What is the total number of smoke alarms or devices I can interconnect?

Twenty-four. The NFPA 72 standard states the interconnect limit is 12 smoke alarms and up to 6 other alarms (heat or carbon monoxide) for a total of 18 alarms. With 18 alarms interconnected, up to additional 6 relay modules may be interconnected (for a maximum of 24 devices).
If battery backup alarms and non-battery backup alarms and accessories are mixed in an interconnect system, all devices without battery backup WILL NOT operate during an AC power failure.

CAUTION: USI alarms and accessories should only be interconnected with other USI alarms and accessories. Connecting devices from another manufacturer to USI devices may result in nuisance alarms, failure to alarm, or damage to one or all of the devices in the interconnect system.

All interconnected USI alarms should be powered by the same fuse or circuit breaker. Smoke alarms shall not receive their power from a circuit that is protected by a ground fault circuit interrupter. Improper connection will result in damage to the alarm, failure to operate, or a shock hazard.

« Back To FAQs List