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

Analyse the refrigeration cycle with the air of the Pressure Enthalpy diagram and refrigerant tables 
SAQA US ID UNIT STANDARD TITLE
9457  Analyse the refrigeration cycle with the air of the Pressure Enthalpy diagram and refrigerant tables 
ORIGINATOR
SGB Air-conditioning Refrigeration and Ventilation 
PRIMARY OR DELEGATED QUALITY ASSURANCE FUNCTIONARY
-  
FIELD SUBFIELD
Field 06 - Manufacturing, Engineering and Technology Engineering and Related Design 
ABET BAND UNIT STANDARD TYPE PRE-2009 NQF LEVEL NQF LEVEL CREDITS
Undefined  Regular  Level 5  Level TBA: Pre-2009 was L5 
REGISTRATION STATUS REGISTRATION START DATE REGISTRATION END DATE SAQA DECISION NUMBER
Passed the End Date -
Status was "Registered" 
2001-06-13  2004-06-13  SAQA 0836/01 
LAST DATE FOR ENROLMENT LAST DATE FOR ACHIEVEMENT
2005-06-13   2008-06-13  

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 does not replace any other unit standard and is not replaced by any other unit standard. 

PURPOSE OF THE UNIT STANDARD 
Plot the thermodynamic cycle of single and multi stage refrigeration systems on a pressure-enthalpy diagram to determine the operating parameters of the system and detect possible reasons for inefficient or ineffective performance of the system. 

LEARNING ASSUMED TO BE IN PLACE AND RECOGNITION OF PRIOR LEARNING 
An understanding the operation of vapour compression refrigeration systems
Convert operating parameters from the imperial or metric system to the SI system or vice versa. 

UNIT STANDARD RANGE 
Single and two stage plants including those incorporating economisers and/or liquid/suction line heat exchangers. 

Specific Outcomes and Assessment Criteria: 

SPECIFIC OUTCOME 1 
Obtain all information required. 

ASSESSMENT CRITERIA
 

ASSESSMENT CRITERION 1 
1. Information required is obtained or requested. 

ASSESSMENT CRITERION 2 
2. Observations are acceptable. 

ASSESSMENT CRITERION 3 
3. Information is in the correct SI units or converted correctly. 

ASSESSMENT CRITERION 4 
4. The correct SI symbols and units are used. 

ASSESSMENT CRITERION 5 
5. The consequences of inaccurate readings or faulty conversions are listed and explained. 

SPECIFIC OUTCOME 2 
Plot the refrigeration cycle on the Pressure-Enthalpy diagram and determine refrigerant properties. 

ASSESSMENT CRITERIA
 

ASSESSMENT CRITERION 1 
1. The pressure-enthalpy diagram for the correct refrigerant in the correct units is selected. 

ASSESSMENT CRITERION 2 
2. All parameters are plotted correctly. 

ASSESSMENT CRITERION 3 
3. The refrigerant properties are determined correctly from the diagram or tables. 

ASSESSMENT CRITERION 4 
4. The correct SI units and symbols are used. 

SPECIFIC OUTCOME 3 
Analyse the refrigeration cycle. 

ASSESSMENT CRITERIA
 

ASSESSMENT CRITERION 1 
1. The enthalpy differences in the components are determined correctly. 
ASSESSMENT CRITERION RANGE 
Refrigerating effect, heat of compression and heat rejection.
 

ASSESSMENT CRITERION 2 
2. The system operation is analysed correctly and the values obtained are compared with accepted norms. 
ASSESSMENT CRITERION RANGE 
Superheat, sub cooling, co-efficient of performance, compressor efficiency, compression ratio.
 

ASSESSMENT CRITERION 3 
3. The effects of including an economiser or a heat exchanger on the performance of the plant are explained. 

ASSESSMENT CRITERION 4 
4. The effects of varying operating parameters on equipment selection on plant performance are explained. 
ASSESSMENT CRITERION NOTES 
Increase or decrease in suction and discharge pressure, over sizing or under sizing of components or accessories, increasing or decreasing evaporator or condenser approach, increasing or decreasing the fluid quantities through the condenser or the evaporator, over or undercharge of refrigerant, inclusion of an economiser and/or a liquid/suction line heat exchanger. 

ASSESSMENT CRITERION 5 
5. The effect of refrigerant glide are explained and discussed. 

SPECIFIC OUTCOME 4 
Calculate the heat balance of the system. 

ASSESSMENT CRITERIA
 

ASSESSMENT CRITERION 1 
1. The refrigerant mass flow and volume flow are determined correctly. 

ASSESSMENT CRITERION 2 
2. The capacities and operating parameters of the components are determined correctly. 
ASSESSMENT CRITERION RANGE 
Capacity of evaporator, TEV, condenser and compressor.
 

ASSESSMENT CRITERION 3 
3. The power input into the system is calculated. 
ASSESSMENT CRITERION RANGE 
Input to motor, gearbox and compressor.
 

ASSESSMENT CRITERION 4 
4. The heat balance of the system is calculated and evaluated. 

ASSESSMENT CRITERION 5 
5. Possible reasons for an unacceptable heat balance are explained. 

ASSESSMENT CRITERION 6 
6. The system performance is explained and discussed. 

SPECIFIC OUTCOME 5 
Evaluate the performance of the plant. 

ASSESSMENT CRITERIA
 

ASSESSMENT CRITERION 1 
1. Acceptability of all operating parameters are evaluated and discussed. 

ASSESSMENT CRITERION 2 
2. Possible reasons for ineffective plant performance are listed and explained. 

ASSESSMENT CRITERION 3 
3. Recommendations that improve plant performance are given. 


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 air-conditioning or refrigeration. 

UNIT STANDARD ESSENTIAL EMBEDDED KNOWLEDGE 
The operation of single and two stage refrigeration systems
The consequences of ineffective plant performance 


Critical Cross-field Outcomes (CCFO): 

UNIT STANDARD CCFO IDENTIFYING 
Identify and solve problems
  • Nature and extent of deviation from specified performance is diagnosed
  • Possible malfunctions are determined 

  • UNIT STANDARD CCFO COLLECTING 
    Collect, analyse, organise and critically evaluate information
  • Critically analyse all operating parameters for correctness and possible deviation from the norms 

  • UNIT STANDARD CCFO SCIENCE 
    Use science and technology effectively and critically
  • By understanding the processes involved 

  • UNIT STANDARD NOTES 
    Assessment of this unit standard could be in the form of a written test. 

    QUALIFICATIONS UTILISING THIS UNIT STANDARD: 
      ID QUALIFICATION TITLE PRE-2009 NQF LEVEL NQF LEVEL STATUS END DATE PRIMARY OR DELEGATED QA FUNCTIONARY
    Core  20722   National Diploma: Air Conditioning, Refrigeration and Ventilation  Level 5  Level TBA: Pre-2009 was L5  Passed the End Date -
    Status was "Registered" 
    2004-06-13  MERSETA 


    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.
     
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    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.