SMART REEFER 4 (SR-4) Control System

    Caution
  • Risk of Injury
  • Do not operate the SR-4 Controller until you are completely familiar with its function.

The SR-4 is a microprocessor control system designed for a transport refrigeration system. The SR-4 integrates the following functions:

  • Changing setpoint and operating mode

  • Viewing gauge, sensor, and hourmeter readings

  • Initiating Defrost cycles

  • Viewing and clearing alarms

The microprocessor components are located inside the control box, which is located inside the lower roadside service door. The microprocessor is connected to a Human Machine Interface (HMI) Control Panel. It is used to operate the unit. The HMI control panel is mounted on the face of the control box. It is clearly visible through an opening in the lower roadside service door.

See Operating Instructions for more information about the SR-4 Controller.

Depending on the air temperature in the trailer, as sensed by the microprocessor Base Controller, the unit will typically operate in one of the following modes:

Parent topic: Unit Description

Diesel Operation

In diesel operation, the microprocessor will select the operating mode from the following:

  • High Speed Cool

  • Low Speed Cool

  • Low Speed Modulated Cool

  • Null (CYCLE-SENTRY operation only)

  • Low Speed Modulated Heat

  • Low Speed Heat

  • High Speed Heat

  • Defrost

Electric Operation

In electric operation, the microprocessor will select the operating mode from the following:

  • Cool

  • Modulated Cool

  • Null (CYCLE-SENTRY operation only)

  • Modulated Heat (Hot Gas only)

  • Hot Gas Heat

  • Full Heat (Hot Gas and Electric Heat)

  • Defrost (Hot Gas and Electric Heat)

Defrost

Frost gradually builds-up on evaporator coils as a result of normal operation. The unit uses hot refrigerant to defrost the evaporator coils. Hot refrigerant gas passes through the evaporator coil and melts the frost. The water flows through collection drain tubes onto the ground. The methods of Defrost initiation are Automatic and Manual.

Automatic Defrost:The SR-4 automatically initiates timed or demand defrost cycles. The SR-4 microprocessor can be programmed to initiate timed defrost cycles at intervals of 2, 4, 6, 8, or 12 hours. Demand defrost cycles occur if the differences between the return air temperature, discharge air temperature, and coil temperature exceed certain limits. The unit can enter defrost cycles as often as every 30 minutes if required.

Manual Defrost: In Manual Defrost Mode, the operator initiates a defrost cycle. See “Initiating a Manual Defrost Cycle”.

Note The unit will not perform a Manual Defrost cycle unless the unit has been turned on with the ON key, the unit is running in Continuous or CYCLE-SENTRY mode (or shut down in CYCLE-SENTRY Null mode), and the coil temperature is below 45 F (7 C).