So-called secondary controllers are used to ensure the optimum operation of large, complex refrigeration systems. They control the evaporation pressure (KVP), the intake pressure of the compressor (KVL), the delivery capacity of the compressor (KVC), the condensation pressure (WVFX, KVR) and the receiver pressure (KVD, NRD).
  With this trainer the student can try out the operation of the different secondary controllers. The secondary controllers can be disabled as required by bypassing or blocking. This option can be used for fault finding. By adjusting the secondary controllers the effect on the overall system can be studied.
  Manometers at all important locations and a manual thermometer enable the monitoring of the system state. The two evaporators for the cooling and freezing stage can be selected via solenoid valves. With an adjustable electrical heater in the refrigeration chamber the effect of a changing cooling load on the secondary controllers can be examined.
  The well-structured instructional material sets out the fundamentals and provides a step-by-step guide through the experiments.

- properties and application options of different

  secondary controllers
  * evaporation pressure controller (KVP)
  * start-up controller (compressor intake control;

    KVL)
  * capacity controller (control of the compressor

    delivery capacity; KVC)
  * condensation pressure controller (WVFX, KVR)
  * receiver pressure controller (KVD with NRD)
- adjustment of optimum operating points
- fault finding in secondary controllers