Secondary Controllers in Refrigeration Systems


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.


  1. Trainer from the ADF practical series for the training of mechatronics engineers for refrigeration
  2. refrigeration system with different secondary controllers: evaporation pressure controller KVP, capacity controller KVC, condensation pressure controller KVR, pressure-controlled water valve WVFX as condensation pressure controller, receiver pressure controller KVD, start-up controller KVL
  3. 2 refrigeration chambers: refrigeration and freezing stage
  4. Evaporator selectable via solenoid valves
  5. Adjustable electric heater in the refrigeration chambers as cooling load
  6. Water-cooled coaxial condenser
  7. Pressure measurement at all relevant points in the system
  8. Refrigerant R134a, GWP: 1430

Technical Details

  1. Compressor
  2. Refrigeration capacity: 990W at 5/40°C
  3. Power consumption: 690W at 5/40°C
  4. Cooling load: 0…500W
  5. Receiver: 1,2 L
  6. Refrigerant
  7. R134a
  8. GWP:1430
  9. Filling volume: 1,8 kg

Measuring ranges:

  • Pressure: 5x -1…9bar / 3x -1…24bar
  • Flow rate: 20…250L/h (water) 1…11,5L/h, 2…27L/h (refrigerant)
  • Temperature: -50…300°C


  • 230V, 50Hz, 1 phase
  • 230V, 60Hz, 1 phase; 120V, 60Hz, 1 phase