3-way and 4-way switching on 208V fluorescent lights

Is there anything in the 2011 NEC that requires all ungrounded conductors to be opened by the light switch? I've seen 410.104(B) cited in similar situations but I can't see how a wall switch can be considered a 'switching device of auxiliary equipment.'

Each lighting circuit will be served by a 2-pole, lockable off, branch circuit breaker. The fixtures are 6-lamp T5HO and will be installed in a Class I, Div. 2 hazardous area.



Staff member
The ballast is auxiliary equipment to the lamps.

410.104 Electric-Discharge Lamp Auxiliary Equipment.
(A) Enclosures.
Auxiliary equipment for electric-discharge
lamps shall be enclosed in noncombustible cases and treated
as sources of heat.

(B) Switching. Where supplied by the ungrounded conductors
of a circuit, the switching device of auxiliary equipment
shall simultaneously disconnect all conductors.


Staff member
Unfortunately, the end result is that you will need to find full double-pole double-throw switches for the 3-way locations and four-pole double-throw (or four-pole crossover) switches for the 4-way locations.
Or use control wires and a contactor. :)


Electron manager
If using control wires and a contactor you may even save more by using class 2 control circuit and CL2 cables.