I’m sure this has been done before but I know I’ve seen lots of discussions on the best way to integrate existing smoke/CO sensors into SmartThings. After lots of research I did what I thought was the best way for my situation and figured I’d write up what I did in case it could help someone else. Cost me less then $100 and about 6 - 8 hours of work, probably less if I didn’t write this up and take pictures. The way I did it also does not interfere with the existing sensor operation which was my main concern.
My house was built two years ago and has sensors to meet code. That means smoke in each of the three bedrooms, a combination smoke/CO in the upstairs hallway, a smoke in the first floor hallway near the kitchen, and another smoke in the basement. They are all Kidde brand and interconnected. Because of this I wanted to see what I could do to tap into them without adding additional sensors. To that end Kidde makes a module that connects to the existing 3 wires (hot, neutral, and signal) that goes to each detector and give you a normally closed or open contact. So here was my material list:
1x Kidde SM120X Smoke Relay Module ($13 on Amazon)
1x Kidde CO120X Carbon Monoxide Relay Module ($12 on Amazon)
2x Ecolink Door & Window Sensors DWZWAVE2-ECO (2-pack for $54 on Amazon)
1x 4x4 electrical box (or bigger work box) and a cover ($4 at Home Depot)
Some 18ga or 20ga wire
Some 12/3 Romex to extend the nearest sensor to somewhere I can work with
I went with the Ecolink sensors because they have a input already on board. Perfect for wiring the relays to without anything special having to be done:
First I got kinda lucky that they mounted a detector about 4’ from my unfinished storage room so that’s obviously the sensor I tapped off of. If I didn’t have easy access I’d go up into the attic and tap off of the second floor sensor. I already have GE Z-Wave dimmers throughout the house so I wasn’t too worried about the signal getting through the house either way:
I started by pairing each EcoLink into SmartThings. Both were a PITA for some reason, both had to have the batteries pulled and retried twice. But they pulled in. So first thing once they were pulled in was testing those external connections, no use mounting and wiring if it doesn’t work. So I shorted them out and nothing happened. I put the magnet up to them and nothing happened then either. After fumbling with it I found that the tamper switch next to the LED will cause it to say “Open” whenever the case isn’t on it. So I held that down and tried again and the external contacts worked fine for open and close, almost instantaneous response. Once that was verified I felt confident in proceeding.
The Kiddie modules were identical to each other wiring wise except for one wire. Both had three wires to connect to the existing smoke/CO detectors (AC Hot, AC Neutral, and Interconnect Signal) and three more for the contact. The Smoke however had a extra 9v DC out which I would not be using. For simplicity I cut that wire (gray) short and the normally closed wire (yellow) as I would be using the normally open that closes on signal. I then tried to test fit them…it’s a tight fit but the shrink wrap they use is flexible on the ends, kinda keeps them in place:
I bought a white nylon cover plate so I could drill it for the wires to get to the EcoLink sensors. I figured they shouldn’t be jammed into the box with the 120v and would transmit better outside. So I laid them out and marked up the cover for drilling then mounted the bases to the cover plate. Thankfully the circuit boards can be removed relatively easily making it a lot easier:
The wires coming off the relays were a bit too big to get through the back cover of the sensor but I found 18ga wire to be a perfect fit:
After mounting and getting the wires through I had something that actually didn’t look half bad:
Next was to mount the box in the ceiling and get the wires run over to it. I knew it was going to be slightly tight in the box…in retrospect I should have went with a three gang box. The power and signal wire are wire nutted and it’s ready to have the sensors connected.
Once I connected the EcoLink sensors to the relay outputs I mounted the cover plate and it’s all done.
And here is the room in SmartThings
Now the only thing I may do is change the default device type and modify it to say “Normal” and “Alarm” instead of Open and Close.
Hopefully someone will find this useful.