DESCRIPTION

Technical Description

The control of refrigeration units such as chiller cabinets, refrigerated display cases and freezers is a key topic in commercial refrigeration. The control aims at safeguarding a high level of food quality with simultaneous energy-efficient operation.

With ET 930 the operation and programming of an industrial evaporator controller (refrigeration controller) is taught in the example of a freezer. Software simulates the freezer. The schematic depicted on the front panel aids comprehension. Lamps in the schematic indicate the operating state of the individual components.

The refrigeration controller controls the temperature of the freezer via the electronic expansion valve. It also controls the air circulation fan. It provides for the defrosting of the evaporator and prevents the freezing of the freezer lid by way of a frame heating. The refrigeration controller continuously monitors the operation of the components and issues an alarm signal should errors occur.

The controller is programmed via a data cable using a programming device. This allows for adjustments of the thermostat function, daytime/night-time operation, the defrosting function, energy saving functions and safety functions. 

In the simulation software the outside temperature is entered, the refrigerant selected and the door of the freezer opened or closed. In the "time graph" menu, the operating states of the individual components are displayed and the temperature and pressure graphs recorded.

Additional real components, such as expansion valve and pressure and temperature sensors, are used for demonstration purposes and increase the practical relevance.

The well-structured instructional material sets out the fundamentals and provides a step-by-step guide through the experiments.

Learning Objectives / Experiments

- modern refrigeration controller with electronic expansion valve
- functional principle of the controller 
  * thermostat function  
  * daytime and night-time operation
  * operation with open and closed freezer
  * defrost functions
  * safety functions
  * alarm functions
  * monitoring of the components
- controller programming
- fault finding