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

Select refrigerant pipe sizes, plan piping layout and determine system pressure losses 
SAQA US ID UNIT STANDARD TITLE
9404  Select refrigerant pipe sizes, plan piping layout and determine system pressure losses 
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  5 
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 
Select refrigerant pipe sizes for refrigeration systems in which the oil is carried throughout the circuit with the refrigerant and ensure that the oil is returned to the compressor and determine system pressure losses and saturation temperatures in evaporator and condenser. 

LEARNING ASSUMED TO BE IN PLACE AND RECOGNITION OF PRIOR LEARNING 
Explain the operation of the vapour compression refrigeration system and the function of system components and accessories. 

UNIT STANDARD RANGE 
Select the pipe sizes from tables or graphs, which contain information about refrigerant type, kW refrigeration carrying capacity, refrigerant velocity, operating pressures and pressure drop. 

Specific Outcomes and Assessment Criteria: 

SPECIFIC OUTCOME 1 
Select pipe sizes for system with single, variable capacity compressor, single condenser. 
OUTCOME NOTES 
Select the refrigerant pipe sizes for a system with a single, variable capacity compressor, a single condenser and a single dry expansion evaporator with a single metering device. 

ASSESSMENT CRITERIA 

ASSESSMENT CRITERION 1 
1. Pipe sizes are chosen that ensure that the capacity of the system is not unnecessarily adversely affected, at any load condition. 

ASSESSMENT CRITERION 2 
2. The recommended pipe pressure losses are adhered to. 

ASSESSMENT CRITERION 3 
3. Pipe sizes are chosen that ensure quiet operation during all load conditions. 

ASSESSMENT CRITERION 4 
4. The piping layout design prevents vibration from being transmitted throughout the system. 

ASSESSMENT CRITERION 5 
5. The design eliminates the torque effect of the compressor at start-up from breaking the pipes. 

ASSESSMENT CRITERION 6 
6. The consequences of over sizing or under sizing the pipes are listed and explained. 

ASSESSMENT CRITERION 7 
7. The consequences of pipe vibration are listed and explained. 

ASSESSMENT CRITERION 8 
8. Methods of vibration elimination are listed and explained. 

SPECIFIC OUTCOME 2 
Select pipe sizes for circuit with interconnected multiple, variable capacity compressors. 
OUTCOME NOTES 
Select the refrigerant pipe sizes for a circuit with interconnected multiple, variable capacity compressors, with interconnected multiple condensers and interconnected multiple dry expansion evaporators, each with its own metering device. 

ASSESSMENT CRITERIA 

ASSESSMENT CRITERION 1 
1. Pipe sizes are selected that ensure that the capacity of the system is not unnecessarily adversely affected, at any load condition. 

ASSESSMENT CRITERION 2 
2. Pipe sizes are chosen that ensure quiet operation during all load conditions. 

ASSESSMENT CRITERION 3 
3. The piping layout prevents vibration from being transmitted throughout the system. 

ASSESSMENT CRITERION 4 
4. The layout eliminates the torque effect of the compressors at start-up from breaking the pipes. 

ASSESSMENT CRITERION 5 
5. The layout ensures that no hot gas is forced into the liquid line at any stage of the cycle's operation. 

ASSESSMENT CRITERION 6 
6. The design ensures that the refrigerant and oil return to the compressor and the operation of active evaporators are not affected by some evaporators being in the off-cycle. 

SPECIFIC OUTCOME 3 
Select refrigerant pipe sizes to ensure adequate oil return. 

ASSESSMENT CRITERIA 

ASSESSMENT CRITERION 1 
1. Pipe sizes are selected that ensure the oil is carried with the refrigerant in the vapour phase. 

ASSESSMENT CRITERION 2 
2. Vertical risers are designed that ensure the oil is carried back to the compressors with the refrigerant at all load conditions. 

ASSESSMENT CRITERION 3 
3. Pipe layout is designed to ensure that no oil is able to run back to the compressors' heads during the off-cycle. 

ASSESSMENT CRITERION 4 
4. Pipe layout is designed to ensure that no oil is able to return to the compressor as slugs at any time in the running cycle. 

ASSESSMENT CRITERION 5 
5. The layout ensures that the oil level in both compressors remains at the correct level during all load conditions. 

ASSESSMENT CRITERION 6 
6. Consequences of ignoring oil return problems are named and discussed. 

SPECIFIC OUTCOME 4 
Select required accessories to ensure safe operation & proper refrigerant distribution and control. 
OUTCOME NOTES 
Select the required accessories to ensure safe operation and proper refrigerant distribution and control. 

ASSESSMENT CRITERIA 

ASSESSMENT CRITERION 1 
1. All accessories to ensure safe operation are listed and discussed. 

ASSESSMENT CRITERION 2 
2. All accessories required for proper refrigerant distribution are listed and discussed. 

ASSESSMENT CRITERION 3 
3. All accessories required for refrigerant control are listed and discussed. 

ASSESSMENT CRITERION 4 
4. All accessories required ensuring safe operation, proper refrigerant distribution and control are selected correctly. 
ASSESSMENT CRITERION RANGE 
Metering device, distributor, accumulator, solenoid valve, shut-off valves, and oil separators.
 

ASSESSMENT CRITERION 5 
5. The circumstances when the various accessories are required are listed, explained and discussed. 

SPECIFIC OUTCOME 5 
Plan the refrigerant piping layout ensuring oil return and minimal pressure loss. 

ASSESSMENT CRITERIA 

ASSESSMENT CRITERION 1 
1. The number of bends and other fittings is kept to a minimum. 

ASSESSMENT CRITERION 2 
2. All accessories for service requirements and proper operation are included. 

ASSESSMENT CRITERION 3 
3. All piping is sloped in the direction of the flow of refrigerant. 

ASSESSMENT CRITERION 4 
4. Pipe risers are checked for oil return. 

ASSESSMENT CRITERION 5 
5. Double risers are selected if required. 

SPECIFIC OUTCOME 6 
Make a sketch of the piping layout and write a specification. 

ASSESSMENT CRITERIA 

ASSESSMENT CRITERION 1 
1. A clear sketch of the layout is made. 

ASSESSMENT CRITERION 2 
2. All accessories and fittings are shown and are in the correct location. 

ASSESSMENT CRITERION 3 
3. All bracketing and spacing required is indicated. 

ASSESSMENT CRITERION 4 
4. The insulation required is specified. 

ASSESSMENT CRITERION 5 
5. The accessories required are specified. 

ASSESSMENT CRITERION 6 
6. The types and sizes of pipes are indicated. 

ASSESSMENT CRITERION 7 
7. A clear specification is written. 

SPECIFIC OUTCOME 7 
Determine the system pressure losses. 

ASSESSMENT CRITERIA 

ASSESSMENT CRITERION 1 
1. The pressure losses in the piping are determined correctly. 

ASSESSMENT CRITERION 2 
2. The pressure losses in the components and accessories are determined correctly. 

ASSESSMENT CRITERION 3 
3. The pressure losses are expressed as a temperature difference and in kilopascal. 

ASSESSMENT CRITERION 4 
4. The evaporating and condensing temperatures are determined correctly. 


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 
Importance of selecting the correct pipe sizes to ensure efficient and effective operation.
Refrigeration capacity may need to be sacrificed in favour of vapour velocity to entrain oil.
The necessity of accessories and correct piping layout to ensure safe operation. 


Critical Cross-field Outcomes (CCFO): 

UNIT STANDARD CCFO IDENTIFYING 
Identify and solve problems
  • Selection of pipe sizes and accessories 
    		•

    UNIT STANDARD CCFO COLLECTING 
    Collect, analyse, organise and critically evaluate information
  • Determine pipe sizes and types of accessories 
    		•

    UNIT STANDARD CCFO SCIENCE 
    Use science and technology effectively and critically
  • Use of tables and graphs 
    		•

    UNIT STANDARD NOTES 
    Pipe sizing charts or tables must be made available. 

    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.
     
    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.