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ET 174


Technical Description

Identifying electrical faults in air conditioning systems requires comprehensive knowledge. This knowledge includes the design and operation of the individual electrical components as well as the reading of circuit diagrams. ET 174 helps to acquire this knowledge. 

ET 174 demonstrates the electrical circuit of a complex full conditioning system with heat pump function. The control circuits are actually present. The components in the load circuits are simulated (e.g. compressor, heater, 4-way reversing valve). 

The air conditioning system with heat pump function cools in the summer and heats in the winter. During heating operation the defrost timer introduces a hot gas defrosting by briefly switching the 4-way reversing valve. At very low outer temperatures an electrical auxiliary heating is activated during heating operation. With low air humidity the hygrostat activates the humidifying function.

Typical protection devices, such as circuit breaker and frost protection monitor, complete the electrical circuit. The operating state of the simulated components is indicated via lamps in the circuit diagram on the front panel. 

The simulation of 30 different faults, such as coil fracture in the motor or faulty relays, is possible. For fault identification the voltages or resistances at the lab jacks are checked with the multimeter. The depiction of the circuit diagram on the front panel facilitates the allocation of the measuring points.

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

Learning Objectives / Experiments

- electrical design and operation of full conditioning systems
- reading and understanding electrical circuit diagrams
- design and operation of electrical components in an air conditioning system
  * start-up capacitor
  * start-up relay
  * operating capacitor
  * overheat protection
  * Heinemann circuit breaker
  * solenoid valve
  * defrost timer
  * float switch
  * thermostat
  * hygrostat
  * frost protection monitor
- fault finding in electrical components
  * in idle state
  * under mains voltage


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