Connecting Low-Voltage Smoke Detectors

Some home security systems are connected to low voltage wired smoke detectors which are wired directly to, and powered by DC voltage from the alarm panel. Common brands of this category of smoke detectors are System Sensor, Interlogix/ESL, DSC, and Bosch.

 DO NOT USE KONNECTED WITH CRITICAL FIRE AND LIFE SAFETY EQUIPMENT

Konnected is NOT designed for use with fire and life safety equipment, and cannot be used with low-voltage smoke detectors to meet minimum fire safety requirements in the U.S.

Use with low-voltage smoke detectors is for ancillary notifications and home automation purposes only, and is only acceptable if there are other independently functioning smoke alarms on the property that can notify the occupants in an emergency.


4-Wire Smoke Detectors

Low-voltage smoke detectors that have 4 separate wired connections on the back are often able to signal Konnected without any additional equipment. These smoke detectors generally work just like motion sensors: 2 wires (red & black) supply 12VDC power, while a second pair of wires (any color) make a Normally Open (NO) circuit loop that closes when smoke is detected. When multiple smoke detectors are interconnected in-parallel, if any one of the smoke detectors alarm, the circuit is closed.

Standards-compliant 4-wire smoke alarm installations will include an end-of-line resistor and power supervision relay that enables a standards-compliant panel to detect wiring faults and/or power faults. The Konnected Alarm Panel is not standards compliant and cannot be used to detect faults.

However, the Konnected Alarm Panel can detect the simple open or closed circuit when connected directly to the Normally Open signal loop to signal a smoke alarm detection to your smart home platform. This is a non-standard use of these smoke detectors and this connection method does NOT meet fire safety standards in the U.S.

Powering Low Voltage Smoke Detectors

4-wire smoke detectors wired to the Konnected Alarm Panel will share power with the Konnected device, your other wired sensors, and siren. Ensure that you use the 12V power supply that comes with your Konnected kit, and test that you have adequate power by sounding the siren and testing the smoke detector simultaneously. 

A backup battery should be used to ensure that your smoke detectors still work in the event of a power outage.

Connecting Directly to the Konnected Alarm Panel

Connecting the red/black pair of wires to the AUX +/- respectively to power the smoke detector with 12V DC. 

Remove the end-of-line resistor and power supervision relay wired at the last smoke detector in the chain (WARNING: This disables any fault detection!). Then, connect the signal pair to any zone and G on the Konnected Alarm Panel board. By default, Konnected assumes a NC circuit. Most smoke detectors are NO, so set the "inverse" option when setting up your smoke zone so the status appears accurately in your smart home app.

Connecting via an Interface Module

System Sensor makes the System Sensor COSMOD4W interface module for System Sensor brand 4-wire smoke and CO detectors that simplifies the installation, maintains the fault detection and interconnection feature of standards-compliant installations, and adds a dedicated 95 dB sounder for the smoke detectors.


2-Wire Smoke Detectors

Some traditional alarm systems panels are connected to 2-wire smoke detectors that are powered by a special smoke zone supplying supervised 12V power. 2-wire smoke detectors carry power and signal over the same pair of wires by using a special polarity reversing switch to indicate an alarm. Unfortunately, these will NOT work with Konnected.

2-wire smoke detectors will NOT work directly with Konnected. See below about possibly using with an interface module.

Popular smoke detectors models that fall into this category and DO NOT work with Konnected are System Sensor 2W-B, 2WT-B, COSMO-2W and Interlogix 521B, 528B. If you have this type of smoke detector, all hope is not lost! Inspect your wiring. If you have a 4-conductor wire running from your smoke alarm location to your alarm system panel location, you may be able to replace it with a 4-wire model and use the existing wiring or use a compatible interface module.

Connecting via an Interface Module

System Sensor makes the System Sensor COSMOD2W interface module for System Sensor brand 2-wire smoke and CO detectors that enables you to use the existing 2-wire smoke alarms. It provides discrete output zones for smoke and CO that can be connected to a Konnected Alarm Panel zone. It also adds a dedicated 95 dB sounder for the smoke detectors.

Recommended 4-Wire Smoke Alarms

Konnected users have reported success with the following smoke alarm models. If you have 4 low-voltage wires running from your alarm panel location to each smoke detector location and your smoke detectors need to be replaced due to age, incompatibility, or lack of built-in sounder, these models may serve as good replacements. All smoke detectors on this list meet the following criteria:

  • Built-in sounder (alarm)
  • Operate on 12VDC
  • Built-in Form A or Form C relay for signaling Konnected

Did you find it helpful? Yes No

Send feedback
Sorry we couldn't be helpful. Help us improve this article with your feedback.