NFPA 70 National Electrical Code 2023 Article 700 Emergency Systems 700.23-700.28: 700.23 to 700.28 Dimmers, relays, luminaires with control inputs and Class 2 control

A dimmer or relay system listed for emergency use may control emergency lighting and on normal power failure energise only the circuits needed for minimum emergency light through a control bypass, sensing normal power upstream of the transfer switch where fed from a normal/emergency source, with its branch circuits wired per Part II. Luminaires with control inputs, branch circuit emergency lighting transfer switches, automatic load control relays (which may not serve as transfer equipment) and devices carrying both control signalling and Class 2 emergency power must be listed for the purpose.