Red Wire in Smoke Detector Electric Box?

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Old 03-25-19, 07:26 PM
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Red Wire in Smoke Detector Electric Box?

Hi All,

I have hardwired interconnected smoke detectors, and they use black, white, and yellow wires (presumably for power [black/white] and interconnectedness [yellow]).

When I look up in the electrical box in the ceiling, there is also a red wire that is not used (instead it is wired together to the next red wire with a wire connector).

Any thoughts on what this red wire is for? I had read that four wires means that it is wired to a security alarm system so that the security alarm is notified of a fire. But we don't have a security system, and we've been here for 7+ years and have never noticed a security alarm panel.

Any thoughts on this red wire?

Thanks!
 
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Old 03-25-19, 08:08 PM
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Usually that red wire is used to interconnect smoke detectors. Basically that is where your yellow wire (some uses red) of smoke detector attaches to.

Weather it is also attached to security system is up to whoever installed the system.
 
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Old 03-25-19, 08:15 PM
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Thanks for the quick response.

Do you mean that you think the red wire (or the fact that there is a 4th wire, anyway) is for connection to a security system?

If so, which I guess is possible, I have no idea where it might be terminating! So I guess my next question is (which I know no one can answer) where is that security panel?!!

Thanks again!
 
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Old 03-25-19, 08:23 PM
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Does wiring in your smoke detector junction box have 4 wires excluding ground?

Usually, smoke detectors are connected to 14/3 cable, which has black, white, red, and ground wire.
This 14/3 cable runs between smoke detectors and you can use red wire for interconnecting.

If you have black, white, yellow, red and ground instead, you must have a conduit system. In that case, I would have no idea what the red wire is there for. You will have to open each smoke detector junction box and see what it is connected.
 
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Old 03-25-19, 09:18 PM
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A little confusion here.

The OP has a three wire cable w/ground. That's called a three wire cable.
Ground is not included in the count.
Black - power
White - neutral
Red - interconnect.
Your yellow wire from your smoke detector will go to the red wire.

Recommendations...... replace/install interconnected smoke/smoke CO detectors at the same time. Do not mix and match different smoke detectors from different companies or different ages.. Do not short the red to black or your smoke detectors will be ruined.
 
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Old 03-25-19, 09:54 PM
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Hi PJ,

Thanks for your response.

The black, white, and yellow wires are all connected into a harness. I think that's the right term; its basically this thing: BRK Electronics First Alert ADK-12 Adaptor plugs to replace a Kidde Smoke Alarm (pack of 12).

The wires in the electrical box in the ceiling are connected to the white end in that picture, and then the black end is plugged into the back of the smoke detectors.

When we moved into the house ~7 years ago, all I did was replace the smoke detectors - I didn't do any re-wiring. They are all Kidde, and Kidde has confirmed to me that all the ones I have are interconnectable together (both wired and wireless).

I'll check again when I have a chance to see if the yellow wire in the harness goes to the red wire in the electrical box, but I'm pretty sure the red wire was connected to another red wire.

thanks again.
 
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Old 03-25-19, 10:02 PM
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That adapter is meant for home owners without electrical skills so they can replace smoke detector without rewiring connector (harness) on to the house wiring.

Red or yellow wire should be connected to red wire of the cable unless you don't want them to be interconnected.
I have seen some installations interconnect wire was never connected and still had a factory cap on the red wire. Don't know if that was intended or the installer just didn't know what to do with it.
 
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Old 03-25-19, 10:07 PM
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Yes..... the red wire will be connected to another. It loops thru each box. That adapter is just converting from one brand to another. I'm not familiar with wireless smokes talking to wired smokes but all the wired smokes I install need to be connected to the red wire to talk to each other.
 
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Old 03-26-19, 08:43 AM
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Iambition - I thought one of the reasons for the harness was also quick/easy disconnect in case there was a problem with the detector. I don't see any downsides to using the harnesses, do you? (They were there when we purchased the house, and it never occurred to me to remove them...should I?)

PJ - Kidde has a pretty innovative product. Its hardwired/AC and its interconnect function works both ways. It connects (via wire) to the regular interconnect system. It also has a wireless "radio" (right term?) that communicates with Kidde's wireless alarms. That you, you can put a wireless alarm in an area where you don't have it hardwired, and all the alarms (wired and wireless) will work together. Basically, this product is a bridge between the wireless and wired systems.

I have 6 hardwired smoke or smoke/CO alarms, 1 of these innovative products, and 5 DC powered wireless smoke alarms. When 1 gets triggered, all 12 start going crazy! Great for if there was an actual fire; not so good at 5am when one of them decides it should be triggered for no reason, and I'm trying to locate which one to hush it. (Interesting fact: Kidde's regular alarm blinks quick red if it is triggered; Kidde's "special" alarms blink quick green if triggered - try remembering that at 4am when its crazy loud everywhere and you just want to shut it off!)

Anyway, that innovative product is Kidde's RF-SM-AC (sometimes referred to as RF-SM-ACDC: https://www.kidde.com/home-safety/en...ms/rf-sm-acdc/

Great little product.
 
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Old 03-26-19, 09:02 AM
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It looks like at some time in the past someone switched brands of detectors. That adapter is used to connect different brands together. As long as each hardwired detector is connected to the house wiring black & white (power) and red (signal) you should be good to go. If you buy new detectors you'll find they come with the newer style pigtail connector that has black, white and red stripped wires on one side and a plastic clipped plug on the other side to easily adapt from house wiring to the detector.
 
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Old 03-26-19, 09:21 AM
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Thanks for your note.

The item I linked to is not the exact item that's in our electrical boxes. Its just similar. (I tried to make that clear in my earlier post; apologies if it didn't come out that way.)

In fact, I needed to use this item to connect the harness in the electrical boxes to my detectors: https://www.amazon.com/gp/product/B0033PRWT6 If you look at the fourth picture there on the Amazon site, that looks to be the setup I have.

Thanks again.
 
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Old 03-26-19, 11:19 AM
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I thought one of the reasons for the harness was also quick/easy disconnect in case there was a problem with the detector.
Yes that is the purpose. However, what you linked was an adapter for harness.
Smoke detectors come with harness with connector on one side and just wire on the other side. You can connect this wire to house wiring in the junction box without purchasing any of those adapters. In my opinion, that is just waste of money. It is really meant for home owners who are scared of undoing wire nuts.

If you have wireless interconnect models, you don't need to connect interconnect wire. But, if there is one, I'd say it is best to hardwire them.
Wireless interconnects are needed for the houses that does not have separate smoke detector circuit. In older houses smoke detectors are often just tapped from nearby lighting circuit and thus don't have interconnect wires between smoke detectors.
 
 

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