COOL Mode

TM 10-4110-262-13&P

0003 00

COOL Mode

When 230 volt three phase power is applied to the unit power plug, power is available at the CMC

COOL contactor and the CMC HEAT contactor. Power also flows through the primary of the

transformer. 24 volt AC power is then produced by the transformer secondary that flows to the bridge

rectifier. The rectifier converts the AC voltage to DC voltage that is filtered by capacitor C1. 115-volt

power is also available from the transformer through fuses 6 and 7 to the lamp connection to power the

light inside the container.

The transformer secondary is also connected to diodes D1 and D2. DC voltage from these diodes is

filtered by capacitor C2. 24 volt DC power flows through fuse 4 to the controller through the red wire to

pin 2 of connector C-9 in the back of the controller.

When the controller is turned on the display will show the temperature inside the container. If the

temperature inside the container is above the set point on the controller by more than 3 degrees F the

controller output to pin 6 of connector C-9 will apply power to the blue wire which will then pass power to

wire 7 to the high pressure cutout pressure switch (HPCO) and on through the low pressure cutout

pressure switch (LPCO) to the power relay.

With the power relay closed power will flow from the bridge rectifier through 2R to the normally closed

contacts of relays CR1 and CR2, fuse 3, the contacts of the power relay (PR), the normally closed contact

of the ER relay to the compressor motor contactor (CMC COOL). This contactor coil goes to ground

through the motor protector (TH). This will cause the motor contactor to energize allowing power to flow

through its contacts to the compressor motor. If the motor overheats for any reason the motor protector

will open the grounding circuit of the contactor coil turning off power to the compressor until the

compressor cools.

When the compressor contactor energizes power also flows through its auxiliary contacts from circuit 2RC

to the K4 relay. This relay will then close a circuit from 2RB to 9A to a transistor on the PC board that

allows the evaporator fan relay (EFR) to close. Power will then flow from relays CR1 and CR2 through

the EFR contacts and fuses 1 and 2 to the evaporator fan motors.

Power will also flow from the power relay through the normally closed contacts of the defrost relay (D) to

the condenser fan. In addition power is also supplied to the drain tube heaters from the power relay.

These heaters are used to prevent the condensate tubes from freezing shut.

NULL Mode

If the temperature inside the container is at or within 4 degrees above the set point, the output of the

controller to pin 6 of connector C-9 is turned off. This will shut off the compressor, the drain tube heaters

and the condenser and evaporator fans.

HEAT Mode

If the temperature inside the container is 4 lower than the set point on the controller power to the blue

wire at pin 6 of connector C-9 is shut off, but power is now available to pin 10 and the orange wire to the

heat contactor (CMC HEAT). This will cause the contacts of this contactor to close allowing power to flow

to the electric heating elements. The auxiliary contacts of this contactor also connect circuit 9B which is

connected to 2RC to 9D energizing relay K4 which turns on the evaporator motors as described above.

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