Occupancy sensor

[Tdubya90]

Can anyone explain to me why it says to terminate the ground wire on the common screw? Seems weird.

Was gonna post a picture but there doesn't seem to be a way.

It's for a 3 way occupancy sensor eaton os306u

 

[LarryFine]

Can anyone explain to me why it says to terminate the ground wire on the common screw?

Well, don't do that!

Was gonna post a picture but there doesn't seem to be a way.

Where is the pic now?

It's for a 3 way occupancy sensor eaton os306u

I see: "d. The sensor green wire will connect to the ground wire in the wallbox."

PDF: https://www.eaton.com/content/dam/e...nsors/os306u-and-vs306u-instruction-sheet.pdf

 

[LarryFine]

I found it: "b. Connect the bare ground wire in the wallbox to the common terminal (usually a black screw or a marking such as COM or COMMON near the terminal) on the 3-way switch."

It doesn't compute, but that's under one specific switching situation, I'll have to look more to make sure it isn't an error.

 

[ptonsparky]

I only ever referred to these two wires as travelers.
Nothing else.

 

[don_resqcapt19]

I found it: "b. Connect the bare ground wire in the wallbox to the common terminal (usually a black screw or a marking such as COM or COMMON near the terminal) on the 3-way switch."

It doesn't compute, but that's under one specific switching situation, I'll have to look more to make sure it isn't an error.

This type of switch is what triggered the rule that the neutral conductor to be run to the switch locations. Most older electronic switches used the EGC as the neutral conductor to power the switch electronics. The exception to 404.2(C) only permits the use of the EGC as part of the power circuit for the internal electronics.

402.2(C) ...The grounded conductor shall be extended to any switch location as necessary and shall be connected to switching devices that require line-to-neutral voltage to operate the electronics of the switch in the standby mode and shall meet the requirements of 404.22.
Exception:
The connection requirement shall not apply to replacement or retrofit switches installed in locations prior to local adoption of 404.2(C) and where the grounded conductor cannot be extended without removing finish materials. The number of electronic control switches on a branch circuit shall not exceed five, and the number connected to any feeder on the load side of a system or main bonding jumper shall not exceed 25. For the purpose of this exception, a neutral busbar, in compliance with 200.2(B) and to which a main or system bonding jumper is connected shall not be limited as to the number of electronic lighting control switches connected.

 

[Tdubya90]

Thanks Larry. Yes, very weird that it says that. That sensor was junk anyways and I was reading 20 volts on the ground if it were wired up that way. So I bought a Lutron instead.

Don, that's different because in that case it's not using the ground as the neutral. It shows to wire it that way on both the neutral present and neutral not present instructions.

 

[LarryFine]

Generally speaking, these devices replace one 3-way switch, and then it does all of the controlling of the load, and the remaining 3-way (or a companion controller) acts as a wired remote-control of the main device.

This has been done since the X10 days. One traveler carries the hot or switched hot from the main device to the load through the other switch box, and the remaining traveler carries the remote switching.

I don't get why they say the EGC instead of the neutral.

 

[Tdubya90]

Yes, I get that. But why on earth does it say to wire it to the ground? The lutron I replaced it with didn't utilize the neutral at all. The secondary switch had basically two travelers terminated to the poles on the single pole switch. Idk man, either they messed up or they just have an impressively weird way of doing it. The sensor itself was not very good tbh. Just a warning to others to steer clear of Eaton occupancy sensors.

 

[James L]

I'm not an electronics guy, but I think it depends if the switching is solid state or if it has relay needing neutral for the coil.

Same thing with photo eyes, exterior motion sensors, and some wireless switches.

The ones with a neutral are supposed to be more accurate. Also, I believe they are usually able to handle higher current.

For a frame of reference on this, Lutron makes several Caseta devices such as dimmers, on/off switches, etc. The ones rated at 150w (1.25 amps) don't need a neutral. But the ones I've seen rated for 5 or 6 amps do need a neutral.

Again, I think this is how and why, but I will stand corrected by anyone who knows better.

 

[ActionDave]

Yes, I get that. But why on earth does it say to wire it to the ground? The lutron I replaced it with didn't utilize the neutral at all. The secondary switch had basically two travelers terminated to the poles on the single pole switch. Idk man, either they messed up or they just have an impressively weird way of doing it. The sensor itself was not very good tbh. Just a warning to others to steer clear of Eaton occupancy sensors. View attachment 2573711

Those are instructions that are used when you have a switch location and no neutral in the box to keep the electronics powered when the switch is off. There is usually another set that shows using the neutral if present. The device will function hooked up to a neutral no matter what the instructions say. The device can't tell if it's hooked up to a neutral or an EGC, it just knows it's got a circuit to keep it's little brain powered so the motion sensor will work when the switch is off.