First Alert Combination Smoke & Carbon Monoxide Alarm, Interconnect Hardwire Detector with Battery Backup, SMICO100-AC, 1-Pack

Reliable & Reputable Detectors!
I have been a master electrician for 32+ years. If you’re not 100% sure of what you’re doing, hire a professional!Ok a lot of people are complaining about the new connector. It literally takes 60 seconds to rewire. I rewire anyways so I can put a meter on the ceiling wires to make sure everything is as it should be. The base is a tad smaller than my previous ones. They were from a different company though. It presented zero issues during the installation. I have 3 detectors upstairs and one in the basement. I wired them all and they all worked inline perfectly. When one goes off, they all go off. The alarm is very loud and high pitched. It also tests both the smoke and CO² detectors when pushing the test button. You’ll get a beep and then another beep. Then it repeats. Meaning they are all working. Bonus each detector comes with a pre installed Duracell 9 volt battery. You also receive a dust cover for the detector if you need to work in that room. Kicking up dust or debris can get inside the unit and fault it. Nice little freebie to have. Although I didn’t need, they come with very detailed instructions with diagrams. After I installed them all I tested it my way using certain techniques to get both detectors to alert. They passed on both smoke and CO². For this price point, I am very happy with these units. It gives me a sense of security knowing my family is protected. Please mark the back of your detectors with the date you install them. I use a black marker. Also be sure you were shipped the correct units. It should say on the outside label Combination Smoke/Carbon Monoxide Alarm. I’ve posted pictures along with a video. I hope this aids with your decision whether these are for your home or not. I will update again if I have any issues in the future. As of now they are working as they should and I again, am very happy with my purchase.

Exact Match and Flawless Swap
Replaced my old hardwired Smoke and Carbon Monoxide detector with the same model, and installation was incredibly easy. I just twisted off the old unit, unplugged it, plugged in the new one, and twisted it into place. Everything fit perfectly and worked right away. Great replacement.

A Good Replacement for the SC9120B
I bought this to replace the six First Alert SC9120B alarms my builder installed about eight years ago. These were very easy to install taking less than five minutes each. I did have a few issues with some of my older models though. The builder put so much wire in some of the junction boxes that it pressed down hard on the alarms making a strap wrench, or a belt, necessary to unscrew them. Also, on one of the units, they used a screw that was too large to secure the mounting plate but there was enough room to wiggle the old plate out.A few notes…This is a direct replacement for the SC9120B but it isn’t a one-to-one match physically. You will need to install a new mounting plate. The good news is that the screw holes on the new model are universal, so they should fit most junction boxes and is very easy to install.The power connector is the same, but the receptacle on the new alarm is smaller. It does help to prevent bent pins, but you need insert the connector straight for it connect securely. When removing it from the SC9120B, I found a pair of pliers useful to get a good grip.Although the units are hardwired, they do come with battery backup using a preinstalled 9V battery. This battery is an ordinary Duracell 9V model and will likely fail in about five years. For hard to reach alarm locations, you may want to get a ten-year battery and replace them. Again, these are battery backups for hardwired alarms, so they really shouldn’t be needed very much, unlike battery-powered alarms.Like the prior model, this alarm has a green LED that indicates it’s plugged in and functioning normally. That LED is about 25% to 50% brighter than the one on the SC9120B and will light up the area around the alarm at night. Most of the light seems to leak out the “Ring” at the top of the alarm right above the indentation. It is possible to put something in that “Ring” to block the light, such as electrical tape, or, if you’re the adventurous type, open up the alarm and use a black marker to dull the LED or snip the LED entirely. Given that the LED serves as an indicator telling me it’s working as intended, and in my case, I’m planning on selling my home during the expected lifespan of the alarm, I’m opting for electrical tape.

Replacement unit
Needed to replace a unit that failed. This was noted as the replacement since they no longer produced the ones we have in our home. We were hoping to just attach the unit, but we had to remove the existing base so the new unit would fit. It was very easy even at 12’ in the air. Once the new base was screwed to the ceiling, the new unit plugged right in. No problems at all…easy to install.

Excellent for the price easy to install would buy again exactly what’s described comes with batteries hardwired would not hesitate to buy again excellent deal

Our older model of these were about 8 years old and didn’t have the replaceable battery so when they started beeping randomly here and there, we had no options but to change it up. It is nice how easy these are to replace for a hardwired option when the mounts are the same. This was the best place to buy them cost wise.

Previously had same manufacturer device including strobe but got tired of reparative nuisance alarms and replacements. So far new ones without strobe are operating properly