Don't smoke the smoke detector....
May 10, 2011 1:51 PM   Subscribe

I need to get some smoke detectors but I am having trouble finding out what the right kind are. There are, as far as I can tell, three different kinds. Stand alone, interconnect and hard-wired. What do the plugs that hang from the ceiling look like for the interconnect and for the hardwired? What do I ask the guy at the hardware store for (Ace just said they are on the endcap and the detectors there had nothing that told me what type they were)?
posted by CodeMonkey to Home & Garden (5 answers total) 1 user marked this as a favorite
Maybe you could post a pic of the setup you now have? That might be helpful. My inclination (I am not an electrician, but have replaced some smoke detectors) is that, at one time (if you have wires hanging) there were interconnected smoke detectors. At some point in the house that string of wires is connected to an outlet (in my house, there is a smoke detector next to a light in the unfinished basement, there are a pair of wires running from that detector to an outlet on the side of the light fixture in the ceiling).

You could, of course, just install free standing, battery powered smoke detectors and ignore the wires that are there. If you're wanting interconnected (meaning if one goes off, they all go off, and that can be a lifesaver if there is a fire, and annoying as hell if the kitchen gets a bit smokey when you're cooking).

All that said, since this is a pretty critical thing, you might want to consider spending a few bucks and having an electrician come in and explain what you've got, once you know that, the replacement should be easy.
posted by tomswift at 2:45 PM on May 10, 2011

"interconnected" alarms can actually be found in both hard-wired and battery-only flavors nowadays, actually. the battery kind use radios to sync.

you'll really need to figure out what kind of alarms you have now. if you don't already have hard-wired interconnected alarms, for instance, and you want to have them be interconnected, you may have to have wire run. if you've just got battery-powered alarms now, you'll need to have your house wired for smoke alarms. that said, new hard-wired alarms will come with the necessary wires and harnesses you'll need to install them, so if you're comfortable with working on electrical stuff, you ought to be able to just pull the old ones out entirely - mounting bracket and all - and replace them with the new ones, assuming you have hard-wired ones already.

on the plus side, you can usually find manuals for new alarms online, so get the make and model for the alarms you're looking at and google them. you can usually download the manual, which will tell you how to install the alarms and what they actually do. you may be able to do this with your old alarms, too, so you can see what they supported or how they're wired up.

and, the easiest way to do this would be to just get battery-powered ones and install 'em, as tomswift noted. or, get an electrician to handle it.
posted by mrg at 3:41 PM on May 10, 2011

You may know this already but there are differences between smoke detectors in the way that they sense smoke.

Optical detectors catch fires which begin with a long period of smouldering.

Ionization detectors are cheaper and are what you generally get given in a hardware shop when you ask for 'a smoke detector'.

This is a useful source of information on the subject.

And here's the corresponding wikipedia article.
posted by southof40 at 4:45 PM on May 10, 2011

I just changed my smoke detectors, and they are interconnected hard-wired. Here's a few photos of mine, and an explanation of what you are looking at...

First, a few notes.
- If your house is wired for the smoke detector, then by all means consider those. The benefit is that the battery doesn't die just when you need it the most. If your house is not wired for the smoke detector, then the rest of my post really doesn't apply. But if you read along, you'll understand about the wires and what interconnected alarms do.

- Anyone can do this, and it takes about 10 minutes. I say this as someone who had no idea what I was looking at, and as someone who wasn't entirely sure that I even owned a screwdriver.... Oh, you'll need a screwdriver and a chair to stand on.

1. If it's wired, you need to turn off the electricity before starting. Find the switch in the fuse box and turn it off.

2. The thing you see on the ceiling is a cover that holds the alarm. Twist it hard and it comes off. Do that. After you do, it will look like this.

3. That plastic rectangle holds three wires. It connects the wires to the plastic thing you took off. Your new alarm comes with a new one. Pull on it hard to pull the wires out of it. Without the plastic rectangle, you can now pull off that shield so that you can see the hole that is cut into your ceiling. It looks like this. Here is a close-up of the wires.

4. Notice here that the wires are different colors: White, black, and yellow (the yellow one is sometimes red instead, but the white one and the black one will always be these colors). The black one is the hot wire. The white one is the neutral wire (the ground). The yellow (or red) one is the interconnect. This is important. Your new detector has wires, too, in the same colors. You will match black with black, white with white, and yellow (or red) with yellow (or red). If you don't have interconnected alarms, then you won't have a yellow (or red) wire, and you won't match the yellow (or red) wire on your alarm with anything at all.

5. Caps hold the wires together like here. The caps are plastic oblong (beige in my case) things that hold the wires really close together. Basically they twist on and off. Start with one of the colors, and untwist one of the caps. You'll notice that the colors were just a casing, surrounding many fine wires, which are exposed at the end.

6. With the new alarm, take the same color wire and hold it side-by-side with the wire from your ceiling (that is, all the little fine wires together). Then, twist the cap on really tight... as tight as you can with your fingers. You want it tight, because the two wires in there need to make a good connection. A loose connection works a lot like the electric burner on your stovetop -- and it'll get hot. So, very finger-tight.

7. Repeat steps 5 and 6 for the other color(s). If you are not interconnecting alarms, then just leave the red one on the alarm part as it is. It'll have a cover, so leave that cover on it.

8. Shove all the wires back in the hole and put in the new shield thing that hides the hole (the shield you pulled off in step 3). It has a plastic rectangle to connect the three wires (like you removed in step 3) to the alarm. You must push it very, very hard, but it will connect to the alarm.

9. Take the new alarm and remove the plastic around the emergency battery (the battery is powered on in case there is a power outage). Connect the battery in the alarm, and then twist the new alarm into the ceiling. You're done! Go back out to the fuse box and turn on the electricity.

For what it's worth, I got a Kidde brand alarm because they got good reviews in Consumer Reports magazine.
posted by Houstonian at 6:50 PM on May 10, 2011 [1 favorite]

Actually, I got step 3 a bit wrong. You don't have to remove the plastic rectangle. You just unscrew the shield and then pull the shield down. The old alarm will dangle in the air until you unscrew the caps, which releases the old alarm so that you can connect your home's wires to the wires in the new alarm.
posted by Houstonian at 7:40 PM on May 10, 2011

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