Number of Receptacles/Lights on Circuit

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Old 08-20-02, 03:24 PM
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Number of Receptacles/Lights on Circuit

I am sure this has been addressed, but I couldn't find any old posts that discuss this.

When installing a new circuit - lets say a 20A breaker on 12 gage wire - how do you determine how many receptacles and/or lights can be placed on each circuit?

Thanks,

abkent
 
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Old 08-20-02, 07:25 PM
Artcarney
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recpt.

CALCULATE THE NUMBER OF GENERAL LIGHTING RECEPTACLES AS FOLLOWS
100% CAPACITY IN VOLT AMPS [WATTS] OF A 12 Awg. NONMETALLIC SHEATHED CABLE “ROMEX” EQUALS 2,400 VOLT AMPS [WATTS].

20 AMP MULTIPLIED BY 120 VOLTS = 2,400 Va @ 100%. ON A 20 AMP CIRCUIT

IF YOU ARE WIRING YOUR GENERAL LIGHTING TYPE RECEPTACLES WITH 12 Awg., THEN DIVIDE THE TOTAL VOLT AMPS REQUIRED FOR GENERAL LIGHTING BY 2,400 VOLT AMPS [WATTS].

100% CAPACITY IN VOLT AMPS [WATTS] OF A 14 Awg. NONMETALLIC SHEATHED CABLE ”ROMEX” EQUALS 1,800 VOLT AMPS “WATTS”.

15 AMP DIVIDED BY 120 VOLTS = 1,800 Va @ 100%. ON A 15 AMP CIRCUIT

IF YOU ARE WIRING YOUR GENERAL LIGHTING TYPE RECEPTACLES WITH 14 Awg., THEN DIVIDE THE TOTAL VOLT AMPS REQUIRED FOR GENERAL LIGHTING BY 1,800 VOLT AMPS THUS MEETING THE REQUIREMENTS IN TABLE 220.3.A, CALLING FOR 3 VOLT AMPS PER SQUARE FEET TO FIND THE MAXIMUM NUMBER OF RECEPTACLES ALLOWED ON A GENERAL LIGHTING BRANCH CIRCUIT.

Measure the outside dimensions of your dwelling living areas, not including the garage [ but be sure to include the finished part of a basement in your total square foot measurements]. Multiply the length times the width of each living area that you measured, and add the total square feet area of each of these living areas together to discover the total square footage of your living areas. That total gives you the total square feet of living space in your dwelling. Now multiply that answer times 3 volt amps. [ approximate watts ]. This total gives you the volt amps [approximate watts] that you will be required to provide for your general lighting receptacles and luminaire. TABLE 220.3.A

Now divide that total volt amps required to serve the living areas general lighting [including convenience receptacles] in your dwelling by either 2,400 Va. if wired by 12 Awg. Romex, or divide by 1,800 Va. if wired with 14 Awg. Romex. The answer you get from that division gives you the total number of general lighting branch circuits, the National Electrical Code requires you to have, serving your dwelling. 210.11.A and .B and TABLE 220.3.A

Now add all of the general use receptacles [this means all receptacles not including dedicated circuits, and any receptacles in the kitchen, nook, dining room, pantry, or laundry].210.11.C

Now take the total number of general use receptacles, and divide that total by the number of general lighting branch circuits that you figured, as required. This will tell you the maximum number of general-use type receptacles that you may put on each general-lighting branch circuit. 211.B

AN EXPLANATION OF THIS TYPE OF CALCULATION REQUIRED TO FIND THE MAXIMUM NUMBER OF RECEPTACLES ALLOWED ON A CIRCUIT FOR GENERAL USE WOULD BE IF YOU PUT A RECEPTACLE ON EVERY STUD IN THE DWELLING, YOU MAY HAVE AS MANY AS 100 OR MORE RECEPTACLES PER GENERAL LIGHTING BRANCH CIRCUIT YET YOUR LOAD ON THAT CIRCUIT WOULD NOT INCREASE WITH THOSE EXTRA ADDED RECEPTACLES.

“Special Notes” If you meet the 6’/12’ rule 210.52.A.1 as a minimum in a bedroom, you might average around 5 or 6 receptacles per bedroom. Of those 5 or 6 receptacles you probably would only actually use 2 o3 receptacles. The average loads in the bedroom would probably be maybe a television, stereo, alarm clock, table lamps, etc. these are very light loads. The total receptacle load in the average bedroom would not normally be over maybe 4 amps.

Now let’s install a receptacle on every stud in that average bedroom we now might have 50 to 75 receptacles or more. How many receptacles would you use now ? Maybe the same 2 or 3 ?

This is why the NEC allows the calculations mentioned above as the method of calculation to find the receptacle circuitry design.
 
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Old 08-20-02, 07:43 PM
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generally not more than 10 general use on 12 and 8 on 14. I do things for myself so I like to keep the loads light so additions can be done with no worry. If you are doing for yourself wire and breakers are cheap. My place is a little different so it can be customized and I added as I went,, lots of dedicated circuits for specialty things. You usually dont have that luxury in a typical home though. I am just babbling,,, the last post said the right way to calculate it.
 
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Old 08-20-02, 09:31 PM
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Re:

Artcarney is correct, I believe you will find this same information on http://www.homewiringandmore.com/
I stick with about 10, or if there is enough breaker space then I will try to put each room on it's own breaker. or no more than two rooms on a breaker.
 
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Old 08-21-02, 01:55 PM
Canoe875
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here in northwest ohio we have very specific codes as to how many watts we can put on a circuit. We are not allowed to put more than 1500 watts on a 15 amp circuit and 2000 watts on a 20 mamp circuit. Bedroom plugs = 100 watts a piece
ceiling fans = 200 vanity lights 200 hall outlets 150
outside and living room 300 and every ceiling fixture and outlet for each room has an assigned power rating. Thats how we do it here. let me know if i can help you futher
 
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