Number Of Lighting Circuits Required

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jetlag

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Eatonton, Georgia
Is this a valid method to determine the number of 15 amp general purpose receptacles and lighting circuits required for a dwelling ? All you do is multiply the number of square ft in the house by 3 VA per sq ft , and then divide the total by 1800 Va and that gives you the number 14 gauge 15 amp circuits . I know people use that method for figuring the service demand be I never thought it was enough for each branch circuit . For example : if a dwelling had 4 small bedrooms , 150 sq ft each that would be 600 sq ft . if you multiply 600 by 3va = 1800 Va . That means you could put all the gen purpose receptacles an lights in all 4 bed rooms on one 15 amp circuit . That just does not seem right to me . ' I'm not talking about the other rooms right now or where the 20 amp circuits are required , just the 4 bedrooms .
 
Just what do you think the actual load will be in those bedrooms? Limited to sleeping use, well less than 15. Throw in a treadmill?

I always went by # of openings but that isn't a set in stone method either. Some areas use 150 watts per receptacle. I suspect you could use one circuit for all the LED lights in the house.
 
Some small dwellings can easily have all the lighting on a single circuit particularly with LED usage. But I will always use more than one for convenience, and to prevent a trip for whatever reason leaving HO in total darkness. Also even though its allowed I don't put the lights on the general purpose receptacle circuits, for same reason that if something trips the circuit it would leave the person in the dark.
 
With the advent of central heating and air, electric blankets ( do they still even make those?) and electric heaters in bedrooms are not so common anymore. (Except in older houses) Even though it’s overkill, I usually put one circuit in each bedroom. Also a separate circuit in each bathroom. (With tract housing the roper’s tend to loop all bathrooms together).
 
jetlag said:
Is this a valid method to determine the number of 15 amp general purpose receptacles and lighting circuits required for a dwelling ? All you do is multiply the number of square ft in the house by 3 VA per sq ft , and then divide the total by 1800 Va and that gives you the number 14 gauge 15 amp circuits . I know people use that method for figuring the service demand be I never thought it was enough for each branch circuit . For example : if a dwelling had 4 small bedrooms , 150 sq ft each that would be 600 sq ft . if you multiply 600 by 3va = 1800 Va . That means you could put all the gen purpose receptacles an lights in all 4 bed rooms on one 15 amp circuit . That just does not seem right to me . ' I'm not talking about the other rooms right now or where the 20 amp circuits are required , just the 4 bedrooms .
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Lets not forget the purpose of the Code. Its written from a protection and a minimum now standpoint. Can always go above and beyond that for an extra cost to the customer. :)
 
I'll usually do two bedrooms on a circuit, Master usually on its own, but it does depend on the situation, and my mood at the time 😉. What makes it tricky around here is the potential for window air conditioners. We are in Central New York state so very few homes have central air, but does get hot enough sometimes where people are very likely to throw in window AC's, so I feel obligated to account for that possibility.
 
ptonsparky said:
Just what do you think the actual load will be in those bedrooms? Limited to sleeping use, well less than 15. Throw in a treadmill?

I always went by # of openings but that isn't a set in stone method either. Some areas use 150 watts per receptacle. I suspect you could use one circuit for all the LED lights in the house.
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I like the per opening better , if there were 6 in each bedroom that would be 24 openings for the 4 bedrooms . at 150 watts would be 3600 watts and that's exactly two 15 amp circuits . and that would be two bedrooms on each circuit . I like to be able to use a vacuum cleaner without the breaker tripping . That's usually 1100 watts , but still should be ok . Thanks for reply
 
electrofelon said:
I'll usually do two bedrooms on a circuit, Master usually on its own, but it does depend on the situation, and my mood at the time 😉. What makes it tricky around here is the potential for window air conditioners. We are in Central New York state so very few homes have central air, but does get hot enough sometimes where people are very likely to throw in window AC's, so I feel obligated to account for that possibility.
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It's in the code somewhere that a fixed in place appliance can pull no more than 40 percent of the circuit ratting so the room air conditioner should be limited to 6 amps . so I am going like you with 2 bedrooms per circuit on this house Thanks for reply
 
If the goal is to use only 15a circuits, I would use two for receptacles and a third for lights and fans.

I prefer 20a circuits for receptacles, and a single 20a may be enough as only one vacuum is used.
 
xformer said:
Get ready for 10 a circuits. :)
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Haven't seen any 10A breakers around here, but maybe not going to for a while, still on '17 code. But my understanding is that the 10A was only going to be on the lighting circuits and still need to be installing a 14G wire as smallest allowed. So not sure of the advantage of the 10A circuit.
 
Many great answers above, typically suggested was 180VA per receptacle/light ( 10 locations ) will pass a city residential inspection ( in Calif ). commercial usually required 280VA ( 6 locations ) although based on all the possible scenarios like 1500w floor heaters or as mentioned earlier a treadmill the above allowances would be insufficient. Just keep in mind the electrical budget, typical purpose and most importantly what the city code will approve, the city code can very well supersede a basic NEC standard. I agree with an above statement that its best to give the receptacles a strong 20A supply, let the lighting work off the 15's
 
Fred B said:
Haven't seen any 10A breakers around here, but maybe not going to for a while, still on '17 code. But my understanding is that the 10A was only going to be on the lighting circuits and still need to be installing a 14G wire as smallest allowed. So not sure of the advantage of the 10A circuit.
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The goal of the 10 amp circuits was to permit the use of 14 AWG copper clad aluminum, but that part did not make it through the 2023 code process. I expect it will for the 2026.
 
Fred B said:
Haven't seen any 10A breakers around here, but maybe not going to for a while, still on '17 code. But my understanding is that the 10A was only going to be on the lighting circuits and still need to be installing a 14G wire as smallest allowed. So not sure of the advantage of the 10A circuit.
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It’s copper clad Aluminum, so less expensive than copper.
It will be confusing for HI when they see a 10 amp breaker.
 
tom baker said:
It’s copper clad Aluminum, so less expensive than copper.
It will be confusing for HI when they see a 10 amp breaker.
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It is my understanding the CCA is about 20% cheaper than copper for the same current. That is you use 12 AWG CCA where you would use 14 AWG copper.
I think a bigger issue will be the identification of the wire type...If you can't see the end, you don't know if it is copper or CCA.
 
hillbilly1 said:
#14 copper breaks easy enough, I would hate to think what #14 aluminum would do. Apparently history is doomed to repeat itself.
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I have found a lot of defective (old style) residential aluminum wiring in the past. Caused by loose/improper connection. Since then, always thought it wasn't worth the savings compared to copper, and when it goes bad, it really goes bad !
 
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