UL 891

These requirements cover dead-front switchbo ard sections, interiors, and enclosures, rated 600 volts maximum, and intended to be employed as dead-fro ntswitchboards 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 s witches, circuit breakers, overcurrent protective devices, bus bars, or the like, and thenecessary 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 judgedunder 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 oilcircuit br eakers; 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.

Edition:

10th

Published:

12/23/1998