I bought an infrared + ultrasound occupancy (motion) sensing wall switch that advertised as not needing a neutral wire. However, it has an oddly color coded wire (green/yellow) that needs to be connected to ground, and I measured it to pass 0.1 to 0.2mA of current into ground.

I'm under the impression one should not put any current into the ground wire. But this switch is made by a well-known brand, perhaps small current is allowed?

This switch is not UL listed. A similar model from the same maker that requires a neutral wire, however, is UL listed.

 

Specifically how did you measure the current to ground?

 

Some ground current is allowed. Many electronic devices have so-called "Y" capacitors to ground. A very popular value is 4700pF; not coincidently, results in about .2mA of current at 120V. Yes, there is a legal limit, and is somewhere in the area of .5mA.

 

It is allowed under current code if the current draw is low enough. The growing need for neutrals in switch boxes has probably contributed to the 2014 code requirement of neutrals in all switches boxes. I suspect that in a few years using the ground won't be allowed as more and more switch boxes have neutrals.

I'd suggest if possible add a neutral and use the UL approved one.

 

Green yellow stripe is an international standard for ground.

I believe the code actually says there shall be no "objectionable current" flowing on grounds. It does not say none as that is physically impossible. That means it's up to the local or engineering authority where to draw the line between the theoretical zero current and the nebulous "objectionable current".

UL may have some specific level of leakage that is acceptable to meet their listing criteria, but it is certainly somewhere above zero.

To compare, a GFCI is not designed to trip until the 5-6 mA range.

 

I used a digital multimeter with AC mA and use the 20mA range which shows two digits after decimal point (e.g. 0.15mA).

However, I cheated a little and measured the current going into the neutral wire instead of ground. But I don't think it's going to make any difference.

The fact that this switch has two ground wires (a normal ground visibly connected to the metal case, and the green/yellow wire), leads me to think that connecting the green/yellow to neutral may be better if neutral is available. Otherwise; why don't they just tie the green/yelllow to ground internally.

When I bought this I didn't realize the switch is not UL listed and they have a UL listed version that requires neutral (which I prefer as well). I simply bought the first one I saw, not knowing the "no neutral needed" comes with a "price". I only dig into this after seeing the wiring diagram and realizing there's going to be a current in the ground wire.

Thanks to all who replied.

 

Do not tie the ground into the neutral.you could end up energizing grounded parts and creating a serious shock hazard.

 

Hi,just curious what meter would measure .2ma and how you did it?in seies or clamp-on.

 

I think there is a good reason why the switch wasn't U.L. Listed. I wouldn't use it.

 

I remember installing many occupancy sensors several years ago that were of the same type.... required a ground but no neutral. I believe they were commercial Watt Stoppers.

 

My guess is that the one without the neutral is intended for "replacement" use only and the one with the neutral is intended for new installations. Practically speaking there is very little anyone can do to enforce the "replacement" hardware that's out there as it does serve a legitimate need in the market.