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

Design air distribution systems for air-conditioning and ventilation systems 
SAQA US ID UNIT STANDARD TITLE
9447  Design air distribution systems for air-conditioning and ventilation systems 
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  10 
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 
  • Determine the dimensions of circular and rectangular ducting used to convey air for air-conditioning, refrigeration and ventilation systems.
  • Make a ducting layout, recommending construction methods and select the commonly used air terminals and accessories required for draft-free air distribution and balancing.
  • Determine the pressure loss in a system. 
    		•

    LEARNING ASSUMED TO BE IN PLACE AND RECOGNITION OF PRIOR LEARNING 
    Carry out elementary airflow calculations and measurements. Interpret architectural air-conditioning and ventilation layout drawings and sketches. 

    UNIT STANDARD RANGE 
    Low, medium and high-pressure systems, as applied to air-conditioning and ventilation systems. 

    Specific Outcomes and Assessment Criteria: 

    SPECIFIC OUTCOME 1 
    List and explain the factors to be considered when selecting duct sizes. 

    ASSESSMENT CRITERIA     

    ASSESSMENT CRITERION 1 
    1. The factors to be considered in sizing air ducts are listed and explained. 
    ASSESSMENT CRITERION RANGE 
    Space availability, first cost, running cost, sound level, heat gain/loss and leakage losses, aspect ratio, shape, external and internal insulation (lining).
     

    ASSESSMENT CRITERION 2 
    2. The factors used to classify air duct systems are listed and discussed. 

    ASSESSMENT CRITERION 3 
    3. The commonly used duct construction standards are named and discussed. 

    ASSESSMENT CRITERION 4 
    4. The materials used to fabricate ducts are named and advantages and disadvantages are discussed. 

    ASSESSMENT CRITERION 5 
    5. Commonly used duct and fitting construction methods are listed and discussed. 

    ASSESSMENT CRITERION 6 
    6. The effect of the design parameters on the pressure loss is explained. 
    ASSESSMENT CRITERION RANGE 
    Roughness factor, aspect ratio, circumference, length, area, density.
     

    ASSESSMENT CRITERION 7 
    7. The effect of increasing or decreasing volume flow on the pressure loss is explained. 

    ASSESSMENT CRITERION 8 
    8. The effect of transformations and fittings on the pressure loss is explained. 

    SPECIFIC OUTCOME 2 
    Size ducting to convey air. 

    ASSESSMENT CRITERIA     

    ASSESSMENT CRITERION 1 
    1. The different duct sizing methods are named compared and contrasted. 
    ASSESSMENT CRITERION RANGE 
    Static regain and equal friction methods.
     

    ASSESSMENT CRITERION 2 
    2. Initial duct velocity selected is suitable for the type of application. 

    ASSESSMENT CRITERION 3 
    3. All duct sections are sized according to the equal friction method and the static regain method. 

    ASSESSMENT CRITERION 4 
    4. The duct layout is suitable and ducts fit in available space. 

    ASSESSMENT CRITERION 5 
    5. All duct sizes are suitable for joining to branches and outlets/terminals. 

    ASSESSMENT CRITERION 6 
    6. The advantages and disadvantages of the static regain method and the equal friction method are stated and discussed. 

    SPECIFIC OUTCOME 3 
    Select the air terminals. 

    ASSESSMENT CRITERIA     

    ASSESSMENT CRITERION 1 
    1. Selection factors for the supply and return air outlets are determined correctly. 
    ASSESSMENT CRITERION RANGE 
    Air movement in the space, type, dimensions, throw, drop/rise, pressure loss, noise level.
     

    ASSESSMENT CRITERION 2 
    2. All air terminals are selected correctly. 

    ASSESSMENT CRITERION 3 
    3. Applications and limitations of flexible ducting are named and discussed. 

    ASSESSMENT CRITERION 4 
    4. Consequences of faulty selection are elaborated on. 

    ASSESSMENT CRITERION 5 
    5. Actual operating parameters are determined correctly. 

    ASSESSMENT CRITERION 6 
    6. Deviations from specifications are listed and discussed. 

    ASSESSMENT CRITERION 7 
    7. Positions and types of air balancing devices are selected correctly. 

    SPECIFIC OUTCOME 4 
    Calculate the pressure loss in the system. 

    ASSESSMENT CRITERIA     

    ASSESSMENT CRITERION 1 
    1. All pressure losses in the system are calculated or determined correctly. 
    ASSESSMENT CRITERION RANGE 
    Losses in ducting, fittings, air terminals, accessories and equipment
     

    ASSESSMENT CRITERION 2 
    2. The pressure loss in the entire system is determined correctly. 

    SPECIFIC OUTCOME 5 
    Specify the fan duty. 

    ASSESSMENT CRITERIA     

    ASSESSMENT CRITERION 1 
    1. The fan pressures required are correctly specified. 
    ASSESSMENT CRITERION RANGE 
    Fan static, velocity and total pressures.
     

    ASSESSMENT CRITERION 2 
    2. The fan volume is correctly specified. 

    ASSESSMENT CRITERION 3 
    3. The fan operating density is correctly specified. 

    ASSESSMENT CRITERION 4 
    4. The fan power requirements are correctly specified. 

    SPECIFIC OUTCOME 6 
    Write a specification. 

    ASSESSMENT CRITERIA     

    ASSESSMENT CRITERION 1 
    1. Ducting sizes and construction methods are correctly specified. 

    ASSESSMENT CRITERION 2 
    2. Air terminals are correctly specified. 

    ASSESSMENT CRITERION 3 
    3. All accessories are correctly specified. 

    ASSESSMENT CRITERION 4 
    4. The fan duty is correctly specified. 


    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 
    Names, functions and characteristics of air distribution equipment and accessories
    Implications of selecting unsuitable operating parameters for air distribution equipment and accessories
    The importance of correct air distribution in air-conditioning applications
    The effect of selection of equipment on the first and running cost of the plant 


    Critical Cross-field Outcomes (CCFO): 

    UNIT STANDARD CCFO IDENTIFYING 
    Identify and solve problems
  • Interpret drawings in order to obtain information required to solve problems and carry out tasks.
  • Determine positions of air outlets and air return grilles. 
    		•

    UNIT STANDARD CCFO COLLECTING 
    Collect, analyze, organize and critically evaluate information
  • Interpreting manufacturer`s specifications and instructions.
  • Interpret graphs and tables. 
    		•

    UNIT STANDARD CCFO SCIENCE 
    Use science and technology effectively and critically
  • Selecting the correct air distribution method and system. 
    		•

    UNIT STANDARD CCFO DEMONSTRATING 
    Demonstrate an understanding of the world as a set of related systems.
  • Be aware of the effect of air movement on human comfort. 
    		•

    UNIT STANDARD NOTES 
    On assessment the learner must be provided with all the drawing and catalogues required.
    Manual or computer-aided sizing methods may be used.
    Industry standards for design parameters shall be applied. 

    QUALIFICATIONS UTILISING THIS UNIT STANDARD: 
      ID QUALIFICATION TITLE PRE-2009 NQF LEVEL NQF LEVEL STATUS END DATE PRIMARY OR DELEGATED QA FUNCTIONARY
    Elective  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.