terminal block marking strips may be according to the Contractor's standard
practice; however, additional wire and cable designations for
identification of remote (external) circuits shall be provided for the
Government's wire designations. Prints of drawings submitted for approval
will be so marked and returned to the Contractor for addition of the
designations to the terminal strips and tracings, along with any
rearrangement of points required.
2.5
SPACE HEATERS
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NOTE: Heaters should be connected to an external
power source in installations where the motor
control center will not be energized continuously.
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Space heaters shall be provided where indicated on the drawings and shall
be controlled using an adjustable 10 to 35 degrees C 50 to 90 degrees F
thermostat, magnetic contactor, and a molded-case circuit breaker [and a
480-120 volt single-phase transformer]. The space heaters shall be
250-watt, 240 volt strip elements operated at 120 volts and shall be
[supplied from the motor control center bus] [wired to terminal blocks for
connection to 120-volt single-phase power sources located external to the
control centers]. The contactors shall be open type, electrically-held,
rated 30 amperes, 2-pole, with 120-volt ac coils.
2.6
MOTOR CONTROL CENTERS
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NOTES: This specification covers single stand alone
lineup with front access. Not all arrangements can
be listed and labeled under UL 845. Consult
manufacturer's literature and UL listing
availability for specific arrangements.
Auxiliary motor control centers should be NEMA Class
II, Type B or C, as applicable. Type C construction
includes master section terminal boards at the top
or bottom of each vertical section and complete
control wiring and power wiring for NEMA Size 3 and
smaller controllers between the unit assemblies in
each section and the master terminal boards. Type C
construction is preferred and should be specified
whenever a considerable amounts of interpanel
control wiring or external control circuits is
required. Designer should consider number of
terminal blocks required for type C construction and
ensure that there is sufficient space and access.
Where the unit assemblies consist primarily of
feeder tap units with circuit breakers to supply
power loads or starter units for individually
controlled motors (such as for pumps in pumping
stations), and very little interpanel and external
control wiring is required, the less expensive Type
B construction, which does not include master
section terminal boards, should be specified. If
the procurement includes both types of control
centers, the type of each control center should be
SECTION 16403A
Page 17
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