UL - 891
UL Standard for Safety Dead-Front Switchboards
|Publication Date:||23 December 1998|
These requirements cover dead-front switchboard sections, interiors, and enclosures, rated 600 volts maximum, and intended to be employed as dead-front switchboards in accordance with the National Electrical Code, NFPA 70.
In this standard the term switchboard is intended to refer to a dead-front switchboard.
For the purpose of these requirements, a switchboard is considered to be a large single panel or frame having dead-front panels on which may be mounted meters, pilot lights, fixtures for illumination, manually or automatically operated switches, circuit breakers, overcurrent
protective devices, bus bars, or the like, and the necessary wiring.
If the inside dimensions of the enclosure of a switchboard section are
less than 65 inches (1.65 m) high or 12 inches (305 mm) deep, the enclosure is to be judged under the requirements of this standard, but the internal parts and wiring are to be judged by the applicable
requirements in the Standard for Panelboards, UL 67.
These requirements cover switchboards intended for the control of
electric light and power circuits.
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.
These requirements cover switchboards for use on circuits having
available rms symmetrical short-circuit currents of not more than 200,000 amperes.