I am adding a smoke detector and I am interconnecting it with the detector I already have. They are "hard wired" detectors with battery backup and they have a yellow wire for interconnection. I have attic access to run wire from the existing electrical box to the new one. I need three wires from the old box to the new - two (black and white) for power and one for interconnectoin. Sounds easy enough, I can run a 14-3 w/ground NMB and use the red wire to connect the detectors.

But, in the NEC 2002 (which doesn't mention smoke detectors - only Fire Alarm Systems in Article 760) I am stumbling over 760.26 which appears to prohibit power supply and fire alarm circuit conductors in the same cable, enclosure or raceway. The conductors are not connected to the same equipment because the equipment the power supply conductors are connected to is the service panel. Do I need to run 14-2 w/g to the box and a seperate interconnecting wire not in the non-metallic sheathed cable? If so, how does it enter and secure to the plastc boxes I am using?

 

I applaud you for looking at a code book although I don't agree with your interpretation.
760.26 states that Class 1 (120V power wiring) and non-power limited fire alarm circuits (interconnecting wire) shall be permitted to occupy the same cable, enclosure or raceway as long as they are properly insulated for their voltage levels. 14/3 NM-B cable (romex) is rated to handle the voltages at hand.
Your covered. Maybe it was a hang up with terminology.

 

Yes, it is much about terminology. I am finding more info in NEC Article 725. Normal house wiring Circuits are Branch Circuits and NOT Class 1 (which are defined under 725.2). Unless, is a Branch Circuit a Class 1 if there are any signalling devices on it, anywhere?

The closest point of closure seems to be in 725.26(B)(1) "Class 1 circuits and power supply circuits shall be permitted to occupy the same cable, enclosure, or raceway only where the equipment powered is functionally associated." This appears to be my circumstance.

Anymore thoughts? Thanks for your help!!

 

[ Maybe it was a hang up with terminology. [/B][/QUOTE]

Yes, it is much about terminology. I am finding more info in NEC Article 725. Normal house wiring Circuits are Branch Circuits and NOT Class 1 (which are defined under 725.2). Unless, is a Branch Circuit a Class 1 if there are any signalling devices on it, anywhere?

The closest point of closure seems to be in 725.26(B)(1) "Class 1 circuits and power supply circuits shall be permitted to occupy the same cable, enclosure, or raceway only where the equipment powered is functionally associated." This appears to be my circumstance.

Anymore thoughts? Thanks for your help!!

 

Class 1 circuits are a similar class as branch circuits. Same as same.

 

Just FYI: Smoke detector requirements are not in the NEC. The are covered by the National Fire Alarm Code, NFPA 72 (section 2-2.1.1.1 specifically). The NEC is NFPA 70.

 

Although the wiring requirements for smoke detection devices are in the NEC (NFPA 70).