Filter
Top Products
MX28B400 +24 VDC User’s Manual Page 6
Ventilation
The rectifier modules for this system 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, top,
and bottom of the unit. [Refer to Section 6.5 for environmental characteristics.] Free airflow
should be ensured so that the power system can provide full power without de-rating.
3.3. AC Power Connections
WARNING: Ensure that all of the external dc and 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 power plant requires the supply of nominal 230 Vac single-phase, 50/60 Hz power
through individual external 20-amp circuit breakers to the ac input terminal block connections for
each rectifier module in the system. Two rectifier modules are required to accommodate the full
ac input voltage range. The 1MRF28H27BV rectifier is designed for the standard 208/220/240
Vac input service, while the 1MRF28H27BV50 is used for the 277 Vac input. The ac wiring, from
the 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 right rear of the MX28B housing, is provided with two
one-inch conduit entry holes and an access cover. Inside, a terminal strip for ac input power
connection and a separate “Earth Ground” bar for connection of the safety ground wire(s) are
provided. The terminal block(s) is labeled as Position 1 through Position 4 with each position
having inputs designated “L1” and “L2/N” for connection of the 2 ac wires. Positions 1-4
correspond to the rectifier shelf positions from left to right.
The suggested wire size is #10 AWG rated at 90°C or higher; however, the ambient temperature
and number of wires in a conduit must also be considered in accordance with NEC
requirements. It is suggested that feeds for four rectifiers (8 wires) and one safety ground wire
be run in a one-inch conduit; however, be sure to follow any local electrical wiring codes.
If the ac input power is provided from a three-phase distribution panel, the circuit breaker
positions should be selected such that the load is balanced as much as possible.
WARNING: The MX28B power plant is supplied from a nominal 230Vac, 60
Hz source. Keep the ac input enclosure in place when the system is
operational or energized.