73 votes
Accepted

What on earth is this small wall-mounted computer?

It's a temperature sensor w/ wireless transmitter: https://www.inovonics.com/products/dual-input-temperature-transmitter-en1723/ I found that by googling the various numbers printed on the stickers -...
Nate S.'s user avatar
  • 6,382
58 votes
Accepted

How did a circuit that was shut off at the breaker almost kill me?

After writing out the question, I realized I had forgotten to check something. I went back to the panel to see if any other breakers besides the dryer circuit had flipped off, and sure enough, the &...
Kevin's user avatar
  • 1,457
49 votes
Accepted

CO detector starts beeping every morning at 6am

If your CO detector were actually detecting CO, it would not chirp. It would sound a continuous, and very, VERY loud alarm you would definitely recognize. The chirping is a universal (as far as I ...
The Evil Greebo's user avatar
39 votes
Accepted

I found this white electronic device on my ceiling. What is it?

To me, it appears to be a First Alert AC10-500 smoke/CO alarm Manufacturer link P.S. First Alert may manufacture other alarms with a similar shape
Telescope2334's user avatar
36 votes

How did a circuit that was shut off at the breaker almost kill me?

Could be an unmarked Multi-Wire Branch Circuit We often look at people's panels for other reasons, and we often say "hey, see the red+black wires from the same cable, going to 2 independent ...
Harper - Reinstate Monica's user avatar
30 votes

CO detector starts beeping every morning at 6am

It's normal for gas and smoke detector batteries to indicate impending failure during the coolest part of the day. The chemical reaction that produces the electrical current is reduced by low ...
isherwood's user avatar
  • 138k
28 votes
Accepted

FirstAlert smoke detector low battery warning continues after opening battery drawer and replacing batteries

The problem was that, when I initially removed the old batteries, I damaged one of the terminals within the battery drawer. All the terminals are thin metal plates that deform easily; there are no ...
Reign of Error's user avatar
22 votes
Accepted

Why should we replace smoke alarms every 10 years?

It likely has to do with the lifetime of the hardware itself. Remember, there's a circuit board and a light source, as well as a detector. Those don't last forever. So the manufacturer certifies the ...
Machavity's user avatar
  • 24.9k
18 votes
Accepted

What do I do with the ground wire in a smoke detector install?

That looks like a plastic box to me. If it is metal, code requires that the box be grounded. If all the external parts of the smoke detector are plastic then a ground is not required (the same is true ...
Ed Beal's user avatar
  • 103k
17 votes

Are rechargeable 9-volt batteries suitable for use in smoke detectors?

I was advised by one of the big smoke detector manufacturers that the real issue is voltage. Most battery-operated items will still run, more or less, on a much lower voltage than the nominal voltage ...
fixer1234's user avatar
  • 6,118
15 votes
Accepted

Is this smoke detector safely connected?

This is a Firex 4618, interconnected smoke alarm with backup battery. Here is the manual which explains Green Light means its operating on A/C (hardwired) power. Otherwise, its running off the backup ...
freshop's user avatar
  • 1,876
15 votes
Accepted

Should lintels above wall portals be considered for smoke alarm placement?

Yes and fantastic question, the lintel/header/apron will absolutely delay detection...by quite a lot. Therefore, I absolutely agree with Jack that you need to place the detector closer (the lintel ...
Iggy's user avatar
  • 10.3k
15 votes

What is this electrical fixture above a natural gas fired forced air furnace?

That looks like it was part of a whole house smoke detector system. Smoke detectors do have a limited life and when they start failing folks just pull them out. Since the detector was close to the ...
Ed Beal's user avatar
  • 103k
14 votes
Accepted

What should I do about this smoke detector that beeps constantly?

Doesn't look like it has a battery. How old is it? There should be a manufacture or expiry date written on the cover. Many older AC powered detectors didn't have backup batteries. That cable you ...
Grant's user avatar
  • 5,659
11 votes

Should a smoke alarm be installed in the attic?

As a firefighter that recently battled a large and rapidly moving fire that appears to have started in the attic, I found myself searching the topic of smoke alarms in attics. Though it is a low ...
user67462's user avatar
  • 111
11 votes

Why should we replace smoke alarms every 10 years?

Smoke alarms come in two categories (sometimes combined). Photoelectric and ionization. The lifetime is directly related to the technologies and the environment. The technology limitation of the ...
Mike's user avatar
  • 111
11 votes

Why should we replace smoke alarms every 10 years?

Highly condensed version: studies have shown that the electronics within the detectors fail at a rate of 3% per year. The 10 year mark was chosen based on the cumulative fail rate being over 25%. ...
Mad Myche's user avatar
  • 211
11 votes

Are rechargeable 9-volt batteries suitable for use in smoke detectors?

You should use only the batteries recommended by the manufacturer of the detector, and all of the hard-wire w/battery backup models I have experience with expressly forbid the use of rechargeable ...
Jimmy Fix-it's user avatar
  • 35.8k
10 votes

CO detector starts beeping every morning at 6am

A low battery is the most common cause of seemingly-random chirps in smoke and CO detectors. Detector end of life is probably the second most common cause. How old is the CO detector? Their lifetime ...
mmathis's user avatar
  • 8,862
9 votes

Should a smoke alarm be installed in the attic?

We specify a "heat detector" in the attic and crawl spaces of all our homes. A "smoke detector" will pick up a neighbor's burn barrel smoke (products of combustion) but a heat detector operates on the ...
Lee Sam's user avatar
  • 23.2k
9 votes

Should lintels above wall portals be considered for smoke alarm placement?

The Code (See ICC R314) requires a smoke alarm located: In each sleeping room. Outside each sleeping room area in the immediate vicinity of the bedrooms. On each additional story, including a ...
Lee Sam's user avatar
  • 23.2k
8 votes

Help with smoke detectors?

This detector housing is fairly generic - I've seen a few brands that all use very similar designs (probably all manufactured by the same company). As discussed in the comments, the ones I know of are ...
Moshe Katz's user avatar
  • 2,696
7 votes

What is this electrical fixture above a natural gas fired forced air furnace?

I have 4 First Alert smoke and CO detectors in my home that are all interconnected and are model SC9120B. The orange wire does the connecting. The sockets look exactly like the one in your photo. They ...
d.george's user avatar
  • 12.4k
6 votes

Nuisance smoke alarms

Some battery-operated alarms use a radio signal to interconnect so they're all set off together. You should be able to verify/test this using the test button: press it on one, and if the others go off ...
gregmac's user avatar
  • 29.1k
6 votes

Should a smoke alarm be installed in the attic?

I service thousands of smoke detectors every year and they should NEVER be installed in an attic. There are reasons code does not require them in attics but code is a MINIMUM requirement. If you want ...
Zubinell's user avatar
6 votes
Accepted

Why is a smoke alarm chirping at specific times of the day?

I have noticed this same phenomenon before, and the only explanation I can think of is that early morning hours are typically the coldest hours of the day in a house. Smoke alarms operate with a ...
PhilippNagel's user avatar
  • 4,957
6 votes

Do I really need Carbon monoxide detector

Yes, you need a CO detector. This is cheap insurance against an odorless gas that will kill you. Where I live, it’s a code requirement. Also where I live, you can get one for $30, and it lasts 10 ...
Aloysius Defenestrate's user avatar
6 votes

Help with smoke detectors?

As noted in the comments, these are almost certainly well outside their 10 year lifespan. Pull them down by whatever means necessary (they’re just plastic, so the mounting points will break if needed),...
Aloysius Defenestrate's user avatar
5 votes
Accepted

Can I mount a smoke alarm using magnets?

Smoke detectors should not be mounted within 12" of the corner of the wall. The air movement in the corner is practically nil thus rendering the detector useless. It needs air movement through the ...
ArchonOSX's user avatar
  • 19.8k
5 votes
Accepted

How can I open this smoke detector to change the battery?

It appears to have a hinge on one side and a locking tab opposite. Press it in the direction of the arrow until it moves, then swing the cover downward. Manual
isherwood's user avatar
  • 138k

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