How Do I Add a 2-Wire Smoke Detector to My Wireless Alarm System?

You cannot add a 2-wire smoke detector to your wireless alarm system. A 2-wire smoke can only be used on Zone 1 of a hardwired alarm system. This zone uses special logic that is required for a 2-wire smoke to function properly. However, a wireless panel can interface with 4-wire smokes.

When a wired smoke detector is activated and a fire alarm occurs, the device must be reset. This will clear the alarm and stop the smoke detector from sounding. A 2-wire smoke detector does this in a somewhat unique way. The device is set up with Zone 1 on a hardwired security panel. In the event of a fire alarm, Zone 1 will instruct the 2-wire smoke to automatically reset itself after the panel has been disarmed twice. These are special instructions exclusive to Zone 1 on a hardwired system. These instructions allow a 2-wire smoke to be used on a hardwired system, without using a power relay or an on-board trigger. By contrast, 4-wire smokes do not comply with these instructions. Therefore, a 4-wire smoke cannot be used with Zone 1 on a hardwired system, and these devices will require a power relay or an on-board trigger in order to be reset after a fire alarm.

But any hardwired zones that exist on a wireless system do not function in the same manner as Zone 1 on a wired system. A wireless system will never have a zone that provides the current needed, or utilizes the special instructions found on Zone 1 for a wired system. In other words, a 2-wire smoke would have absolutely no way to operate or reset itself if used with a wireless system. For that reason, wireless alarm systems are designed to be incompatible with 2-wire smokes. The easiest solution for users of wireless alarm systems is to simply use wireless smokes in their setups. Remember, any wired zones on a wireless alarm panel cannot be programmed for life-safety devices.

However, some users may want to use hardwired smokes with their system. For example, they might have pre-existing hardwired smokes. Or they might want to create a setup in which if one smoke activates, all smokes will sound. This is possible using certain 4-wire smokes. To use 4-wire smokes with a wireless system, the user will need a transmitter that allows for a normally open zone with an end of line resistor (EoLR). Multiple 4-wire smokes can be set up with the same wireless transmitter, much in the same way that 4-wire smokes would be set up with a hardwired zone on a wired system. One example of such a transmitter is the Honeywell 5817CBXT.