I’m upgrading all of my hardwired smoke/CO detectors (replacing older Kidde models with new First Alert combo units), and I’m integrating a ZEN55 DC Signal Sensor for smart fire alarm detection via Home Assistant.
The ZEN55 manual states:
Install the DC Signal Sensor in the box with the last smoke detector in series, it will only have 3 wires in the box (usually black, white, and red).
I’m wondering — is this placement a requirement, or more of a recommendation for ideal conditions?
Since all interconnected detectors receive the same signal when one alarms, I would expect the ZEN55 to pick up that 9V interconnect trigger from any point in the chain. Is the “last detector” recommendation meant to:
Avoid feedback from upstream detectors?
Prevent false positives?
Ensure the cleanest or most isolated signal?
If I’m not 100% sure which detector is the last in the series, would placing the ZEN55 at a midpoint or another accessible box still work reliably, assuming it’s wired correctly?
Really appreciate any technical insight. I love the flexibility this device adds to hardwired systems and want to make sure I’m setting it up for the best reliability.
Hi @smartiez, great question! It’s simply a recommendation based on the space available. The last detector in the chain will have more space in the box due to fewer wires being present, so installation would be easier. It can install in any detector box in the chain. The device will work the same regardless of which box in the chain it is installed in.
FWIW, the ZEN55 works well in our home, even though it is not in the “last box,” but located in a more accessible location. (The last one in our house happens to be at the peak of a vaulted ceiling, which makes it clearly not the easiest place to install it or to reach it. ) In that location, it also serves as a repeater for nearby battery operated devices.
Mine is also not in the last box. I purposely put it in the box closest to the hub, as I have plenty of AC devices scattered throughout the house already (to act as repeaters).
Oh thank you for confirming this. I really spent awhile thinking about this.
I ultimately went through each box and looked for one that only had a single interconnect wire. But I actually found two like this! I chose the one on the first floor closest to the circuit breaker. And it all seems to work well.
It’s a great idea to use this placement strategically for the mesh network! I think I got lucky because the one I chose happens to be far from my hub so it’s doing a really good job repeating my first floor devices.
@Sara might I suggest an update to the help articles and the manual? I appreciate that you are looking out for us by suggesting a good placement based on free space in the electrical box. However the text makes it seem like there is an actual functional difference. It would have helped me at least to know that you were suggesting where I might find the most room in a box.
) In that location, it also serves as a repeater for nearby battery operated devices.