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SOUTH AFRICAN QUALIFICATIONS AUTHORITY 
REGISTERED UNIT STANDARD THAT HAS PASSED THE END DATE: 

Interpret the effect of operating conditions on components, safety and control devices 
SAQA US ID UNIT STANDARD TITLE
262178  Interpret the effect of operating conditions on components, safety and control devices 
ORIGINATOR
SGB Air-conditioning Refrigeration and Ventilation 
PRIMARY OR DELEGATED QUALITY ASSURANCE FUNCTIONARY
-  
FIELD SUBFIELD
Field 06 - Manufacturing, Engineering and Technology Manufacturing and Assembly 
ABET BAND UNIT STANDARD TYPE PRE-2009 NQF LEVEL NQF LEVEL CREDITS
Undefined  Regular  Level 4  NQF Level 04  6 
REGISTRATION STATUS REGISTRATION START DATE REGISTRATION END DATE SAQA DECISION NUMBER
Passed the End Date -
Status was "Reregistered" 		 2018-07-01  2023-06-30  SAQA 06120/18 
LAST DATE FOR ENROLMENT LAST DATE FOR ACHIEVEMENT
2024-06-30   2027-06-30  

In all of the tables in this document, both the pre-2009 NQF Level and the NQF Level is shown. In the text (purpose statements, qualification rules, etc), any references to NQF Levels are to the pre-2009 levels unless specifically stated otherwise.  

This unit standard replaces: 
US ID Unit Standard Title Pre-2009 NQF Level NQF Level Credits Replacement Status
116709  Explain the operation of the vapour compression refrigeration cycle, and identify and explain the operation of the components and the associated controls, safety devices and defrost systems  Level 3  NQF Level 03  10   

PURPOSE OF THE UNIT STANDARD 
People credited with this unit standard have proven the ability to:
  • Explain the operation of an actual vapour compression refrigeration cycle as applied to direct expansion, flooded, liquid overfeed and reverse cycle systems and Identify and explain the function of the components and the associated controls, safety devices and defrost systems.
  • Give advantages and limitations of direct expansion flooded, liquid overfeed and reverse cycle systems.
  • Discuss applications of the various systems.
  • State principles of operation and internal and external factors affecting the operation and performance of refrigeration components and accessories in an actual vapour compression refrigeration system. 
    		•

    LEARNING ASSUMED TO BE IN PLACE AND RECOGNITION OF PRIOR LEARNING 
    Explaining the operation of the basic vapour compression refrigeration system. 

    UNIT STANDARD RANGE 
    Refrigeration systems and their application:
  • Air-cooled, water-cooled and evaporatively cooled plants of the DX (direct expansion), flooded, liquid overfeed (liquid recirculation) and reverse cycle type (heat pump), as applied to domestic, commercial and industrial systems. Single stage operation only, but including multi-evaporator and condenser systems and liquid circulation systems.

    Refrigerant control devices:
  • Capillary tubes, internally and externally equalised thermostatic expansion valves (with different bulb charges), solenoid type expansion devices, two-way thermostatic expansion valves, expansion devices for heat pumps, refrigerant distributors, hot-gas by-pass valves and cylinder unloaders, reversing valves, solenoid valves, high-pressure and low-pressure float valves, evaporator pressure regulators and crankcase pressure regulators.

    Controls and safety devices:
  • The following controls and safety devices used in refrigeration systems (excluding systems in which ammonia is the refrigerant).
    Manual and auto-reset low pressure and high pressure controls, oil pressure controls, head pressure control systems, temperature controllers (incl. electronic types), temperature sensors, humidistats, flow switches, level switches, rupture discs, pressure relief devices, defrost timers.

    Defrost systems:
  • Off-cycle defrosts, electric defrost and hot gas defrost systems terminated by time and/or temperature and/or pressure. 
    		•

    Specific Outcomes and Assessment Criteria: 

    SPECIFIC OUTCOME 1 
    Explain the effect of actual operating conditions on the performance of the various components in the actual vapour compression cycle. 

    ASSESSMENT CRITERIA     

    ASSESSMENT CRITERION 1 
    The effects of superheat and sub cooling on the operating conditions and the performance of components and accessories in the system are explained. 

    ASSESSMENT CRITERION 2 
    The effect of pipe pressure losses on the operating conditions and the performance of components and accessories in the system is explained. 

    ASSESSMENT CRITERION 3 
    The effect of non-isentropic compression on the operating conditions and the performance of components and accessories in the system is explained. 

    SPECIFIC OUTCOME 2 
    List, identify and state the purpose of refrigerant control devices. 

    ASSESSMENT CRITERIA     

    ASSESSMENT CRITERION 1 
    The various types of refrigerant control devices are listed. 

    ASSESSMENT CRITERION 2 
    The purpose of the refrigerant control devices in a refrigeration system is explained. 

    ASSESSMENT CRITERION 3 
    Typical examples of applications of refrigerant control devices in a refrigeration system are given. 

    ASSESSMENT CRITERION 4 
    The various methods of controlling refrigerant flow in a system are listed. 

    ASSESSMENT CRITERION 5 
    The various refrigerant control devices are correctly identified and their position on a plant indicated. 

    ASSESSMENT CRITERION 6 
    The importance of the correct positioning of the refrigerant control device in the system is explained. 

    ASSESSMENT CRITERION 7 
    The different makes and models of refrigerant control devices are identified. 

    SPECIFIC OUTCOME 3 
    Explain the operation of refrigerant control devices. 

    ASSESSMENT CRITERIA     

    ASSESSMENT CRITERION 1 
    The operation of the various refrigerant control devices and their influence on system performance is explained. 

    ASSESSMENT CRITERION 2 
    Possible faults on refrigerant metering devices during operation are listed and discussed. 

    ASSESSMENT CRITERION 3 
    The required adjustments to be made to the devices to ensure correct control action are explained. 

    ASSESSMENT CRITERION 4 
    The importance of correctly matching the refrigerant control device to the system is explained. 

    ASSESSMENT CRITERION 5 
    Component parts of refrigerant control devices are listed and identified. 

    ASSESSMENT CRITERION 6 
    Installation procedures in accordance with manufacturer`s specifications are explained. 

    SPECIFIC OUTCOME 4 
    List the commonly applied controls and safety devices for refrigeration plants and explain their purpose and operation. 

    ASSESSMENT CRITERIA     

    ASSESSMENT CRITERION 1 
    The commonly used control and safety devices are listed. 

    ASSESSMENT CRITERION 2 
    The purpose of the control devices is stated and discussed. 

    ASSESSMENT CRITERION 3 
    The purpose of the safety devices is stated and discussed. 

    ASSESSMENT CRITERION 4 
    The operation of the control and safety devices is explained. 

    ASSESSMENT CRITERION 5 
    The method of determining the setting of the devices is explained. 

    ASSESSMENT CRITERION 6 
    The importance of selecting the right operating range for the devices is demonstrated and explained. 

    ASSESSMENT CRITERION 7 
    The consequences of faulty selection and/or operation, wrong settings and/or not including safety devices are stated and explained. 

    SPECIFIC OUTCOME 5 
    Identify refrigeration plant control and safety devices. 

    ASSESSMENT CRITERIA     

    ASSESSMENT CRITERION 1 
    Each control device is correctly identified. 

    ASSESSMENT CRITERION 2 
    Each safety device is correctly identified. 

    ASSESSMENT CRITERION 3 
    The difference between and the purposes of control devices and safety devices are explained. 

    SPECIFIC OUTCOME 6 
    List the commonly used defrost systems and explain their purpose and operation. 

    ASSESSMENT CRITERIA     

    ASSESSMENT CRITERION 1 
    The purposes of defrosting coils are listed and explained. 

    ASSESSMENT CRITERION 2 
    The various methods of defrosting coils are listed and their operation explained. 

    ASSESSMENT CRITERION 3 
    The methods of initiating and terminating the defrost cycle are explained. 

    ASSESSMENT CRITERION 4 
    The sequence of events when defrosting coils is explained. 

    ASSESSMENT CRITERION 5 
    The consequences of no, insufficient or extended defrosting are listed and explained. 

    ASSESSMENT CRITERION 6 
    The importance of heater tapes on the drip tray and the drain is stated and discussed. 


    UNIT STANDARD ACCREDITATION AND MODERATION OPTIONS 
  • Any person wishing to be assessed against this unit standard may apply to an assessment agency, assessor or provider institution accredited by the relevant ETQA, who may appoint a moderator to be present at the assessment.
  • The assessor must have knowledge and experience of refrigeration as applied to air conditioning and/or refrigeration plants. 
    		•

    UNIT STANDARD ESSENTIAL EMBEDDED KNOWLEDGE 
  • The names and functions of refrigeration systems, components, controls, safety devices and defrost systems.
  • Types and principle of operation of various actual vapour compression systems.
  • Description of operation of various systems.
  • Various types of vapour compression systems and their application.
  • Consequences of selecting incorrect system for application.
  • Principles of thermodynamics and fluid mechanics. 
    		•

    UNIT STANDARD DEVELOPMENTAL OUTCOME 
    N/A 

    UNIT STANDARD LINKAGES 
    N/A 


    Critical Cross-field Outcomes (CCFO): 

    UNIT STANDARD CCFO IDENTIFYING 
    Identify and solve problems:
  • Select correct refrigeration systems for particular application.
  • Apply thermodynamic principles during design of vapour compression system.
  • Identify different devices. 
    		•

    UNIT STANDARD CCFO SCIENCE 
    Use science and technology effectively and critically:
  • Apply thermodynamic and fluid mechanic principles.
  • Identification of devices and explaining their purpose. 
    		•

    UNIT STANDARD ASSESSOR CRITERIA 
    N/A 

    REREGISTRATION HISTORY 
    As per the SAQA Board decision/s at that time, this unit standard was Reregistered in 2012; 2015. 

    UNIT STANDARD NOTES 
    This unit standard replaces unit standard 116709, "Explain the operation of the vapour compression refrigeration cycle, and identify and explain the operation of the components and the associated controls, safety devices and defrost systems", Level 3, 10 credits. 

    QUALIFICATIONS UTILISING THIS UNIT STANDARD: 
      ID QUALIFICATION TITLE PRE-2009 NQF LEVEL NQF LEVEL STATUS END DATE PRIMARY OR DELEGATED QA FUNCTIONARY
    Core  65509   Further Education and Training Certificate: Air-conditioning, Refrigeration and Ventilation  Level 4  NQF Level 04  Passed the End Date -
    Status was "Reregistered"     		 2023-06-30  MERSETA 
    Elective  67329   National Certificate: Inshore Maritime Operations  Level 3  NQF Level 03  Passed the End Date -
    Status was "Reregistered"     		 2015-06-30  TETA 


    PROVIDERS CURRENTLY ACCREDITED TO OFFER THIS UNIT STANDARD: 
    This information shows the current accreditations (i.e. those not past their accreditation end dates), and is the most complete record available to SAQA as of today. Some Primary or Delegated Quality Assurance Functionaries have a lag in their recording systems for provider accreditation, in turn leading to a lag in notifying SAQA of all the providers that they have accredited to offer qualifications and unit standards, as well as any extensions to accreditation end dates. The relevant Primary or Delegated Quality Assurance Functionary should be notified if a record appears to be missing from here.
     
    NONE 


    All qualifications and part qualifications registered on the National Qualifications Framework are public property. Thus the only payment that can be made for them is for service and reproduction. It is illegal to sell this material for profit. If the material is reproduced or quoted, the South African Qualifications Authority (SAQA) should be acknowledged as the source.