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I need to wire 2 bedrooms and a living area. Rather than the addition of a separate lighting circuit with wires going everywhere above, I plan to run each room on a separate 20amp circuit (12/2) with shared receptacles and lights.

Starting my home run from outlet to outlet then simply T-ing off an outlet where a switch would be located above, I could run power to the switch, then to the light. Now back at the T junction, power would continue down the line of outlets finishing till the end of the circuit. My wiring would be in parallel, so pig tails on everything, also would be using a deep enough box to house the 3 sets of wires coming into the T junction outlet box(power in, power out, power to switch and pigtails to power outlet). Is there anything wrong or against code with this method of wiring??

I am aware that most people run separate lighting circuit, mostly for the sake of not losing light if a breaker flips, but for me that does not out weigh a simple branch off an outlet for ease of install and less wire to run, less connections, less potential hazards. In my mind it makes sense and is efficient. Am I missing anything? What do you guys think? any info would be much appreciated.

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    With the current NEC requiring a neutral at the switch I don't think there are many electricians that run a separate lighting circuit since it would require 12/3 for the switch loop. – NoSparksPlease Oct 29 '20 at 3:04
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    All it takes is 14/2 and planning, actually. Or two 14 THHN and EMT and planning. If the power goes to the switch first, then you don't need a switch loop - and there's no need for 20A lighting circuits if using modern efficient lights in any reasonable scale house. But suit yourself and have fun stumbling around in the dark. – Ecnerwal Oct 29 '20 at 3:43
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    Interesting. The electricians I've spoken to asking for advice tell me that an independent lighting circuit is preferred. Saying "If you want it to be safe" This is the first I've heard of not running a separate lighting circuit. Thank you for your input NoSparks – Mr. Marron Oct 29 '20 at 3:51
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    @ Ecnerwal Power will be running to the switch first, indeed eliminating the need for a switch loop. I have higher power needs than most, hence the 20amp circuit. Since the outlets will be run on 12/2, the same wire will be used on the whole circuit including lights. And I mean really, how often to you blow a breaker? like once every couple years? I can manage like 1 min of darkness to run out and flip a breaker. – Mr. Marron Oct 29 '20 at 4:05
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    If you "have higher power needs than most" then sharing lighting and outlets is counterproductive. Unless you install antiquated lighting 15A is more than plenty for lighting, and that lighting is not using any power from your 20A outlet circuit, and can run on less expensive 14Ga wire. Having lived with lighting and outlets on the same circuit, I prefer not to repeat that painful experience. – Ecnerwal Oct 29 '20 at 4:17
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Electricians have debated this for a long time with no decisive winner, so it's a safe bet there's no right or wrong answer, both ways have merit. But the layout you propose is fine.

Some decide based on cost considerations. Some like the additional power available per room.

Some think it's bad for the lights to go out when someone trips a breaker with a plug in device, since they may have to navigate in the dark to go reset the breaker.

Some like the idea that you can put the smoke detectors on the lighting circuit and if that circuit trips the breaker for any reason, you'll know because the lights won't work.

I prefer the arrangement you propose, a 20A circuit per room for lights and receptacles, with 15A receptacles. My favorite reason is space heaters, in my opinion that's what settles it.

Very few homes have heating that separates every room on its own thermostat. There are not many families where everyone is comfortable at the same temperature. Therefore, sometimes people use space heaters.

Electricians hate space heaters, and tell homeowners they should not use them, because they mess up their plans to put a lot of space on a single circuit. In my opinion, this is the tail wagging the dog, the homeowner isn't supposed to worry about what the electrician would want in their home. The electrician's design should anticipate the homeowner's demand.

One other suggestion along these lines. Even if you're not going to install a ceiling fan right now, provide for it with your wiring. It's a difficult retrofit but it's only a little extra effort and expense now to set up for a ceiling fan later. Electricians also hate ceiling fans, but some homeowners love them.

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  • If you have lights and receptacles on the same 20 A circuit, will the lights dim when you plug in a vacuum cleaner or when an electric space heater cycles on. – Jim Stewart Oct 29 '20 at 11:48
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    @JimStewart - that effect comes from voltage drop. Whether the loads are on the circuit, or on separate circuits on the same panel, the lights may see some dimming or flicker if something draws a big inrush current on a receptacle. See mikeholt.com/mojonewsarchive/All-HTML/HTML/… – batsplatsterson Oct 29 '20 at 13:16
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    @JimStewart - there's so many different variants out there, many handle a wide range of input voltages, some are constant current output, some are constant voltage output, there are even PoE LED lights ledsupply.com/blog/… – batsplatsterson Oct 29 '20 at 15:43
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    @JimStewart - the most common location for the driver is probably inside the wall or ceiling near the fixture, so you can get at the driver by taking down the fixture – batsplatsterson Oct 29 '20 at 15:47
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    @batsplatsterson I agree, the extra available load on the circuit for items like space heaters, mini fridges, vacuums etc, is a plus. For me the ease of, and more simplistic wiring is key. Good call on the ceiling fan, that will be included in the plan. Appreciate your answer – Mr. Marron Oct 29 '20 at 17:35

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