Motion sensor switch wiring

[gs8212]

I'm replacing a simple 15 amp light switch with a 15 amp motion sensor for an overhead light. The unit has wires and caps rather than screws I think because the wires connect to circuit boards inside the unit.

What threw me is the sensor only has 2 black wires and a green, no neutral. I expected a black and white. And the instructions show 2 blacks coming in and connecting with the 2 blacks on the sensor; green to green; and nothing about the neutral.

So do I pigtail the 2 blacks on the sensor to the power; cap off the neutral; and connect the green to green? Haven't run into this before and know just enough to get myself in trouble.

 

[nehog]

And the instructions that came with the switch say?

 

[Alchymist]

I'm replacing a simple 15 amp light switch with a 15 amp motion sensor for an overhead light. The unit has wires and caps rather than screws I think because the wires connect to circuit boards inside the unit.

What threw me is the sensor only has 2 black wires and a green, no neutral. I expected a black and white. And the instructions show 2 blacks coming in and connecting with the 2 blacks on the sensor; green to green; and nothing about the neutral.

So do I pigtail the 2 blacks on the sensor to the power; cap off the neutral; and connect the green to green? Haven't run into this before and know just enough to get myself in trouble.

??? If you are replacing a single toggle switch, and you have a black and a white wire, you have what's called a "switch leg", using the white wire as one leg of the switch. Just hook the black wires on the new switch to the black and white wires from the old switch. The white wire on the original switch is not a neutral.

 

[gs8212]

...The white wire on the original switch is not a neutral.

Excellent. I think I just saw that type of circuit in a book on wiring and totally forgot it. This switch must be at the end of the run, with the light fixture between the switch and the power. The black brings power to the switch (bypassing the light) and the white takes the power back to the light? Did I get that correct?

 

[gs8212]

And the instructions that came with the switch say?

The instructions only give you a picture and say "connect it". The picture shows 2 blacks (labeled as such) connected to 2 blacks, and green to green. No indication of a white.

 

[Mustang51js]

Excellent. I think I just saw that type of circuit in a book on wiring and totally forgot it. This switch must be at the end of the run, with the light fixture between the switch and the power. The black brings power to the switch (bypassing the light) and the white takes the power back to the light? Did I get that correct?

If those are the only two colored wires in the box then yes. It doesn't mean it's the end of the line,just the way some people wire stuff, usually a commercial electrician would do something like that.

 

[Alchymist]

If those are the only two colored wires in the box then yes. It doesn't mean it's the end of the line,just the way some people wire stuff, usually a commercial electrician would do something like that.

Commercial electrical is usually conduit. The switch leg method was quite common in residential wiring until a recent code change required a neutral in every switch box.

 

[justsam]

Normally a neutral is required in order to power the electronics in the "smart switch", as others have pointed out it is now a requirement o have a neutral in all switch locations.

Does the switch indicate what type of loads it can switch? There are ways of providing power for the electronics even on a switch leg if the load is resistive such as an incandescent bulb. Other load types may not provide the path to neutral.

 

[alfredeneuman]

The black brings power to the switch (bypassing the light) and the white takes the power back to the light? Did I get that correct?

Not quite. The white wire is the hot side and the black wire goes to the light.

Make sure to connect the green to a ground wire, the switch needs a ground reference in order to work correctly. It carries a little minute bit of current, the same as the neutral in sensors with a neutral connection.

 

[gs8212]

Not quite. The white wire is the hot side and the black wire goes to the light.

Make sure to connect the green to a ground wire.

Definitely connected the green to green. and then black to black and white to black. I guessed but should have tested which was power. White was not marked with tape so assumed it was taking power back to the light. Maybe assuming and electricity don't mix.

Normally a neutral is required in order to power the electronics in the "smart switch", as others have pointed out it is now a requirement o have a neutral in all switch locations.

Does the switch indicate what type of loads it can switch?

Is it an issue that there isn't a neutral in the switch location? Won't burn my house down will I?

I think I understand your question on loads. Package says:

• 150 W CFL, LED
• 200 W MLV
• 250 W incandescent, halogen, ELV
• 2 A ballasts

I have the switch controlling 2 100-W LEDs.

 

[alfredeneuman]

Is it an issue that there isn't a neutral in the switch location? Won't burn my house down will I?
.

No, the current on the ground is just a few milliamps (Thousandth of amps)

 

[gs8212]

I have on last question. The switch box is in the garage and has 2 switches in it. I assumed both were on the same 15 amp breaker because they were in the same switch box (bad idea).

Being the careful person I am, I flipped the breaker, lights went out in the garage, and I then tested both switches with my little light-with-2-wires-thing and everything came up negative. I took my tester inside and checked a receptacle to make sure my light tester worked, which it did, and I checked all the screws on both switches a second time; everything came up negative.

I installed the sensor switch and as I was pushing the wires back into the box I got the flash-bang. I couldn't understand how it happened. It finally dawned on me this a.m. that they were likely on different circuits, and low and behold there was a tripped breaker in the box.

My question is why did my tester not pick-up power on the screws of the other switch? The one other piece of info that may be relevant is the original switches had the wires pushed in the back rather than wrapped on the screws. Could that prevent me from detecting power to the other switch's screws? I was too lazy (another bad idea) to pull the black off the other switch and test it there for power - assumed the screws would tell me.

Also wondering why I tested negative for power on the other switch's screws, yet it appears that the flash-bang was from the bare ground wire of the sensor touching one of the screws?

As usual, any insight appreciated.

 

[Elginz]

The switch was tuned off, so no power across the screws.

 

[Mustang51js]

Commercial electrical is usually conduit. The switch leg method was quite common in residential wiring until a recent code change required a neutral in every switch box.

Around here you don't see that often,only with some older bx wires or knob and tubing. It just really depends on the installer and how they were taught. I've always liked to bring nuetral into switch box before it was required,but I know on a lot of commercial stuff I've done we just put a junction box above the drop ceiling and a two wire down to switch

 

[Mustang51js]

Were you testing from ground to screws or just screw to screw

 

[gs8212]

Were you testing from ground to screws or just screw to screw

The switch was tuned off, so no power across the screws.

I believe I tested screw to screw. It is a 3-way with switch in the front hallway so not sure if on or off. Definitely "off" after that ground touched.

 

[Mustang51js]

Screw to screw won't show any power since it's the same phase going through the switch

 

[Mustang51js]

Might show like 40 volts but prob your testor doesn't pick up that low of voltage

 

[gs8212]

I've always liked to bring nuetral into switch box before it was required,but I know on a lot of commercial stuff I've done we just put a junction box above the drop ceiling and a two wire down to switch

Commercial electrical is usually conduit. The switch leg method was quite common in residential wiring until a recent code change required a neutral in every switch box.

Mustang51js and Alchymist -- If a neutral has to come to a switch box per recent code, then it sounds like I need to run the extra cable necessary to get the power over to the switch first to then control the power to the light in the traditional (?) way, so that there is a neutral connection in the switch box that allows return from the light all the way back to the breaker box?

 

[Oggy]

what model/brand switch did you buy?

 

[Mustang51js]

Mustang51js and Alchymist -- If a neutral has to come to a switch box per recent code, then it sounds like I need to run the extra cable necessary to get the power over to the switch first to then control the power to the light in the traditional (?) way, so that there is a neutral connection in the switch box that allows return from the light all the way back to the breaker box?

Not really following you but your fine the way it is,most switches don't use the nuetral, your neutral is up in the light box. Just use a switch that doesn't need a neutral hooked to it to work

 

[gs8212]

Thanks much Mustang. Appreciate the knowledge and experience you guys bring.