit overcurrent device serving continuous loads, such as store lighting and similar loads, shall be not less than the noncontinuous load plus 125 percent of the continuous load. The minimum branch-circuit conductor size, without the application of any adjustment or correction factors, shall have an allowable ampacity equal to or greater than the noncontinuous load plus 125 percent of the continuous load.

Exception: Circuits supplied by an assembly, together with its overcurrent devices, that is listed for continuous operation at 100 percent of its rating.

Miller, Bruce E. wrote:
>
> First of all, thanks for the information! Second, a question: I assume an outlet is defined as a single outlet? Does that mean that a duplex outlet is twice that? Thus, 4 duplex outlets will be 8*180?
> Thanks,
> bruno @ clark . net
>