I am adding an outdoor floodlight and when I opened the motion sensor box for the existing lights, I found the neutral wire feeding the light was not connected in the box. I think this neutral should be connected with the other neutrals in the same box, but I wanted to make sure that is correct before rewiring it. When I checked the light fixture itself, there are several neutrals wired together in that box. Should I join the light neutral with the other neutrals in this box?

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Note: There were several other issues with this box also that I fixed (box not grounded, not outdoor rated box, no cable clamp etc.).

  • Without knowing anything about the circuit; beyond the one photo you've provided, it's difficult to say for sure what's going on here. Where do the black, white, and red wires leaving the box go? Where do the cables entering the box come from? – Tester101 May 16 '15 at 14:03
  • Cable is entering the box is from a wall switch, the cables hanging down are from the motion sensor and they feed carriage lights. So the black and neutral wires from the motion sensor are connected to the switch and the red wire is going to the carriage light. The neutral wire to the carriage light is the one not connected. – David L May 16 '15 at 14:58
  • If the neutral wire is not connected to anything, how is that the light is working? A light needs a minimum of TWO wires to operate and both wires must be connected. – Tyler Durden May 16 '15 at 15:23
  • There are other neutral wires connected in the carriage light box so I assume they are using that for the return path. – David L May 16 '15 at 15:38
  • It sounds like in this situation, you should not connect that wire to anything. It might help you understand why not, if you draw yourself a simple wiring diagram of the circuit. – Tester101 May 16 '15 at 18:21

I have seen two 14/2 cables used instead of a 14/3 cable. 14/2 is a hot (black), neutral(white) and a ground(bare copper), 14/3 is hot, neutral, and a load (red). It is used for three-way switches or smoke alarms where the third one is used to signal all alarms to sound when only one detects smoke.

I don't know what your setup is but it may be similar to the smoke alarms, which would mean that the neutral is not used. The original installer may not have had 14/3 for whatever reason.

  • It's a 300.3(B)/310.10(H) violation to parallel neutrals in that manner (or any other manner for that matter -- the conditions that do allow paralleling of conductors simply don't apply in residential work) – ThreePhaseEel May 16 '15 at 18:01

I agree with the other poster. A motion sensor needs only three wires. It looks like your box has four wires (we don't count grounds). So the extra wire is not needed. As he said many people have extra cables with 2 wires but not to many people have extra cable with 3 wires. So some people just use what they have (2 cables with 2 wires in your case). So the extra wire can just stay disconnected. If your lights and motion sensor are working, than the neutrals are all working properly.

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