Originally Posted by Speedy Petey
I'm sorry, but I don't buy it.
There should be NO current on the equipment ground, period, and I'm not sure what the EG has to do with the grounded conductor (neutral) being required in switch boxes. I can see your point only in that dumb people were using the EG as a neutral in places where a switch loop existed and an OC switch was install that required a neutral. This creates a tiny amount of circuit current on the EG systems which is NOT good.
The equipment ground and the neutral are two different things. I have never seen an OC switch that required an equipment ground to work properly.
Copied and pasted from an IAEI article found here
Grounded Circuit Conductors at Switch Locations
New requirements in the latest edition of the Code requires that where switches control lighting loads such as luminaires, ceiling paddle fans, etc., and are supplied by a general-purpose branch circuit that is grounded, the grounded circuit conductor (generally neutral conductor) for the controlled lighting circuit is required to be provided at the switch location. An exception to this requirement permits the grounded (neutral) conductor to be omitted from the switch enclosure where one of the following conditions applies:
(1) Conductors for switches controlling lighting loads enter the box through a raceway, with the raceway having sufficient cross-sectional area to accommodate adding a grounded conductor at a later date or (2) where cable assemblies such as Type NM cable enter the box through a framing cavity that is open at the top or bottom on the same floor level, or through a wall, floor, or ceiling that is unfinished on one side [see NEC
Many electronic lighting control devices, such as occupancy sensors require a standby current to maintain a ready state of detection for the function of these devices. This also allows immediate switching of the load to the “on” condition. These types of devices require standby current when they are in the “off” state as well. These devices typically utilize the grounded conductor for the standby current flow. In some situations, such as where the grounded conductor is provided at the lighting outlet location, a grounded conductor is typically not provided in the switch box for switches controlling lighting loads. When a snap switch is replaced with an occupancy sensor at a later date, installers have typically employed the equipment grounding conductor for the standby current of these control devices. This is not a good practice due to the introduction of circulating current onto the equipment grounding conductor. Occupancy sensors are permitted by UL 773A to have a current of up to 0.5 mA on the equipment grounding conductor.
Current flowing at the load when the device is presumed to be off could create a potential risk to installers.