Thermo King T-500R Maintenance Manual page 135

When the voltage sensed rises above 165 volts AC and all three phases are present, the module ER wire will output 12 volts
DC after the conditions exist for 2 to 4 seconds. This signal informs the microprocessor that electric standby operation is possible.
If the voltage drops below 160 volts AC or a phase is lost, the ER output is turned off after the condition exists for 3 seconds. The
module continues to monitor the power and the module ER wire will again output 12 volts DC within 2 to 4 seconds after the
voltage rises above 165 volts AC and all three phases are present.
If phase orientation is L1, L2, L3 the 7EB wire will output voltage to energize the appropriate phase rotation contactor MCA.
If phase orientation is L1, L3, L2 the 7EC wire will output voltage to energize the appropriate phase rotation contactor MCB. The
7EB and 7EC wires are interlocked to prevent both phase contactors from being energized at once.
If the SP input is grounded, the module will now be set for single-phase operation. In this case only the Brown and Gray wires
are used and the Black wire is taped off.
Connections to the module are shown in the tables below.
Power Connections
Input Description
8 Nominal 12 volt DC power to the phase select module
CH Chassis ground
Inputs
Input Description
L1 This Brown wire supplies standby power L1 to the phase select module.
L2 This Gray wire supplies standby power L2 to the phase select module.
L3 This Black wire supplies standby power L3 to the phase select module.
7EA If 12 volts DC is supplied, then output 7EB or 7EC will be at 12 volts DC
SP If this wire is connected to chassis ground the module will operate in single-phase mode.
SP- This is an internal ground for the module. If SP-GND is jumpered to SP then the module will be
GND set to operate on single phase.
Outputs
Output Description
7EB If phase orientation is L1, L2, L3 then this wire will provide 12 volts DC to energize the
appropriate phase rotation contactor MCA. The 7EC wire is interlocked to prevent both phase
contactors from being energized at once.
7EC If phase orientation is L1, L3, L2 then this wire will provide 12 volts DC to energize the
appropriate phase rotation contactor MCB. The 7EB wire is interlocked to prevent both phase
contactors from being energized at once.
ER This wire will output 12 volts DC to the microprocessor 2 to 4 seconds after the voltage rises
above 165 volts AC and all three phases are present. If the voltage drops below 160 volts AC
or a phase is lost and the condition remains for 3 seconds, the output is turned off. The module
continues to monitor and will again output 12 volts DC 2 to 4 seconds after the power returns to
normal (voltage rises above 165 volts AC and all three phases are present).
Electrical Maintenance 8-15