[jessechenven]

My basic problem is that when I roughed in the wiring for the circuit that powers my smoke detectors, somehow I managed to use 14/2 between two of the boxes. Everything else was on 14/3 so I could inter-connect the alarms. Now, the last two aren't connected. So, I thought, why not use the ground wire as the interconnection wire. Of course this leaves me without a ground on the last two detectors on the circuit. So, since the last detector is right near a switch for another circuit, I was thinking I could easily fish a wire to act as ground and connect it to the ground of the other circuit,
My questions:
-any problem with using the bare ground from the 14/2, as the interconnect wire between alarms?
-and, any problem with having hot and nuetral supplied by one circuit, while I borrow ground from the other.
FYI: All the boxes are plastic.

Thanks

[tkrussell]

You will not care for my answer,even though the bare wire is insulated inside the cable's sheathing, it cannot be used for the neutral, because a neutral is considered as being a current carrying conductor.

Nor can the neutral of another circuit be used for another circuit because of possible overloading the neutral with current from two circuits.

My opinion is that the load of the smoke detectors is so minimal, if you must do a short cut, the latter would be safer.

I really must insist that you try as hard as possible to snake in the correct cable to the smoke detectors, as once you use a shortcut, it will always be something you wonder about , and can cause problems.

However, if I were hired to do your wiring, and I made the mistake, I would be hiring someone to remove any sheetrock I needed removed to pull in the correct cable, to allow me to sleep every night.

Was this work permitted and inspected? Ask the inspector his/her opinion of how to correct this situation.

[mz2richard]

Hello! I must definitely agree with tkrussell in that you should absolutely do all that is necessary to change your 14-2 to a 14-3, even if it means ripping down some sheetrock, a small price for a sound mind. Remember, Safety First!

[jessechenven]

Okay... I can understand the reason for doing everything right.. but...

-I don't plan on using the bare ground wire as a neutral. I was going to use the bare wire as the interconnect between the alarms which signals them all to go off if one goes off. If I am not mistaken this interconnect doesn't carry full 120 voltage, but less, like you would have on a door bell, etc.

-I wasn't planning onn sharing a neutral with another circuit, but sharing a ground. So, my question is: Is it bad to have something with hot and nuetral from one circuit, but protected from the ground of another? Can you over load the ground?

Thanks for all your time.
Jesse

[tkrussell]

The third wire on interconnectable smoke detectors, red, will carry 120 volts to all the other smoke detectors. Each smoke gets a 3 wire Romex cable with black, white, and red, along with the bare ground ,which is understood and not counted in the cable.

The first smoke get a 120 volt two wire feed, and from the first smoke in line to the next and all other smokes get the 3 wire cable. The 120 volt is fed to each smoke by the black and white wires, the red is a switched leg, that will become energized when one smoke detector detects smoke and alarms, sending 120 volt back out on the red to all the other smoke detectors, causing all the others into alarm.

Since all the boxes are plastic and the cable is Romex, the smoke detectors are all plastic and do not need an equipment ground wire, which is the bare wire in Romex.

So each smoke detector and box gets a bare wire, but notice there is no place for it, all that is needed to be done is splice together and roll up in the box.

That does not mean to say the bare can be used for other purposes, it is intended as a ground, and must only be used as a ground.

So since the smokes and their boxes do not need a ground, no reason to try to get to another circuit for the ground. Just so it is clear, any and all together can and must be connected together, no matter how many circuit are in a box.

So from this point, I am confused with what you really need, if you have a 2 wire cable, black, white, and bare at two smokes, there is no way to send a signal out from these two smokes to alarm all the other smokes, unless you have a third wire, insulated.

If this does not clear this issue up, please get back with more details and questions.

[dclynch]

What about trying wireless interconnect? I think Consumer Reports rated smoke alarms recently and said the wireless variety worked well. If it is cheaper to buy new alarms than to rewire correctly, this might be a better choice.

[jessechenven]

Thanks for the idea, I'll check it out.

[Stratmando]

If you cannot replace 3 conductor for the 2 conductor. Safest choice would be the wireless
Interconnected smokes. You would need three. One each for the 2 on the 2 conductor.
Then you would need one on one of the 3 wire smokes, pehaps one closest to the two.
They are about $50 to $60 each.
Grounds inside the plastic box should be made up to maintain integrity, even though there is no place in box or on smoke.
Been a while, some interconnects, I forget the exact, but might be 120 volt interconnect
Uses Orange, and Yellow uses 9 volts? Or vice versa.