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NateHanson 11-07-2007 04:05 PM

Hardwired Smoke Detector question
Our 14 yearold house has a 120V smoke detector on each floor (1,2,3) but they are old, yellow, and not working.

I'm going to replace them, but I have some questions on how these work.

I'm assuming they're wired on the same circuit, although there is no dedicated circuit labeled in the panel. Could they be wired on the lighting circuit?

Hardwired Smoke detectors all sound simultaneously if one is triggered, right? That's my primary reason for wanting to update these, rather than relying on the battery detectors I've installed.

Any recommendations on which brand or model to buy for replacements?

Andy in ATL 11-07-2007 04:17 PM

They do not have to be on a dedicated circuit.. I often wire them on a dedicated circuit for the simple fact that it gives you an extra homerun in all the floors of the house. I'm in GA, which as of last year didn't require smokes in bedrooms, so as far as I was concerned it was a free homeun in case of an add on (they draw virtually no amps.). As for how they are wired... TYPICALLY a 14/2 (the "feed") goes to the first smoke. From there, a 14/3 goes from smoke to smoke with the black providing the juice, the white neutral, and the red conecting them all together. I recall in '02 a whole mess of bad smokes, but I can't recall the brandname... Haven't had problems since no matter the brand.

Shut the circuit off Nate, but then again you knew that.

Sammy 11-07-2007 04:58 PM

Good idea to replace them once they are up and working. Most mfg's suggest it every ten years or so.

They dont have to be on dedicated circuit, just all on the same one.

NateHanson 11-07-2007 06:09 PM


Originally Posted by Andy in ATL (Post 72339)

Shut the circuit off Nate, but then again you knew that.

But then how am I gonna know when I light my hair on fire? :huh:

Andy in ATL 11-07-2007 06:17 PM


Every good electrician knows never to smoke anything while looking up at a disassembled smoke detector on a dead circuit. The ash can easily ignite hair resulting in a "hair fire" which the smokie won't be able to detect. No detection= no knowledge of hair fire. BAD BAD BAD:yes: :whistling2:

frenchelectrican 11-07-2007 06:50 PM


Let me add few more comments related to the smoke alarms most 120 v interconneted smoke alarm useally are tied to one of the lighting circuits something like hallway light or simuair idea.

if you yank the smoke alarm down you will see the attachemnt plug in the back you should able noted there is 3 wires typically black red and white the black and white is for power but the red is for interconneting other smoke alarm [ just want to give you a head up make sure you have same brand run thru this circuit ]

some i will say some not all will use the same common plug in. in the back of smoke alarm so IMO really anytime you change it will be wise idea to check the rest of it.

i think someone did mention here if over 10 year old it is good time to replace it.

Merci, Marc

Andy in ATL 11-07-2007 07:03 PM

One more thing from me Nate that I forgot....No mixing brands or model numbers. They scream bloody murder when mixed.:yes:

NateHanson 11-07-2007 08:43 PM

Thanks for the tips guys. :)

Frenchy, are you saying that the mounting plates are usually the same for these? So I could get new units and they'd just plug right into the existing ceiling plates? That'd be nice.
Would it be a good idea to add one in the basement? It's got our mechanicals down there, and a non-interconnected alarm would never wake us up from way down there. If there isn't a reason not to, I'll try to run a 14-3 down there from the first floor detector.

That'll put a detector in the hallway on each floor, and the basement. Bedrooms each have 12V solo detectors. Does that sound like good coverage, or while I'm at it should I hardwire detectors in each bedroom too? (Wouldn't be too hard because the floors are all 2x4 truss-beams, but then, I'm not lacking for projects.)

Actually, while I'm thinking about this project, how much more expensive is it to install detectors that can be tied into a dialing box, or something like that to provide notification to me or to the FD? We're out here in the sticks, and nobody would know this house is on fire until we got back home. Neighbors are too far away to notice. So I figure a fire while we're away would burn to the ground. If it could be done cost effectively, I'd love to have some sort of automatic alarm system.

frenchelectrican 11-07-2007 11:34 PM


I am glad you asked me this question about the smoke alarm with the interchangable.

if that smoke alarm is simuair brand name like BRK , Kiddie, First Alert, i think few others as well.

but most of them been around for quite a while and i think it pretty much the same arrangement for a while but IMO you may end up replaceing the new pig tail on this all the smokies do have new pigtail the reason why i will explain in a sec becaues over the time that connector can loose the reation [ sp ][holding ] on the plug itself over the time few time i did took off and some actally just came apart.

humm now you mention you live in the "boonies " if i get this word right you are in deep country area so i dont know if any smoke alarm have the option of " ringing " to the Fire dept.

but i may try this idea but it up to you what you think what about the all in one burgur alarm they have a interconnecting for Smoke alarm too but myself i dont have much idea with it it was been a quite a while to see this kind of arrangement with this matter.

if you are instering to find out let me know then next day i will dig up more deeper info on this

Merci , Marc

NateHanson 11-07-2007 11:45 PM

We're on the edge of a small town, so there's a staffed fire department 5 minutes away. So fire coverage is actually pretty good, but unless I'm here to watch it catch fire, I'm afraid the response time would be far slower due to nobody noticing the blaze until it started working it's way through the forest to one of the neighbors' houses. :)

Burglar alarm type system would be fine, but that starts to sound expensive. And frankly we have no concerns about being "burgled". We don't usually lock the doors when we go away for a couple days.

Sammy 11-08-2007 06:28 AM

A monitored alarm would require more equiptment and a monthly fee...

You could possibly just attach an outdoor strobe/siren with little extra work that would at least make some light and noise outside if you think that would help attract attention.

Thats how my wife always lets me know dinner is about ready.... Smokes in the kitchen go off and I know its time to come inside.

RippySkippy 11-08-2007 07:44 AM


Originally Posted by Andy in ATL (Post 72339)
They do not have to be on a dedicated circuit.. I often wire them on a dedicated circuit for the simple fact that it gives you an extra homerun in all the floors of the house. I'm in GA, which as of last year didn't require smokes in bedrooms...

Wow...regional differences crazy! I live in central Iowa, and new residentials must have:
-- hard wired smoke alarms on dedicated circuit, and
-- one in each bedroom located at the highest point of the room, and
-- one above any lower level stairs, and
-- one located in a hallway shared by multiple bedrooms, and
-- one in the furnace/utility room

Bottom line if you live in an area that has building inspectors, new or remodel work, it's best if you call and ask about local requirements.

NateHanson 11-08-2007 01:03 PM

I found some digital dialers online that can monitor 2 to 8 inputs (fire, burglar, temp, water, etc), and call up to 4 numbers with a recorded voice message if any of those alarms are going off. A 2 channel dialer (all I'd need) costs less than $100. I'll have to figure out if these are simply connected to the red communication wire of the smoke circuit. If so this would really be a simple add-on, and I could have it call my cell phone, and the FD.

I'm going to consider this. I think it would be more effective and cheaper than a siren/strobe. Our neighbors may or may not hear a siren (it would have to be pretty loud, and then, only if they're home/awake). A strobe would not be seen by anyone but the chickens.

tyler101 11-10-2007 05:10 PM

An interesting read:

Sammy 11-10-2007 05:32 PM

Good info..

Bout an hour ago I finished up putting a hard wired detector in the laundry room that will later be hooked up to some others to be installed later.

They dont cost that much..

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