# 14-3 or 12-3 for smoke detectors?



## Gigs (Oct 26, 2008)

red86yota said:


> Does this mean I need to use the same guage wire for the smokes if I want it to stay a 20-amp circuit?


Yes, it does.

The overcurrent protection is for 12 gauge wire, if you put 14 in there it will not be properly protected.


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## InPhase277 (Feb 9, 2008)

red86yota said:


> Hi,
> I'm doing a renovation, and the building department wants me to put hard wired smoke detectors in the house. I'm planning on feeding the smokes from the master bedroom light circuit. The MB light circuit is 12-2 and on a 20-amp breaker. Does this mean I need to use the same guage wire for the smokes if I want it to stay a 20-amp circuit? 12-3 just seems like a bit overkill for the smokes...
> 
> Thanks!


Is it permissible to put the smokes on the circuit with the lights in the first place?

If so, then yes, you must use the same wire size as the circuit, that is, #12. If you want to use #14, then you must change the breaker to a 15 amp.


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## jcalvin (Feb 6, 2008)

Use 12 on everything. Nothing more aggrivating than having to keep up with the extra roll of wire and breakers. In almost every home I have been a part of, the owner has wanted to add something at the end of the project. It has worked out well for me having the extra ampacity to splice into an existing circuit and not be near overloaded.


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## CowboyAndy (Feb 19, 2008)

red86yota said:


> Hi,
> I'm doing a renovation, and the building department wants me to put hard wired smoke detectors in the house. I'm planning on feeding the smokes from the master bedroom light circuit. The MB light circuit is 12-2 and on a 20-amp breaker. Does this mean I need to use the same guage wire for the smokes if I want it to stay a 20-amp circuit? 12-3 just seems like a bit overkill for the smokes...
> 
> Thanks!


While you are adding them, you may want to make them combination smoke/co detectors... worth the few extra bucks.

Just make sure that if you are adding multiple interconnected smokes they are all the same brand. dissimilar brands can cause false alarms.


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## red86yota (Nov 26, 2008)

thanks for the advice and replies.

I was leaning towards getting a CO / Smoke detector for the basement....I guess I'll take a look at the prices and see how much more it would be to do the other locations as well. We have a small house, only 5 detectors total....

And I read somewhere that it was suggested to put the smokes and MB lights on the same circuit so that you would be more likely to know if the smokes CB was tripped... I'm trying to get ahold of my elec inspector to verify, but they aren't the easiest to get ahold of.

thanks again


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## theatretch85 (May 17, 2008)

If it isn't too much work, you could always run a new circuit just for the smokes and the master bedroom light, keeping the bedroom outlets on the current 20 amp circuit. This way you could run 14 guage wire for everything and still have a light on the circuit to indicate if the breaker has been tripped. You don't need to worry about the existing 12 gauge wiring run to the master bedroom light, just remove all the wiring for the outlets in the room and put this in a new junction box (since I am assuming most of the outlets are wired out of the light box in the ceiling). Its 'Ok' to have 12 guage wire on a 15 amp circuit, but its not ok for 14 gauge wire on a 20 amp circuit.


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## red86yota (Nov 26, 2008)

my inspector called me back, and they require the smokes to be on a dedicated AFCI circuit. This can be 15-Amp, so the 14-3 will suffice.

thanks for the comments


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