Another clarification

Old 10-17-01, 04:29 PM
Visiting Guest
Posts: n/a
When calculating load per circuit from duplex outlets, is the assumption 180 volt-amps per plug, equaling 360 volt-amps per duplex outlet. I understand that a dwelling only requires the amps per square footage calc, but wanted to be more rigorous. Using 360 volt-amps per duplex outlet would specify 10 circuits just for outlets (not including special use circuits, and lighting). My house is only 1400 square ft and the amps per square footage calc recommends 3 circuits for outlets and lighting. Am I over the deep end here?
Old 10-17-01, 04:53 PM
Visiting Guest
Posts: n/a
If you wired 13 duplex receptacles on a 20 amp branch circuit or 10 duplex receptacles on a 15 amp branch circuit you would be wiring approximately equal to commercial wiring of multioutlet receptacle circuits. In answer to your question yes a duplex receptacle may be counted at 180 va per duplex receptacle the same as a single outlet.

As for calculating your general lighting your branch circuits should be designed by adding up the total wattage of all lights on the lighting circuit. Considering dwellings you may calculate using 100% of the amp rating of the breaker serving that branch circuit conductor as long as the breaker is properly sized. Commonly people reduce their loading designs by 20% or only loading a lighting circuit to 16 amps on a 20 amp branch circuit.

See the copies of hte NEC 99 version below pertaining to your question.

(9) Receptacle Outlets. Except as covered in (10), receptacle outlets shall be computed at not less than 180 volt-amperes for each single or for each multiple receptacle on one strap. A single piece of equipment consisting of a multiple receptacle comprised of four or more receptacles shall be computed at not less than 90 volt-amperes per receptacle.
This provision shall not be applicable to the receptacle outlets specified in Sections 210-11(c)(1) and (2).
(10) Dwelling Occupancies. In one-family, two-family, and multifamily dwellings and in guest rooms of hotels and motels, the outlets specified in (a), (b), and (c) are included in the general lighting load calculations of Section 220-3(a). No additional load calculations shall be required for such outlets.
a. All general-use receptacle outlets of 20-ampere rating or less, including receptacles connected to the circuits in Section 210-11(c)(3)
b. The receptacle outlets specified in Sections 210-52(e) and (g)
c. The lighting outlets specified in Sections 210-70(a) and (b)
(11) Other Outlets. Other outlets not covered in (1) through (10) shall be computed based on 180 volt-amperes per outlet.

Good Luck


Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: