clearly indicated.
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Each motor control center shall be designed for operation on 480-volts ac,
3-phase, 60-Hz system, and the equipment shall conform to all the
applicable requirements of NEMA ICS 1, NEMA ICS 2, NEMA ICS 4and NEMA ICS 6.
Vertical sections and individual units shall be listed and labeled under
UL 845 where ever possible. In lieu of the UL listing, certification from
any nationally recognized, adequately equipped, testing agency that the
individual units and vertical sections have been tested and conform to the
UL requirements of that agency will be acceptable when approved by the
Contracting Officer. The motor control center shall be NEMA Class II,
[Type B] [Type C] [Type B or C as indicated in the bid item list], motor
control centers in accordance with NEMA ICS 2.
2.6.1
Enclosures
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NOTES: Stand alone front access line-ups are most
desirable for ease of operation and maintenance, but
particular installations may require specialized
arrangements, such as back-to-back mounted units.
Consult manufacturers for specialized requirements.
NFPA 70 Article 430H lists the various NEMA
enclosure types for Motor Control Centers. Designer
should ensure that the NEMA type specified meets
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Each motor control center shall consist of the required number of vertical
sections of 2250 mm 90 inches nominal height, bolted together, with steel
channel sills and suitable for mounting against a wall. Vertical section
shall be 510 mm 20 inches deep and buses, control wiring, control
cable supports, and clamps shall be accessible from the front. Enclosure
shall be NEMA Type [1 gasketed] [12] [3R]. The control centers shall be
fabricated from smooth select steel sheets shaped and reinforced to form
rigid free-standing structures. Metal thickness for enclosures shall be
not less than specified in NEMA ICS 6 without exception. Vertical edges of
sections exposed to view shall be so fabricated and bolted that the joints
will not pass a 1.6 mm 1/16 inch gage. Each structure shall be designed
for addition of future sections required. Individual compartments shall be
isolated from adjacent compartments.
2.6.1.1
Unit Compartments
Each operating unit shall contain equipment as shown on the drawings,
mounted in an individual cell. The unit assembly, except main circuit
breakers, panelboards and auxiliary control devices, shall be drawout type
removed from the front, without rear access or disturbing other units in
the control center assembly. All drawout type unit assemblies shall have
positive guide rail system to ensure alignment of connection to vertical
bus. Units shall be mechanically interlocked with the door to prevent
removal while in the energized position. Each removable unit shall have
provision for padlocking in a position in which it is disconnected from the
vertical bus although not removed from the stationary structure. All
ventilating openings shall be provided with corrosion-resistant
insect-proof screens on the inside. Bus closing plugs shall be provided
SECTION 16403A
Page 18