Security & Fire Protection Systems/Replacing hardwired smoke detector


I have a 3 unit hardwired system made up of Firex Model G-18 smoke detectors.  Can I replace one of them with a BRK 9120B?  The directions are not clear.  Neither of the two adaptors that came with the BRK fit the Firex harness hanging from the ceiling.  I could just remove the harness at the wirenuts and tie in the BRK but I don't know if everything is compatable.

Can you help?

The BRK unit is NOT compatible with the Firex smokes.  You'll have to replace ALL of the smoke alarms with units compatible to each other.  The installation instructions will give you a list of compatible model numbers (usually all from the same manufacturer).  You are going to have to change the wiring harnesses if you're going from a Firex smoke to a BRK one.

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Frank Kurz


Questions relating to Burglar Alarm and Security Equipment, Fire Alarm and Extinguishment Systems, Access Control, CCTV Systems, Installation, Service, Testing, Verification


30 years installing, servicing, and testing security, access control, extinguishment, and fire alarm systems

Chair of ULC Working Groups for Fire Alarm Testing (CAN/ULC-S536) and Fire Alarm Verification (CAN/ULC-S537), Executive Director of the Fire Protection Technicians Network (

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Associate in Science; Emergency Systems (University of British Columbia); Aircraft Maintenance Technology (BCIT)

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