How to Wire a Duct Smoke Detector

Examine the smoke detector's wiring diagram. The wiring diagram, found on the detector's housing and in its manual, identifies and labels each terminal. Most duct-mounted smoke detectors have multiple input voltage options, often 24 ,120 and 240 volts. Duct smoke detectors also have two sets of low-voltage alarm-circuit terminals.

Determine the smoke detector's input voltage. The fire alarm system's control panel, located near the air handler, lists the smoke detector's input voltage and labels the control system's wire terminals. Usually two sets of wires extend from the control panel's wire terminals. One set leads to the smoke detector's input power supply and the other leads to the smoke detector's alarm circuit. In some cases, the smoke detector receives its input power from the air handler. Check the control panel's wiring diagram to verify the input power's source.

Connect the duct smoke detector's input power wire to the wire terminals with the correct voltage label. Loosen the wire terminals with a slotted screwdriver. Slip the wires into their respective terminals and tighten the screws.

Loosen the smoke detector's alarm-circuit terminal screws with a slotted screwdriver. Each smoke detector contains two sets of alarm-circuit terminals, one input set and one output set.

Insert the control panel's alarm wires into the smoke detector's alarm-circuit input terminals. Place the manufacturer-supplied resistor into the output terminals.