Smoke Alarm Interconnect Wire

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DBoone

DBoone

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Location
Mississippi
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General Contractor
Is the red interconnect wire on smoke alarms at 120v to ground when the alarms are activated?


I ask because a friend of mine runs 14-3 from panel to smoke to smoke to smoke, etc. Red wires are connected in all smoke alarm boxes and the red in the panel is usually rolled up with nothing covering the tip of copper on the end.


Just wondered if the wire was to touch the side of the panel would it make sparks fly.
 
He should be running 14-2 from the panel to the first smoke and 14-3 between smokes.

I don't know for sure, but I've always assumed the red wire was 120v when in alarm. I would make sure it's capped in panel. I would put a note on it so it doesn't accidentally get connected to a breaker later.
 
DBoone said:
Is the red interconnect wire on smoke alarms at 120v to ground when the alarms are activated?


I ask because a friend of mine runs 14-3 from panel to smoke to smoke to smoke, etc. Red wires are connected in all smoke alarm boxes and the red in the panel is usually rolled up with nothing covering the tip of copper on the end.


Just wondered if the wire was to touch the side of the panel would it make sparks fly.
Click to expand...

I found one source on line that said it carries 9 volts. A Kidde patent from 2004 suggests 12 volts DC.
 
Coppersmith said:
He should be running 14-2 from the panel to the first smoke and 14-3 between smokes.

I don't know for sure, but I've always assumed the red wire was 120v when in alarm. I would make sure it's capped in panel. I would put a note on it so it doesn't accidentally get connected to a breaker later.
Click to expand...
Not 120 volts, I know because I put 120 on that wire once and it destroyed the interconnect. The smokes still worked individually. Also unless some huge type of house I never ran a separate circuit just for the smokes.
 
Definitely 9VDC. The smoke alarms have to work on battery back-up during a power loss. I'm guessing it's +9 VDC out on the red in alarm condition and - 9 VDC on the white (although in DC the polarity in this case really doesn't matter).
 
goldstar said:
Definitely 9VDC. The smoke alarms have to work on battery back-up during a power loss. I'm guessing it's +9 VDC out on the red in alarm condition and - 9 VDC on the white (although in DC the polarity in this case really doesn't matter).
Click to expand...
I don't know how they work but was going to suggest that there is likely a signal on that line when running on batteries and there is an alarm condition.
 
kwired said:
I don't know how they work but was going to suggest that there is likely a signal on that line when running on batteries and there is an alarm condition.
Click to expand...

You could follow the patent link in post #3.
 
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