"Integrating" Kidde Smoke Alarms?

I have hard-wired, interconnected, Kidde Smoke Alarms (5). I want to create an alert capability through Hubitat and Pushover. I'm trying this device (photo), a relay made by Kidde for this purpose.

I am using an Ecolink contact sensor due to the convenient screw terminals.

The relay has a common lead and a lead for "normally open" and a lead for "normally closed". I'm thinking since this is usually a door/window sensor, I should configure using the "normally closed" lead and alert on an open condition.

Does this sound right? Has anybody else done this? Better ideas?


Actually you want the normally open and the common wires on the kidde relay connected to the ecolink sensor’s external inputs.

I believe the reason is that electrically speaking, you want this circuit to be “normally open” meaning that it’s default state is such that the circuit is not complete. When the smoke detector goes off, the relay closes, allowing a circuit to be completed via those external contacts on the contact sensor, indicating that a “door” has “opened.”

Several people have done this in the ST forum over the years, but this thread had the most detailed walkthrough. Worked fine for me!

Edit: I think that the contact sensors function the same way when used with the magnet on a door or window. The reed switch inside the sensor is held in a “normally open” position by the magnet when the door or window is closed. When the door opens and the magnet moves away from the sensor, the reed switch closes the circuit and the sensor sends an “open” event. It’s kinda confusing...

Wow, what a comprehensive write-up. Thanks for the link!

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I don't have CO alarms so I only had to deal with one relay and one sensor. Similar situation, I had a smoke alarm quite close to an unfinished area in the basement.


I’m jealous, I had no choice but to cram the relay into the tiny metal junction box that fed one of my smoke detectors and snake some thin-gauge wire out from the bracket to the sensor that I fastened to the ceiling nearby. I live in an apartment, so no attic or basement access to wiring for me.

Eventually when I swapped out the detector for a newer model with 10-year battery, I decided the thought of that little box being stuffed like that made me uncomfortable enough that I pulled it out. I bought an ecolink firefighter instead, which installs a few inches away from a dumb detector and listens for smoke or CO alert patterns (which are standardized in the US).

I did a little testing with the Ecolink contact sensor. The reed switch is actually open (not connected) when the magnet is not actuating it. The reed switch is closed when the magnet is next to it. So, for this particular sensor, switch closed=door closed and switch open=door open.

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I would also convert the sensor to have wired power so you don't have to be concerned about its battery level. Especially if you are triggering sirens. Do also heed the warnings of past experiences from @srwhite where auxiliary warnings failed to trigger.

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Agree with both points. This is purely optional to provide a little more awareness. Ultimately I am thinking about converting as many contact sensors as possible to Konnected.io. I can't do them all but I have access to some of the doors and windows from the unfinished basement area and attic space.

Which contact sensors are you considering? I’m doing a new build...

I haven't picked out any wired contact sensors yet. The only ones I have are the two sensors on my outdoor gates to the backyard. Those are Honewell 951WG and I am happy with those. Very sensitive switch and powerful magnet. I have those connected to Ecolink Z-Wave door/window sensors that are inside the house.

Here's a link to the Honeywell wired switches: https://www.amazon.com/gp/product/B016C2PZKY/

And a link to the Ecolink sensors (I use these because of the convenient screw terminals for external switches):

Thank you! I figured out I need 30 window sensors, 30 door sensors (interior included), and 20 motion sensors.

My house has eight smoke detectors and I am in the process of integrating them into my Konnected/Hubitat setup. Bought the Kidde SM120X and a combination CO/Smoke detector to put in the first detector in the basement, photo shown.

I doubt the Kidde interface will fit in the metal box, so I am thinking of adding a plastic box next to it for the interface and the Z-Wave alarm sensor that is supposed to have a NO switch option. I've ordered a "Aeotec Z-Wave Plus v2 Door / Window Sensor 7 Pro, Gen7" for the purpose.

I can't imagine this meeting code when I'm done. Does anyone have advice on code or do I plan on removing the thing when I do some work requiring inspection.

I am not a licensed electrician but here is my setup and a local inspector didn’t have any issues with it 5 years ago when this was modified by adding another smoke with an addition.

The relay has both high and low voltage so be sure to use proper cabling. Then exposing the contact outside should be fine.

This is an area that has gotten pretty particular "code wise" over the last decade in many municipalities. Many adopting HARDWIRED or FAIL-SAFE WIRELESS interconnection, MULTIPLE units on different levels, and one triggering causing ALL to sound. I doubt there's any "if you have a super duper spiffy Hubitat system on UPS unifying all alarms this supersedes lessor basic installations outlined in the code".

Even if your municipality has not gone that route yet ....I'd say to configure this in a way that you do not disable it's standalone functionality. You can just about bet your life an inspector would go wild on any HA that messes with certified code required safety devices. Actually, if you want them to ignore something else, then leave it installed so he/she can spend one page of their report making a big deal about your hacked fire sensor. :rofl:

That includes the powering of it, AS manufactured. I fully understand the impulse to do away with the battery but....I believe even the house powered ones have an onboard battery.

Thinking about fires, it's not uncommon for breakers to be tripped or power to be out (severe cold snap) and/or a fireplace going when a house fire starts. So I think cutting out the battery would be a no-no ...as much as I HATE all the HA batteries I now have to manage.

Bottom line, in the interim it's going to be your insurance company that you'll REALLY want to satisfy; a) for discounts, and b) for claim review when they want to challenge something.

I like the tree you're barkin up with this idea. I'm opting to keep looking for the ZigBee sensor that will satisfy my needs and has the proper certifications.

Don't know if the local code now requires a UPS on the smoke detectors, but they must be interconnected as are mine. A UPS wouldn't make much sense as they all have batteries. The Hubitat and all essential network gear is on a UPS.

My big worry was exposing the wires from the pictured metal box to the box that will contain the interface relay, even if only an inch or less. I'll follow the photo guidance from Michael on that, but I may add shrink wrap where the wires enter the box.

I'm also going to replace all my existing detectors to the same brand as they recommend, though the interface signal appears to be a standard. It is only a few years earlier than their lifetime and I need to replace the batteries anyway.

I was not aware of the CO120X when I was shopping, my Kidde combined CO/Smoke uses the same 3 wire connector as the old smokes. I'll look it up just to know.

I was also concerned about placing the Z-Wave sensor interface exterior to the blue box. I'll keep them outside for battery access as well. I like keeping everything labeled.

Note to PunchCardPgmr, my first job was Fortran on CDC Cybers. Loved those CDC card readers, but we moved to DEC stuff, 36 bit.

Thanks for the feedback. Gives me a little extra confidence to move forward.

There is also this but not sure about the false positives. I think @aaiyar may use them.

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They’re fantastic.

I don’t bother with smart smoke detectors or wiring in relays anymore (I’ve done both previously). Just standard dumb detectors and these ecolink firefighters. If the detectors have standard wired interconnects, you only need one firefighter.

Never had an issue with it alarming falsely. It’s supposed to be placed within a few inches of the device it’s listening to.


Having mains powered interconnected smoke alarms is now the standard and any new home built in Canada will come with smoke detectors installed in this manner. This includes one interconnected smoke detector in each bedroom. A large home may have many interconnected smoke detectors. This is building code in Canada. Many people choose to install smoke detectors that are also Carbon Monoxide detectors, this takes care of two monitoring requirements with one device.

Some people (myself included) have upgraded their older home to this new building code standard. Kiddie and First Alert are two of the major manufacturers of these detectors, they both supply relay kits for their mains powered interconnected smoke alarms. One manufacturer states the purpose of these relays are to: "activate auxiliary warning devices such as external bells and sirens, hallway or stairway lighting". Obviously an individual with a HE is simply concerned about the relay notifying HE of the smoke/CO alarm. I do this by connecting the relay to a Zooz Zen16, but it can be done by connecting the relay to any contact sensor, or using an hubduino solution.

Installing a manufacturer supplied relay on the interconnect wiring of your smoke alarms does NOT violate any code. Building inspectors take no issue with it, since it in no way disables its standalone functionality.

People considering going this route should be aware that First Alert only makes one relay that will notify you when either a smoke or carbon dioxide condition is present. With this First Alert relay you have no way of easily determining whether the alarm is due to smoke or carbon monoxide (I believe there is an hubduino solution to this, but it is not straightforward). With Kiddie, there are two relays that you can install on your interconnect wiring. One relay will notify you of the smoke alarm and the other will notify you of the CO alarm.

In my opinion, having these relays are the best way to notify your HE of a smoke or CO alarm. But each to their own.

Remember both well, throw in a touch of NCR (yes the cash register company), Sperry-Univac, and HP too. We best not start this here, people WILL start coming out of the woodwork for nostalgia's sake. :partying_face:

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I have had a good experience with the Ecolink. I did not want to fiddle with a reliable smoke detector install, and the Ecolink has reliably triggered in every test with my Kidde smoke alarms, with no false positives since I purchased it almost 2 years ago.