is this legal

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PEDRO ESCOVILLA

Senior Member
Location
south texas
i was on an inspection, week one, owner/builder is doing the work, smoke detectors not properly interconnected by 12/3 romex, the fellow had used 12/2. I was about to open and say you had to use 12/3 when the "senior inspector" sasys 'you can just run a # 12 between 'em 'cause it's just a signal wire anyway'. I questioned it, bo said it was ok. sounds a bit scary to me
 

jumper

Senior Member
Not legal although 14/3 may be sufficient depending on circuit OCPD.

300.3(B) Conductors of the Same Circuit. All conductors of
the same circuit and, where used, the grounded conductor
and all equipment grounding conductors and bonding conductors
shall be contained within the same raceway, auxiliary
gutter, cable tray, cablebus assembly, trench, cable, or
cord, unless otherwise permitted in accordance with
300.3(B)(1) through (B)(4).
 

al hildenbrand

Senior Member
Location
Minnesota
Occupation
Electrical Contractor, Electrical Consultant, Electrical Engineer
The answer is not going to be found in the NEC. You will have to consult the local smoke detector ordinance to find the language the regulates how dwelling smoke detectors are to be installed.

The NEC regulates the installation of the branch circuit wiring that is used for line powered smoke detectors, but, whether they have to be interconnected and by what gauge of wire, is not in the NEC.
 

al hildenbrand

Senior Member
Location
Minnesota
Occupation
Electrical Contractor, Electrical Consultant, Electrical Engineer
Not legal although 14/3 may be sufficient depending on circuit OCPD.
The OP says the smokes are single station (not interconnected).

Where does the NEC say that more than a two conductor with ground is required?

Edit - Oops. That's signal wire, not single station. Sorry.
 
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al hildenbrand

Senior Member
Location
Minnesota
Occupation
Electrical Contractor, Electrical Consultant, Electrical Engineer
Pedro, since you say that this is an NM installation, note that 300.3(B)(3) allows the conductors to be run in multiple cables, and that they don't have to be grouped. One possible solution is to add another two conductor NM cable, and only use one of its insulated conductors for the signal interconnect.

The cable doesn't have to be a three conductor.

Using a single THHN running loose or thermostat wire, however is a no no.
 
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