Evidence shall show that knowledge has been acquired of safe working practices and diagnosing and rectifying faults in complex refrigeration/air conditioning systems. All knowledge and skills detailed in this unit should be contextualised to current industry practices and technologies. KS01-EJ112A Complex refrigeration and air conditioning system fault finding and repair Evidence shall show an understanding of fault finding and repairing complex refrigeration and air conditioning system, applying safe working practices and relevant Standards, Codes and Regulations to an extent indicated by the following aspects: T1 Fault finding techniques Factors to consider in clarifying the nature of a fault encompassing: initial fault report confirmation of symptoms of the fault comparison of symptoms with normal operation Effect to cause reasoning — assumptions of possible causes Methods for testing assumptions encompassing: Visual inspection Sectional testing Split-half tests Component isolation Dealing with intermittent faults Note: Typical causes of intermittent faults are vibration, shock, changes in temperature and electromagnetic interference. T2 Refrigeration system analysis Pressure Enthalpy definitions high pressure & low pressure refrigerants triple point of new refrigerants glide of trinary blends differential evaporation of refrigerant blends variable refrigerant volume Refrigeration cycle expansion process vaporising process compression process condensing process compression ratio Enthalpy processes co-efficient of performance effect of suction temperature on cycle efficiency effect of condensing temperature on cycle efficiency Actual refrigerating cycles design operating conditions effects of superheating suction vapour superheating without useful cooling superheating that produces useful cooling superheating in suction piping outside the refrigerated space superheating the vapour inside the refrigerated space effects of subcooling the liquid effects liquid - suction heat exchangers effects of pressure losses resulting from friction Refrigeration cycle faults symptoms and causes measurements and fault confirmation tests T3 Air conditioning system analysis Psychrometric chart properties, definitions and units plotting conditions RA, SA, OA, MA Psychometric processes heating cooling only cooling and dehumidification cooling , dehumidification and reheat Design operating conditions indoor and outdoor wet and dry bulb temperatures volume flow rate supply, return and outdoor air Air conditioning system faults symptoms and causes measurements and fault confirmation tests T4 Power and control system analysis power and control circuit diagrams sequence of operation manufacturers diagrams, specifications and instructions power and control circuit faults symptoms and causes measurements and fault confirmation tests |