Dwelling 120-Volt Smoke Detector Wiring

[shortcircuit2]

I have a large 1-family dwelling with an existing hard-wired 120-volt smoke detector system. Now, a large addition to the existing dwelling will now require more that 12-smoke detectors which triggers the need for a fire alarm system.

Can the existing 14/3 Romex be used for a Class B SLC alarm circuit and install System Sensor smoke alarms via "pig-tailing" at each existing 14/3 hardwired outlet box without addressability? It appears this arrangement will also involve t-taps at some locations due to common existing 120-volt smoke detector wiring practices.

I searched forums but found now discussion of this situation.

 

[gadfly56]

I have a large 1-family dwelling with an existing hard-wired 120-volt smoke detector system. Now, a large addition to the existing dwelling will now require more that 12-smoke detectors which triggers the need for a fire alarm system.

Can the existing 14/3 Romex be used for a Class B SLC alarm circuit and install System Sensor smoke alarms via "pig-tailing" at each existing 14/3 hardwired outlet box without addressability? It appears this arrangement will also involve t-taps at some locations due to common existing 120-volt smoke detector wiring practices.

I searched forums but found now discussion of this situation.

It isn't clear what your intention is with the existing smoke alarms. They would have to all be replaced with the System Sensor smoke detectors. I assume you're going with a low-end Honeywell or similar panel and using the "SS" series detectors?

 

[tortuga]

A 'Household Fire Alarm System' requires a Fire Alarm Control Unit (FACU), which would need to be listed as such under UL 864 Control Units and Accessories for Fire Alarm Systems.
A FACU for a simple residential system need not be a huge red panel in the basement, my NFPA 72 is out of date but it says a
Fire Alarm Control Unit (FACU) is defined as:
A component of the fire alarm system that receives signals from initiating devices or other fire alarm control units and processes these signals to determine part or all of the required fire alarm system output function(s).

If one or more of the smoke alarms is a FACU then it would be possible to soft upgrade a residential system, even zone it.
I have not done any product research on this but glancing at all the smart home smoke alarms on the market like 'Nest Protect', I would not be surprised if a residential product that can just replace one interconnected smoke alarm exists that would cover the minimum requirements for a residential FACU.

 

[shortcircuit2]

It isn't clear what your intention is with the existing smoke alarms. They would have to all be replaced with the System Sensor smoke detectors. I assume you're going with a low-end Honeywell or similar panel and using the "SS" series detectors?

Yes to be clear the existing 120-volt smoke alarms will be removed altogether, and the 120-volt interconnection capped off.

Use a low-end Honeywell alarm panel with SS series detectors with the detectors pigtail connected (T-tapped) using the red and black of the 14/3 romex which results in unsupervised detectors. The detectors will still trigger the alarm but if any detector is removed the alarm panel will not know. Connected similar as 120-volt smoke alarms where if any detector is removed the others still work.