This month, Clint is sharing an article on controlling emergency lighting, the codes involved, and how to design those systems. Here's what he has to say about the article:

Emergency egress lighting is required in commercial spaces to ensure the safe exit of building occupants under loss of normal power. In order to minimize energy consumption in a facility, these lights should be controlled in order to save energy when the building is not occupied or when the lights are not required for other reasons. The National Electrical Code requires that any controlled, code required egress light be equipped with automatic load control relay (see N.E.C. 700.2 and 700.25). These devices automatically override any lighting control to the emergency fixture and bring the fixture to full light output under loss of normal power (the emergency fixture is powered by an alternate, emergency power source).

 

The article referenced below is a great resource for these requirements, and for how to design these systems. It  does not cover applications where 0-10V dimming is required on the emergency lighting. Dimming mentioned in this article is standard two-wire dimming. Override of 0-10V dimmed fixtures is straightforward...the power conductors are overridden using a UL924 shunt device just as would be done with any switched fixture. Since 0-10V dimming operates with 10V (open circuit) causing the light to be completely on and 0V (short circuit) causing the light to be completely dimmed, all that is needed is a second relay to open the 0-10V dimming circuit. This can be accomplished using a second UL924 rated device, or a dual relay shunt device, such as Functional Devices ESRN which is UL 924 listed and shunts the line voltage and opens the 0-10V in a single device.

Read the full article here!