62-12259 4–2
To start the unit, place the SROS in the run position.
• Power flows from the SROS out of the display module through DM-7 to the J1 jumper fuse (F15) to splice
point 31 (SP31).
• From splice point 31 to MSM and OGF (SP31 to 3MSM-35 and SP31 to HVB1-J to HVB4-1 to OGF-12+).
• Power flows through the OGF to splice point 32 (OGF-S+ to HVB4-4 to HVB1-M to SP32) from splice
point 32 to the high pressure switch and the MSM (SP32 to HPS-A and SP32 to 2MSM-16), through the
high pressure switch to the power module (HPS-B to PM-22).
• Power flows through the PM to the positive side of the K1 PER relay coil.
• The input signal to 3MSM-35 wakes up the control system and the input from the OGF to 2MSM-16 tell
the control system it is good to energize the K1 PER relay by supplying the ground circuit.
When the K1 PER relay is energized and the contacts close, power is supplied to:
• F8 fuse, which supplies power to PM-2 (Optional)
• F9 fuse, which supplies power to PM-5 to SP30. SP30 connects to LB-B and SATPWR-A
• F10 fuse, which supplies power to PM29 and PM-17. PM-29 supplies power to the PRM-12+ (PM-29 to
HVB1-G to HVB3-and to SP81 to PRM-12+) and (PM-17 to ES-E)
• F11 fuse which supplies power as required to the evaporator fan contactor (EVCON), auto fresh air relay
(AFAR) (optional), condenser fan contactor 1 and 2 (CDCON1 and CDCON2), liquid injection solenoid
valve (LIV), stater solenoid (SS), electric fuel pump (FP) (optional), engine control unit (ECU), and the
fuel heat relay (FHR) (optional).
4.3 Engine/Electric Operation
Engine or Electric Operation is chosen at the display panel (Refer to Section 3.5).
With Electric Operation chosen, the PRM will determine which contactor to energize (PSCON1 or PSCON2). If the
PRM can not detect which contactor to energize alarm 00074 "PHASED REVERSED" will become active.
Energizing a power supply contactor reverses its contacts to allow power from the power plug while the engine is
shutdown and power from the generator is locked out.
When Engine Operation is chosen the generator contactor (GENCON) is energized. Energizing GENCON reverses its
contacts to allow the engine and generator to operate while power from the power plug is locked out.
Once the power selection is made:
• The microprocessor / stepper module will open the compressor suction modulating valve (CSMV), evapora-
tor expansion valve (EVXV), and economizer expansion valve (ECXV) to equalize system pressure, and
then bring the valves to a predetermined position before the unit starts.
• The contactor control board will energize the compressor, contactor or heater contactors as required, and
the power module will energize the condenser fan motors, contractors, evaporator fan motor contactor as
required.
4.3.1 Soft Start (Bump Start)
On command to start the compressor the control system will determine if there is a need to perform a Soft Start.
Soft Start is performed to clear refrigerant from the compressor and/or return oil; Soft Start will be activated if:
• Compressor has been off for more than twenty- four hours or
• Compressor has been off for over two hours, suction and discharge pressure are within 10 psi (0.7 bar) or
• Compressor has been off for more than two hours and suction pressure is above discharge pressure
During Soft Start the control system will de-energize the liquid injection valve (LIV), economizer expansion valve
(ECSV) and energize the buzzer for five seconds. Then the compressor will operate for one second on, followed by
nine seconds off. The on/off sequence may repeat up to four additional times.
Following Soft Start the compressor will transition to steady state operation, and the evaporator fans will start.
If Soft Start is not required, the buzzer will be energized for five seconds the compressor will start and the evapora-
tor fans will start.
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