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Revision B MX28B-1200 PRODUCT MANUAL
MX28B-1200/2400 15
5.1.7 Ventilation
The rectifiers have fans that provide front to rear airflow for internal cooling. The MX28B
housing should mounted such that there is free airflow to the front and top of the unit. [Refer to
Section 4.8 for environmental characteristics.]
5.2 AC Service and Ground Connections
*****
WARNING *****
Ensure that all of the dc and external ac circuit breakers are in the OFF position prior to
connecting service to the power plant. Confirm that all voltages have been removed
including any battery sources before proceeding.
The MX28B dc power plant requires the
supply of 208/220/240V ac, single-
phase, 50/60 Hz power through
individual external 20-amp two-pole
circuit breakers to the ac input terminal
block connections for each rectifier in
the system. The ac wiring, from the ac
input terminal block connections to the
hot-pluggable ac input connector for
each rectifier, is factory installed.
The ac input enclosure, located at the top
rear of the MX28B housing, is provided
with nine ¼ -inch conduit pilot holes in
the top plate (Figure 5-2). Remove the
ac input enclosure from the box frame in
order to punch or drill the appropriate
number of conduit openings for the
conduit size(s) desired. Do not leave the
ac input enclosure in place when punching
or drilling holes in order to prevent metal
pieces from falling into the power system.
AC wiring passing through the conduit will be routed through
the access opening in the ac input enclosure into the vertical
wiring channel where safety ground bar and rectifier input
terminal blocks are located. The terminal block(s) is labeled
as Rectifier 1 through Rectifier 4 with each position having
inputs designated “L1” and “L2” for connection of the two ac
wires (Figure 5-3). Each terminal block represents
connections for one shelf, with positions 1 through 4
corresponding to the rectifier shelf positions numbered from
left to right as view from the front.
The suggested wire size is #10 AWG rated at 90°C or higher;
however, the ambient temperature and number of wires in a
AC Input
Enclosure
Access
Opening
Vertical channel
for AC wiring
Figure 5-2 AC Wiring Access
Figure 5-3 AC
Terminal Block