I had a mixed experience installing the new-ish Maestro occupancy sensor switch. It uses a ground connection — to equipment ground — to power low-power electronics in the sensor. This makes installations in old wiring applications straightforward, but complicates new work installations, since the most common areas for an occupancy sensor will be kitchenettes, bathrooms, laundry areas and utility rooms that all may have plumbing or other features requiring GFCI protection.
Occupancy sensors mounted with GFCI — but not protected by the GFCI function!
The use of equipment ground for a current path to power the sensor electronics means that the sensor may not be installed on GFCI circuits designed to prevent shock and electrocution hazard from precisely this type of current path. The GFCI sees the unbalanced current to ground via the equipment grounding path as a ground fault. I have not tested the sensor on AFCI circuits, which also include ground fault detection, albeit at a higher threshold (more current before trip).
In retrofit applications, it may be installer’s option, whether to extend GFCI (or AFCI) protection to the added switch. In new construction, all residential circuits will be either AFCI protected or GFCI protected. If you’re installing an occupancy sensor on a GFCI laundry or bathroom circuit, then the sensor portion of the circuit must be on the GFCI-protected portion of the circuit. This won’t work with this device, since the device will cause the GFCI receptacle or breaker to trip.
On the other hand, the device otherwise installs and configures nicely, with simple buttons and instructions for modifying the sensible default occuancy 5-minute turnoff setting for testing, or different off-timer settings from 1min to (?) 30min. It’s a nice-looking switch and accommodates all lamp types from simple filament incandescents to CFLs, LEDs, magnetic and electronic low voltage. It is amazingly lightweight, leading me to worry about longevity, and yet it makes an audible click in switching the circuit, so I guess the contactor is somewhat robust.
See also:
Licensed Electrician Robert Monk Maestro® Occupancy Sensing Switch — GFCI incompatible Copyright Robert Monk, 2012
Source: http://www.phillylicensedelectrician.com/maestro-occupancy-sensing-switch-gfci-incompatible/
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