How do I wire a smoke alarm off a light fixture?

Posted by bentley on March 28, 2009, 2:55 pm

Anyone know of a dual sensor, hardwired, & interconnected (wireless) smoke
alarm?

Which sensor type is more likely to go off for nuisance alarms: the ion or
photo sensor type?

A main consideration is how to hardwire one of these if all you already have
is a hardwired ceiling mounted light fixture right next to where you want to
mount the smoke alarm, but nothing else - that is, not yet anyway. I am no
pro contractor, but I could do it myself no problem. What do you need to do
wrt making it look and function as legal and safe (as need be) by running
directly off a nearby light fixture (with it's in ceiling wires)? String a
wire, under the ceiling drywall or over, need to cut a oct box into the
ceiling, hard-shield the wires, etc., what?

I bought a Kidde Pi9000CA dual sensor smoke alarm (ion & photo) that runs on
a (std. alkaline) 9V battery only. It has HUSH and TEST buttons. I am not
too concerned about not having either the interconnected (wireless) feature
or the hardwired features simply because you cannot get it with both of
these features at the same time; either is a bonus, but both is the only way
to go.

Posted by Phil-In-Mich. on March 28, 2009, 3:24 pm

> A main consideration is how to hardwire one of these if all you already
> have
> is a hardwired ceiling mounted light fixture right next to where you want
> to mount the smoke alarm, but nothing else - that is, not yet anyway. I
> am no pro contractor, but I could do it myself no problem. What do you
> need to do wrt making it look and function as legal and safe (as need be)
> by running directly off a nearby light fixture (with it's in ceiling
> wires)? String a wire, under the ceiling drywall or over, need to cut a
> oct box into the ceiling, hard-shield the wires, etc., what?

Most likely you will be missing a constant-on Hot wire in that ceiling
fixture box.

The switch for the overhead light fixture will interrupt the power on the
black wire.

I could be wrong, so test the wires in the ceiling fixture box first before
anything else. Also you could luck out and have 3 conductors plus ground in
cable going from switch to fixture box.

Posted by Nate Nagel on March 28, 2009, 3:33 pm

Phil-In-Mich. wrote:

>> A main consideration is how to hardwire one of these if all you
>> already have
>> is a hardwired ceiling mounted light fixture right next to where you
>> want to mount the smoke alarm, but nothing else - that is, not yet
>> anyway. I am no pro contractor, but I could do it myself no problem.
>> What do you need to do wrt making it look and function as legal and
>> safe (as need be) by running directly off a nearby light fixture (with
>> it's in ceiling wires)? String a wire, under the ceiling drywall or
>> over, need to cut a oct box into the ceiling, hard-shield the wires,
>> etc., what?

>
> Most likely you will be missing a constant-on Hot wire in that ceiling
> fixture box.
>
> The switch for the overhead light fixture will interrupt the power on
> the black wire.
>
> I could be wrong, so test the wires in the ceiling fixture box first
> before anything else. Also you could luck out and have 3 conductors
> plus ground in cable going from switch to fixture box.
>

Or a switch-leg configuration. That would work too.

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

Posted by Cwatters on March 28, 2009, 4:44 pm

> Anyone know of a dual sensor, hardwired, & interconnected (wireless) smoke
> alarm?
> Which sensor type is more likely to go off for nuisance alarms: the ion or
> photo sensor type?
> A main consideration is how to hardwire one of these if all you already
> have is a hardwired ceiling mounted light fixture right next to where you
> want to mount the smoke alarm, but nothing else - that is, not yet anyway.
> I am no pro contractor, but I could do it myself no problem. What do you
> need to do wrt making it look and function as legal and safe (as need be)
> by running directly off a nearby light fixture (with it's in ceiling
> wires)? String a wire, under the ceiling drywall or over, need to cut a
> oct box into the ceiling, hard-shield the wires, etc., what?
> I bought a Kidde Pi9000CA dual sensor smoke alarm (ion & photo) that runs
> on a (std. alkaline) 9V battery only. It has HUSH and TEST buttons. I am
> not too concerned about not having either the interconnected (wireless)
> feature or the hardwired features simply because you cannot get it with
> both of these features at the same time; either is a bonus, but both is
> the only way to go.

I imagine it depends which country you live in.

It's very easy in my country.

Posted by jloomis on March 28, 2009, 9:00 pm

Switch leg is running to the light......or......a hot is running to the
light......with a wire going to the switch to turn it on or off.......
The best scenario is a hot at the light fixture.....You have to test the
wire at the light fixture and see if it is hot all the time making sure it
is not the switch leg.
A smoke alarm needs to be always on and not switched......
So, if you can identify the hot lead you are in business.
jloomis

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