I really thought that 408 only applied to panels with OCPDs, but that isn't what the scope says. A dimmer panel does control lighting circuits and looks to me like it would fall within the scope of the article. If it is within the scope then 408.15 applies.This article covers the following:
(1) All switchboards, panelboards, and distribution boards installed for the control of light and power circuits
(2) Battery-charging panels supplied from light or power circuits
1.6 These requirements do not cover the following switchboard types: preset and dimmer control (theater) , live front, railway control or electrification, units containing oil circuit breakers; or constructions intended only for receiving motor control center units.
