Zooz ZEN55 in Home Assistant: smoke and CO alerts from existing alarms

The smoke alarms already know how to make a racket. Give Home Assistant the useful follow-up: turn on the lights, send a phone alert and, if you choose, unlock a specific exit.

Zooz ZEN55 is the pick when you want those extras from compatible wired, interconnected smoke and CO alarms you already own. It reads their analog interconnect signal and reports it over Z-Wave. It doesn’t listen through a microphone.

ZEN55 supplements, never replaces, your listed smoke and CO alarms.

Compatibility and setup guidance come from Zooz, Home Assistant and the Companion app documentation; this is a research-based guide.

First, meet the interconnect

The important shopping question is behind the detector, not on the Wi-Fi box. You need a compatible analog alarm interconnect, plus mains power and neutral for the ZEN55. A collection of battery-only wireless alarms is a different project.

Zooz says it has tested analog interconnected alarms from First Alert, Kidde and BRK. Match your exact alarm and signalling method rather than shopping by brand alone. If the model’s instructions don’t identify a compatible analog interconnect, send its model and wiring information to Zooz before choosing the bridge.

Use Zooz’s when-to-use guide and ZEN55 manual for that fit check.

Your starting point	The useful decision
Compatible wired analog smoke/CO interconnect	Add ZEN55 to bring the shared alarm signal into HA
Battery-only alarms with wireless linking	Choose a different interface; ZEN55 needs mains power and the appropriate wired signal
Unclear or proprietary interconnect	Identify the exact model with Zooz before buying
You want the originating room on the phone	The shared signal doesn’t carry the identity of the detector that started it
You want HA to silence or activate the detectors	ZEN55 receives their signal; it cannot turn the smoke alarm on or off

That last distinction is useful: the detector sounds the alarm; HA reacts to the report. The Zooz FAQ explains how it separates smoke and CO signals and why the shared interconnect doesn’t identify the first detector.

Buy the bridge, then choose one radio

Already have working Z-Wave in Home Assistant? Start with the ZEN55 alone. You don’t need another controller for this one device. Zooz explicitly lists Home Assistant with Z-Wave JS as supported.

Starting fresh? Choose Home Assistant Connect ZWA-2 as the official hardware route. Our Z-Wave setup and first-device guide walks through the controller side. The ZWA-2 maker page describes the hardware.

Zooz ZST39 LR is the alternative USB radio, not an extra piece to buy alongside ZWA-2. Use the Zooz hardware documentation and the HA Z-Wave JS documentation for supported software and firmware. HA recommends current 800-series adapters with firmware 7.23.2 or newer.

You will also use your existing HA host, a supported light entity and the Companion app on your phone. A smart lock is optional. The example below assumes those devices are already added to HA; its entity names are examples to replace with yours.

What the little bridge can—and can’t—do

ZEN55 sends different reports for smoke and carbon monoxide. One bridge can pick up a compatible interconnected network’s signal, so you can build different messages later without replacing every alarm.

It also has an optional output relay, which is separate from reading the alarm input. This guide leaves that relay unused and uses existing HA-controlled lights instead. Keep the alarm power feed independent of that optional output; the installer should follow the current manual’s monitoring-only diagram.

The product overview describes the bridge and relay roles. ZEN55 is not a new smoke or CO sensing element, and its output does not give HA a detector silence button.

The local part is ZEN55 → your Z-Wave controller → Home Assistant. Z-Wave JS is a Local Push integration. Lights and locks can then use their own local integrations. Phone delivery is a separate leg: the Companion app’s notification service and your phone’s connection still matter. Test that leg as well as the sensor report.

For intrusion arming, entry delays and contact sensors, use our Alarmo guide. Keep smoke/CO reactions independent of whether Alarmo is armed: an alarm deserves the same response during a quiet afternoon as at bedtime.

The wiring plan belongs with the installer

Have a qualified electrician install the ZEN55 using the current Zooz manual, with circuit power off at the breaker before wiring work.

The planning view is simple: line and neutral power the module; the alarm interconnect supplies its low-voltage signal. The optional relay leads are handled as shown in the monitoring-only diagram, rather than improvised into the alarm feed.

Zooz suggests the last detector box in the series because it usually has fewer wires and more room. Zooz also permits another detector box; let the installer choose the suitable location. Give the installer the alarm model, the current manual and the intended monitoring-only job.

Keep the module’s SmartStart QR code available for pairing. The manual puts the code on the back of the device, so plan the scan before everything is closed up.

Add ZEN55 to Home Assistant

1. Set up Z-Wave JS and your chosen adapter using the Z-Wave guide.
2. In the current HA interface, open Settings → Connectivity → Z-Wave → Add device.
3. Choose Scan QR code for SmartStart. Follow the ZEN55 sequence: scan while the module is unpowered, then have it powered for inclusion. It supports S2 Authenticated inclusion.
4. Let the device interview finish. Open its device page and find the actual smoke and CO alarm entities. Don’t select the relay switch or the node-status diagnostic as the alarm trigger.
5. Follow the detector maker’s test procedure and watch which entities change. Name them clearly and copy their entity IDs into your automation.

The Z-Wave JS inclusion instructions and Zooz manual cover SmartStart and the manual-inclusion alternative. Finish this real signal check before building the light show.

Lights up, phone loud, exit by choice

Build one automation that reacts when either the smoke or CO alarm binary sensor changes to On. In the editor, use State changed triggers and choose the actual alarm entities you just tested. The YAML below uses example IDs.

This example turns a dimmable light to 100%, then sends an iPhone critical notification. The optional exit-unlock action is included but disabled until you choose to use it.

alias: Smoke or CO - lights and critical alert
triggers:
  - trigger: state
    entity_id: binary_sensor.zen55_smoke_alarm
    to: "on"
  - trigger: state
    entity_id: binary_sensor.zen55_co_alarm
    to: "on"
actions:
  - action: light.turn_on
    continue_on_error: true
    target:
      entity_id: light.exit_path
    data:
      brightness_pct: 100
  - alias: Optional - unlock the chosen exit
    enabled: false
    action: lock.unlock
    continue_on_error: true
    target:
      entity_id: lock.chosen_exit
  - action: notify.mobile_app_your_iphone
    continue_on_error: true
    data:
      title: Smoke or carbon monoxide alarm
      message: An interconnected alarm has triggered. Follow your alarm's emergency instructions.
      data:
        push:
          sound:
            name: default
            critical: 1
            volume: 1.0
mode: queued

Use a light that supports brightness; this example sets it to 100%. HA’s light actions document brightness_pct. The State changed trigger explains to: "on"; leaving out from also lets an alarm report arriving from an unknown state trigger the automation.

Choose exit unlocking deliberately. Set the optional action to the specific door you want, enable it only if that is your intended response, and press Save. The lock integration documents lock.unlock. This recipe doesn’t automatically relock the door after the alarm clears.

continue_on_error lets the next action run after an ordinary action error, so a failed light command doesn’t stop the phone attempt. HA documents that option and disabled actions in automation building blocks.

Make the phone part genuinely loud

The iOS payload above comes from the Companion critical-notification guide. It requests the default sound as a critical alert at full volume, including when the phone is muted or in Do Not Disturb. Allow the app’s notification permissions and test that behaviour on your phone.

Android needs its own payload. Use the Android examples on that same page for immediate delivery, alarm-stream sound and channel/DND settings. Don’t paste the iOS sound block and expect it to configure an Android notification channel.

Test the whole chain, not just the message

Start with the exit-unlock action disabled, then press Save. Use Run actions to test the light and phone delivery. That checks the actions, not whether the alarm can trigger them.

Next, warn anyone nearby and use the detector maker’s test-button procedure. Watch the ZEN55 alarm entity change, inspect the automation trace, and verify the light and critical notification. Zooz says a combination alarm’s test can exercise both smoke and CO; follow the sequence for your particular detector and verify both reports where supported.

Let the alarm return to normal and watch the HA entities clear. Repeat the supported test so you know a later alarm can trigger another run. If you chose exit unlocking, enable that action, press Save, and include the selected lock in a supervised repeat test.

Keep the result simple: your existing alarms sound, HA brings up the lights, and your phone gets the extra message. Then explore the Home Assistant hub for the next useful project—not another app you have to remember to open.