Replacing Three Smoke and CO Detectors

 Our Nest Smoke and CO detectors have started complaining that two of them -- the oldest two in the hallway and by the Master Bedroom -- need to be replaced.  They only run for 10 years, and then have to be replaced.  Even tho they are hard-wired into the electrical power.  

And in looking at the whole house, we remembered there is an odd-one-out in the loft. Checking it, it appears it has been dead for some indeterminate about of time.  So best to replace it too. It was installed in July 2002.

Our first impulse would be to get new Nest units, but, alas, Google decided to get out of the business and no longer makes Nest smoke detectors.  They seem to want to push us to a First Alert unit advertised as "Nest compatible", but the reviews of that on Amazon suggest it is not very well made.  Lots of "dead on arrival" and "won't work with our existing Nest units" reviews.  The Nest detectors seemed to be really well made.

So checking Consumer Reports, their best rated smoke and CO detectors are made by Kidde.  The specific model listed in Consumer Reports is no longer being made, but the successor unit seems to be the 30CUA10.  Amazon has these, for hardwired units, in two variants.  One that beeps and chirps, and another that beeps, chirps, and speaks.  Our experience with the Nest says that it is much better if the unit speaks.  It is better for it to say "Smoke" or "CO" than to make some beep or chirp that we have to decode.  If I can even hear them.  So we got three of the voice activated hardwired Kidde 30CUA10 models from Amazon.  $209.97 for the 3.

Again these will have to be replaced in 10 years, but we have two more Nest units (one in the utility room, one in the Living Room by the sliding door to the back porch; those will need to be replaced by 2031 at the latest.)

Let's start in the hallway.  In the corner, next to the computer room, we have a Nest.

 We can twist the Nest off and unplug the power supply to expose the mounting ring and socket.

 Loosening the mounting screws to remove the mounting ring, turning off circuit 35, and removing the electrical nuts gets us the bare wall and power lines.

 Reversing this, we can use the same electrical nuts to attach the new power supply plug and the same mounting screws to attach the new mounting plate.  Note the two blackened "A" on the mounting plate.  I used a magic marker to make them visible.  By putting them horizontal, the new detector should be straight up and down.

 which lets us plug the power supply adapter into the new Kidde detector, and then screwing it onto the new mounting plate, and we have a new smoke and carbon monoxide detector.

 

It turns out that the smoke detector in the Loft is also on circuit 35, so we do the same thing up there to install the second new unit.

 And our third new unit, on circuit 25, by the Master Bedroom, gets the same treatment.

 And, of course, we have to turn circuits 35 and 25 back on.

These new Kidde detectors are not as polished as the old Nest detectors.  They do have a voice but it is very limited ("Fire", "Warning: Carbon Monoxide").  Nothing like "this is a test, only a test.  It will be loud." They do not communicate.  They don't report status to an app.  Or send me monthly e-mails saying everything is working fine.  And yet, they aren't that much cheaper than the Nests were.