Working on installing switches to serve as disconnects for led signage in front of stores. These signs are fed by 120 volt time clocks. The signs are requiring us to turn on and off the switch going to the low volt ballast that feeds the sign. In essence we are bumping the voltage off and then on. Should this be required?
Yes you need a disconnect.
From the 2011 NEC..
600.6 Disconnects. Each sign and outline lighting system,
feeder circuit or branch circuit supplying a sign, outline
lighting system, or skeleton tubing shall be controlled by an
externally operable switch or circuit breaker that opens all
ungrounded conductors and controls no other load. The
switch or circuit breaker shall open all ungrounded conductors
simultaneously on multi-wire branch circuits in accordance
with 210.4(B). Signs and outline lighting systems
located within fountains shall have the disconnect located
in accordance with 680.12.
Exception No. 1: A disconnecting means shall not be required
for an exit directional sign located within a building.
Exception No. 2: A disconnecting means shall not be required
for cord-connected signs with an attachment plug.