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I am trying to install a motion activated light switch in my basement of my condo in the United States. On the switch it states that it's max load is 500 watts which should be plenty since the switch itself as far as I'm aware only controls 5 lights in my basement which are at max 60 watts combined.

The switch that I got has 4 wires, a red load a white neutral a green ground and a black hot wire. In the gang box of my basement, when I took the current switch out, this is what I saw:

photos.app.goo.gl/wS7buufAx4RHFQTH6

photos.app.goo.gl/BGx6gn7fdMcKgLFm9

In the above photos, you can see three separate groups of wires each with white insulation on the three groups of wires within the gang box. Within each of the three groups, there is one black wire, one white wire and one ground. The three white wires were not in use by the previous switch so they were all joined together and a wire nut was used. I saw that the three grounds from the three separate groups were all combined and connected to the bottom ground of the previous light switch. Two black wires were connected to one black wire clamp while one other black wire was connected to another black wire clamp.

I never came across something like this before but I attempted to connect the new switch to this wiring. Below is a picture of the new switch wiring I am trying to put in.

photos.app.goo.gl/kD5KHePEg6pRe93A7

When I took all the wires off of the old switch, I turned the circuit back on and I found that the entire circuit was not complete since I found that this one circuit energized my living room and basement, even though this switch only powers 5 lights in my basement. I was wondering, since there is a sump pump on the circuit (but not controlled by the light switch), would this light switch not be able to handle the sump pump kicking on?

Since I never came across a gang box like this before, I was wondering, it is possible to safely wire this new switch in? If so, how would I go about doing so? Thank you.

EDIT: Also, when I use a non-contact voltage tester, it appears as though only one black wire out of the three groups is hot when the circuit is flipped on.

Also, here is a link to the switch that I am trying to install https://www.amazon.com/dp/B0752W92LJ/?tag=stackoverfl08-20

  • Can you provide a make/model or instructions for the new switch? – ThreePhaseEel Apr 4 at 0:14
  • I hope you somehow kept track of which two black wires were connected to the same switch screw terminal. – A. I. Breveleri Apr 4 at 0:49
  • In your third photo, most of the switch is out of frame. If you can't post a better pic, or provide the switch make and model, then describe the wires attached to it and the labels on the wires. – A. I. Breveleri Apr 4 at 0:52
  • amazon.com/gp/product/B0752W92LJ/… is the link for the switch. And I did note where the two black wires that were connected to the same switch screw terminal. – Justin Todd Apr 4 at 0:53
  • Thanks for responding and adding pictures. Great question. – JPhi1618 Apr 4 at 3:34
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I see where you took the 2 blacks that had been on the same terminal of the old switch, and joined them with a wire nut. Good instincts.

Now, as you observed, the cables coming into the box had exactly the same color scheme- 1 black 1 white 1 bare. That is how cables are made. The colors indicate nothing about the purpose/function of the wire, however white must be used for neutral if neutral is present. So there's that. If you want color coding by function, you must re-mark the wires e.g. With colored tape. That is exactly what I want you to do.

Take the remaining solo wire and mark it with red electrical tape. I like red for switched-hot, and so does everyone else including your switch.

As it happens, the blacks and whites are color coded correctly (black=always-hot).

Now, they're color coded. Match 'em up EXCEPT STOP. DO NOT HOOK UP RED.

Now, see if the switch will power up. If it does, then shut off power again and hook up red; you're done.


Now, we are all assuming the usual situation, where supply comes in on one cable, and always-on power is carried onward down another cable. Given you have at least 5 lights here, it's possible that 2 strings of lights branch from the switch, and we have it all backwards. In that case, the solo black is supply, and the two blacks together are to-the-lamp and ought to be red. In that case, hooking the switch black to the solo black will make it power up. Then mark the other two blacks red and onward!

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This should be pretty straight forward. The two black wires that were connected to the same screw need to be connected to the black "line" wire of the switch (three wires together). One of the blacks is the power coming from the breaker (The one the non-contact sensor detected). The other black leads to the rest of the circuit. It doesn't matter what else is on the circuit (pump, lights, outlets, whatever).

The red "load" wire from the switch will go to the remaining black wire (that was alone on the other screw of the original switch) - this is the one that goes to the light.

The white neutral wire on the switch should be bundled with the other three whites. When bundling 4 wires, you probably need the next size up in wire nuts. The typical yellow/orange ones are often only rated for three wires max and that is important. I almost never use those orange ones that come with fixtures and switches because they are usually small and cheap feeling.

The green on the switch should be bundled with the bare copper wires similar to the whites.

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