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In my garage I have two lighting circuits with two separate switches in the same junction box.

Total, on both switched circuits, I have 16 recessed lights, each is a 15w LED. One switch is an occupancy sensor and turns on 6 of them. The other switch turns on the remaining 10.

The idea is that sufficient lighting turns on automatically when I enter the garage. But if I'm working on some project I want more lights so I turn on the second switch for full lighting.

You can imagine if I'm working under a car or something that the occupancy light will turn off (and I flail around to activate it again). What I want is for the second switch to turn on all the lights, even if the occupancy isn't triggered.

How can I wire this?

I have one line to the junction box. The box has two switches and two load wires. One load with 6 cans, the other with 10 cans.

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  • What kind of lights? (Total wattage).
    – Ed Beal
    Commented Sep 21, 2020 at 5:49
  • I would use the switch to control 2 relays, one for each circuit.
    – Solar Mike
    Commented Sep 21, 2020 at 12:15
  • Why not just use an occupancy switch with a positive-on override? Turn it on when you're planning on being in there for a while.
    – isherwood
    Commented Sep 21, 2020 at 13:13
  • @Solar Mike, can you provide an example?
    – Matthew
    Commented Sep 21, 2020 at 15:42
  • You describe this as two circuits but I don't think you actually mean two circuits as in fed by two different circuit breakers. You just have the lights divided up onto two switches, one which happens to be a motion switch, right? So the question is really...how can I have one switch turn on half the lights and one turn on all the lights?
    – Ben Franske
    Commented Sep 21, 2020 at 15:50

2 Answers 2

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The easiest way is to replace the manual switch with a double-pole switch, such as this example. This allows you to switch two independent circuits with the same switch. Connect the original switch connections to one pole of the switch. connect the other switch pole in parallel with the motion detector (extend the wires connecting to hot and switched-hot at the motion detector to connect to the other switch pole). If the motion detector has built-in wires, you can add the new wires to the existing wirenuts. If the MD has screw terminals, it would be best to add pigtails (short wires) from the MD to new wirenuts and then to the existing and new wires.

If you are unsure which terminals are which on the double-pole switch, try connecting just in place of the old switch. Once you have that working ysing two terminals of the switch, use the other two terminals to for the MD connection.

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  • Connecting a switch in parallel with the motion detector will lead to back-feeding the line voltage onto the detector's load terminal. Some electronic switches (such as photocells or motion sensors) may not tolerate this, and will sustain damage when trying to switch off.
    – A. I. Breveleri
    Commented Sep 21, 2020 at 23:04
  • @a.i. That seems improbable. Connecting all a device’s terminals to the same voltage means there would, at that point, be no voltage whatsoever on the device.
    – Harper - Reinstate Monica
    Commented Sep 22, 2020 at 0:28
  • @Harper - Reinstate Monica: Line voltage would be applied between the device's load terminal and the device's neutral terminal. - If the device does not require a neutral connection then no problem.
    – A. I. Breveleri
    Commented Sep 22, 2020 at 1:03
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Frame challenge. What you want is 1 switch to activate all the light (yet, the motion sensor only controls some). That's making people chase expensive obscura, and proposing marginally-Code solutions. What is easy is 2 switches to activate all the lights.

Blow out the motion sensor box to a 2-gang box. One gang gets the motion sensor. The next gang over gets a plain switch.

It's already true that the motion sensor gets always-hot. Extend/pigtail that so the plain switch also gets it.

Ditto ditto ditto, switched-hot.

Now, the switch at the motion sensor will override the motion sensor.

Note that if the motion sensor does not have a neutral, this will make the motion sensor lose power. That may wipe out its memory of normal day/night light levels in this location. So you might see some "motion sensor turning on lights in daylight" behavior for a day or two after overriding it. If you don't like that, get a motion sensor with a neutral.

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  • Not quite, because I do not want to motion sensor to turn on all the lights. I could add a third switch to this box to bypass the motion but that feels strange
    – Matthew
    Commented Sep 21, 2020 at 20:09
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    @Matthew Edited because I may not have been clear. I am saying to control the 10 lights with a switch as you have it; leave that alone. Then use both a motion sensor and a switch to control the 6 lights. Those two would be alongside each other in the same box. So 2 switches total + the motion sensor.
    – Harper - Reinstate Monica
    Commented Sep 21, 2020 at 20:30
  • That would work but I'd have to use two switches. Is there a viable solution without adding the new switch?
    – Matthew
    Commented Sep 21, 2020 at 21:57
  • How do you feel about relays? @Matthew
    – Harper - Reinstate Monica
    Commented Sep 22, 2020 at 0:21
  • I'm not opposed to them. I've done plenty of residential and hobbyist electrical work but I've never used a relay in a 115vac circuit before
    – Matthew
    Commented Sep 22, 2020 at 0:40

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