Hard Wired Smoke Alarms - Odd Problem


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Old 01-23-08, 08:07 AM
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Hard Wired Smoke Alarms - Odd Problem

Hi all,

I'm looking for information on how hard-wired smoke alarms work in order to troubleshoot a problem I'm having.

There are 7 alarms in the house. I needed to replace the battery in one of them and upon plugging the electrical connector back in I got a POP! w/ a blue flash, some smoke and all of the alarms started sounding (or so I thought - more in a minute).

I went for the circuit breaker panel thinking (hoping) that the breaker had tripped with the obvious short that had just occurred. It had not. All the alarms were still sounding.

I removed each alarm from the electrical power and they were still sounding. I removed the batteries and obviously they stopped. Interestingly, only 4 of the remaining 6 were actually sounding. 2 were silent. I pushed the test button on them and they worked.

After a few minutes, I plugged one of them back in and it sounded again (but the two silent ones remained silent). I unhooked it and waited a bit longer. Eventually I was able to plug them all in (except for the obviously cooked one) and they're all quiet now. Each work individually but when I push the TEST button the others don't sound. I don't remember if they're supposed to all go off when you push the test button on a single unit but I'm pretty sure they are. I find this odd. Could they all be damaged? I can see a black mark on the red wire at each detector (even the silent ones).

The wiring is pretty simple, right? Hot, neutral and a wire that connects them to each other? Should I just replace them all (they're 9 years old anyway).

Thanks,
Jim
 
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Old 01-23-08, 08:12 AM
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They need to be replaced every ten years anyway. Go ahead and replace them.
 
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Old 01-23-08, 08:29 AM
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I agree with the recommendation to just replace them all as it's about time anyway. If you have gas or wood burning appliances in the house, get at least one combination smoke+carbon monoxide detector for each floor in the house. The rest of them can be just regular smoke detectors. I like the line of talking Kiddie detectors -- they have both smoke and combo detectors that interconnect.
 
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Old 01-23-08, 03:55 PM
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I would also consider having at least a couple of "smoke & fire" alarms, which use 2 different technologies.

You should be able to change the battery without taking down the detector.

My mistake: sometime ago, as a new homeowner, I assumed that the smoke detectors were powered up and working. When I decided to change the batteries, I realized that they were OFF! Three months with no smoke detectors, thatís a scary thought. So, I pulled them down and reconnected them, BUT, one of them had a black wire that was exposed! I was lucky I saw it before touching it. The lesson here is turn the power off when removing them.

Ironic how a smoke detector could possibly be a source of fire (and shock) if the wiring is wrong.
 
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Old 01-23-08, 04:22 PM
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I replaced all 7 with new ones. One was a combo smoke/carbon monoxide and the rest are smoke. Replacing them all fixed them all. It must have been some surge to bake them all at once. The burn mark was on the 9V communication line that connects them all. The 120V must have come across there somehow.

Thanks!

Jim
 
 

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