What is this thing on my smoke alarm?

There's a metal box attached to the side of my smoke alarm box with what looks like a phone line coming out of it. It travels between the joists for about 10' before disappearing into the subfloor above. I'd like to disconnect this box to mount the smoke detector in a new place (and will reattach then if needed).
PIc is at:
http://img89.imageshack.us/img89/8822/img0693st8.jpg
Thanks!
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Ok, let me try again with the pic: [url=http:// www.freeimagehosting.net/]
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On Jan 25, 6:00 pm, snipped-for-privacy@gmail.com wrote:

That is a 12V or 24V transformer supplying electricity to the furnace thermostat system, or to your doorbell, or perhaps an alarm system.
Dave
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wrote:

Agreed, that is a door bell type of transformer to supply low voltage to something. It really should be accessible, not hidden behind drywall. That looks like a bad shoddy installation job -- great photography, I can see a number of problems: There shouldn't be two cables under that one clamp, that 3 wire cable looks like it is attached to the joist with a wire staple or bent nail instead of an approved cable staple or strap, the curled wire seems to be spliced to another type where it changes direction, looks like scraps put together. I wonder what else is hidden behind that drywall.
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EXT posted for all of us...

If if it's approved for what's under it?

Looks like an Arrow staple to me.

Looks like it disappears where one can't tell where it goes. Nice to leave the long wire curled like that.
--
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snipped-for-privacy@gmail.com wrote:

It's a transformer to step down the 110 volt line to 9 or 12 volts for use in the smoke detector. The wire coming off it goes to some other low voltage device, probably another smoke detector or possibly a doorbell.
It's not attached to the side of your smoke detector. It's attached to the side of a junction box which your smoke detector is mounted to. If you remove the smoke detector from the J box you should see one of the 110 lines (two wires) connected to the transformer and two wires coming from the transformer to the smoke detector. Be sure to flip the breaker for this circuit before digging around inside the J box and hook everything up as before once you move it. If the coil of wire is not long enough to reach the new location you can safely splice an extra length of the same gauge wire and tape the splices well with electricians tape.
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Not sure but looks like, from that one picture, that it is a mains operated smoke alarm. With possibly a mains to low voltage transformer mounted on the side of the same electrical octagon box on which the smoke alarm is mounted?
The springy telephone type cord looks like it comes off the low voltage output of that transformer; whether it has anything to do with the smoke alarm itself is hard to determine!
Maybe it was merely a convenient means to obtain and convey low AC voltage to something else; such as a door bell/chime circuit? Or a home buzzer system or even some low voltage thermostats????
Or perhaps it is even a home brew alteration to the smoke alarm to transmit a signal or voltage to shut off or to alarm something else.
Needs someone with a knowledge of circuitry to trace out what is going on; virtually impossible to be sure of anything without hands-on.
If not electrically competent suggest don't do anything; AC operated alarms are sometimes linked between floors and are required to be so by insurance companies and fire inspection jurisdictions. Moving or changing one might (unsafely) disable a whole system.
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terry wrote:

You're might be more on the money than I am. I wasn't aware that smoke detectors are made to be connected to 110 volts. In any case, flip the breaker off and hook up everything as before.
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Some smoke alarms are AC operated. In fact starting some 30 years ago the (Public) Housing Corp. here required them to be not battery operated; too many cases of people taking out or not replacing the batteries!
Also new regs. require them, in many parts of Canada, to be linked between floors. Not sure if the AC ones have a storage battery inside to ensure continued operation in case the power fails or trips off (perhaps as the result of a fire!) but think not.
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You can buy them in whatever flavor you want or need. 9V battery, 120V, 9V&120V, interconnected or not, etc,etc.
wrote:

Some smoke alarms are AC operated. In fact starting some 30 years ago the (Public) Housing Corp. here required them to be not battery operated; too many cases of people taking out or not replacing the batteries!
Also new regs. require them, in many parts of Canada, to be linked between floors. Not sure if the AC ones have a storage battery inside to ensure continued operation in case the power fails or trips off (perhaps as the result of a fire!) but think not.
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terry wrote:

The 115 Volt AC type of smoke detector are manufactured both with and without a backup battery compartment. Were detectors are required to meet code the regulations often, but not always, require the kind with back up battery. I would be willing to bet that the transformer has nothing to do with the smoke detector unless it is a field designed circuit. Does the home have any kind of alarm system? Do you know were the alarm system gets it's power? If it is a field designed signaling circuit then one side of the transformers primary winding will be connected to the white wire and one side will be connected to the alarm common which will be the red conductor of the three wire cable. If it is smoke detector power supervision then when you open the breaker it will cause some signal in your home alarm system to be transmitted to the monitoring station and they will call you to ask if everything is all right. That last I would think extremely unlikely to be the case. The easiest way to find out is to disconnect one lead from the transformers external screw terminals. Then check to see if your door bell, furnace controls, or other low voltage devices if any still work. I'd bet even money on the door bell and give two to one odds on it having nothing to do with the smoke detector at all. -- Tom Horne
"This alternating current stuff is just a fad. It is much too dangerous for general use." Thomas Alva Edison
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Tom Horne wrote:

. The 2008 NEC, under AFCIs (210.12-B), has a fine print note referring to NFPA 72, the standard for smoke alarms. IIRC the discussion for the 2008 code change on AFCIs was that NFPA 72 requires a "secondary power supply" for smoke alarms on AFCI circuits. AFCIs in the 2008 NEC are required just about everywhere in a residence a GFCI is not required. (It would help if the FPN was more explicit.)
--
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wrote:

Here in Ontario, Canada line voltage smoke alarms have been mandated for new construction for the past 25 years, one is needed on each floor, a 3 wire cable hooks them together so if one goes off, they all sound off.
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The OP wrote:

Looks like a doorbell x-former. The 3 conductor romex is going to the other smokes for power and (red) interconnect.
--

-G

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Thanks everyone - you've got me believing it's my doorbell xformer. All the smoke detectors in the house ARE interconnected on a single circuit on 110V with battery backups in each. I do have an alarm system, so I was kind of suspecting that it might be related to that, hence my confusion. Also - this pic is in the basement where I'm putting up new drywall, so this was all exposed before, just nailed to a joist at the bottom of the steps. I actually have a much better place to connect the x-former to 110v power so I'll have access to it as this smoke detector box will definitely be behind drywall. But I'll check it tomorrow - I'm sure it is the doorbell. Last question - will I have any issues disconnecting the transformer from this box and moving it to another one? It's not integral to the j-box or anything is it (I only ask since I don't see mounting screws or anything).
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It's either got a locknut or a binding screw inside the box. When you open it, it'll be apparent. Move it anywhere that's accessible

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snipped-for-privacy@gmail.com wrote:

Sure looks like a doorbell transformer to me. You could always disconnect it and see if your doorbell suddenly stops working.
I suspect that you have a "tandem" type 120VAC smoke detector based on the 14/3 leaving that box. Generally the red wire is used as a tandem connection between the smokes so if one alarms they all start sounding.
nate
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That's exactly what it is. A plain Jane doorbell transformer. Just disconnect the low voltage wires and check your doorbell
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On Jan 25, 6:00 pm, snipped-for-privacy@gmail.com wrote:

Gawd only knows, from a picture, but it is remotely possible that the transformer is part of some enhanced alarm system -- possibly powering a bell or strobe that activates when/if the smoke detector goes off. Something like that would be used if the previous owner had a handicap.
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