UL 845:2021 pdf download.STANDARD FOR SAFETY-Motor Control Centers.
1.1 Products covered
1.1.1 UL 845 applies to motor control centers to be used in accordance with the U.S. National
Electrical Code, ANSI/N FPA 70, CSA C22.1, Canadian Electrical Code, Part 1, and the Mexican Electrical
Installations (Utility), NOM-00 1-SE D E.
1.1.2 These requirements cover motor control centers for use on circuits having available short-circuit currents not more than 200 000 A rms symmetrical or 200 000 A dc.
1.1.3 This standard applies to single- and three-phase 50 and 60 Hz and dc motor control centers rated not more than 1000 V ac or dc.
1.1.4 Requirements for fire pump controllers are as provided in Annex C, item 11.
1.2 Products not covered
These requirements do not cover switchboards or panelboards intended for the control of electric light and power circuits, nor do they cover an individual unit for this purpose. Such units, however, that consist of manually or automatically operated switches, branch-circuit or service-circuit circuit-breakers, overcurrentprotective devices, or the like may be used within a motor control center.
1.3 Equipment
1.3.1 A motor control center can contain, but is not limited to, any combination of equipment such as the following:
a) full-voltage reversing or non-reversing combination motor control units;
b) full-voltage multispeed combination motor control units;
C) reduced-voltage part-winding, wye-delta or auto-transformer combination motor control units;
d) solid-state industrial controllers, such as adjustable-speed drives, programmable controllers, protective relays, and the like;
e) lighting or distribution panelboards;
f) feeder-tap units;
g) incoming-line equipment, such as main lugs, fusible switch, isolation switch, or circuit-breaker;
h) control or lighting transformers;
i) special equipment assemblies;
j) combination contactor units.
1.3.2 The foregoing equipment can contain, but is not limited to, such items as pushbuttons, selector switches, indicating lights, control transformers, control circuit fuses, and auxiliary devices incorporated as an integral part of the units.
1.4 Units of measurement
The first values given are SI (metric) units. Alternate measurements shown in parentheses are US customary units, which sometimes are not strict conversions.
2 Normative references
The normative references listed in Annex C contain provisions which, through reference in this text, constitute provisions of this standard. Any undated reference to a code or standard appearing in the requirements of this standard shall be interpreted as referring to the edition of that code or standard and all published changes up to the time when this standard was approved.
In Canada, general requirements are as indicated in Annex C, item 16.
3 Definitions
3.1 For the purposes of this standard, the following apply.
3.2 auxiliary devices — types of devices such as indicating meters (instruments), current transformers, control devices, control relays, timers, protective relays or protective devices, communications devices, etc.
3.3 available short-circuit current — the short-circuit current available at the equipment line terminals plus any motor contribution. The available ac short-circuit current is expressed in rms symmetrical A.
3.4 bus, horizontal — a bus that extends through a motor control center section.
3.5 bus, vertical — a bus that serves the units in a section and that originates from the horizontal bus. This bus may be replaced by insulated wiring.UL 845 pdf download.