UEE Electrotechnology Training ackage UEEEEJ07A Air conditioning and refrigeration systems, major components and associated Learner Workbook Version Training and Education Support Industry Skills Unit Meadowbank roduct Code: 567
UEEEEJ07A Air conditioning and refrigeration systems, major components and associated Table of Contents Introduction... 5. General Introduction... 5. Using this learner guide... 5 3. rior knowledge and experience... 7 4. Unit of competency overview... 7 5. Assessment... 8 6. Risk Assessment Terminology... 0 Topic : Fans and air distribution... Fans... Air distribution... 3 Air flow... 8 Air filtration... 35 Topic : Cool room and freezer room systems... 39 Food storage and spoilage... 40 Types of rooms and their construction... 43 Components and features... 47 Layout and installation... 5 System and defrost controls... 53 Topic 3: (Commercial) packaged air conditioning systems... 6 Types and applications... 6 System design features... 68 Installation requirements... 7 Control systems... 73 Topic 4: Merchandising and display cabinets... 8 Types of cabinets and construction... 8 Components and features... 85 System and defrost controls... 89 Layout and installation requirements... 93 Multiple systems... 93 TAFE SW (Training & Education Support, Industry Skills Unit Meadowbank) 0
UEEEEJ07A Air conditioning and refrigeration systems, major components and associated Topic 5: Cooling towers and associated... 99 Types, applications and construction... 99 Health and legal requirements...03 Installation requirements...04 Water pumps and condenser water systems...05 Topic 6: Residential air conditioning... 09 Types, applications, construction and operation...09 Regulations and Codes...30 Selection...3 Installation rocedures...38 Resource Evaluation Form... 49 TAFE SW (Training & Education Support, Industry Skills Unit Meadowbank) 0
UEEEEJ07A Air conditioning and refrigeration systems, major components and associated Topic : Fans and air distribution Topics Fans Functions Types Operation Applications Air distribution Introduction Ducting types Components and control devices Duct sizing methods Air flow Measurement Adjustment air balancing Air filtration Functions Types Operation Applications Fans Functions In any refrigeration or air conditioning system a medium is required to be cooled (or heated) to allow heat energy to be transferred to the refrigerant. The most common medium used is air. To enable this to occur, air needs to move over the heat exchanger. Some (smaller) systems simply rely on natural convection but most use fans to move the air. Fans work simply by creating a pressure difference between the inlet and the outlet which causes air movement. There are a variety of fan types used in the refrigeration and air conditioning industry used for a mixture of different requirements, such as: Moving air across an evaporator coil Moving air across a condenser coil Circulating air through ducting TAFE SW (Training & Education Support, Industry Skills Unit Meadowbank) 0 age of 49
UEEEEJ07A Air conditioning and refrigeration systems, major components and associated Ideal applications for them are: Condenser fans Evaporator fans (induced or forced draught coolers) Residential and light commercial exhaust fans (window and ceiling). Activity Using a supplier s catalogue (such as Actrol arts or Heatcraft), research the different pitch angles propeller fan blades are available in. When installing propeller fans, care should be taken that no restrictions or blockages are created that will affect airflow, other than those that a manufacturer has fitted. The least amount of resistance for airflow for these fans will ensure they are working to their maximum efficiency. Axial fans These fan types are similar in design to propeller fans having a centre boss or hub with blades attached. The main difference is in the design of the actual blades. Whilst the blades on propeller fans are shaped like paddles, axial fan blades are shaped in a more aerofoil design allowing them to cut through the air more smoothly. The design of the impeller of an axial fan is adjustable allowing blade angles to be adjusted to any required changes. Axial fans are suitable for moving large quantities of air, although still at relatively low static pressures compared to the air volumes they are capable of moving. Because of their design, they are ideally installed directly in round or square ducting saving on space. The impeller has adjustable blades which make it possible to adapt the fan to the requirement changes. Belt driven axial fans are used in situations where it is important that the motor is kept out of the airstream due to high temperature or the corrosive nature of the gases/fumes involved. Although they efficient in moving air, axial fans can generate higher noise levels than other types. The choice of application s for these fans must be carefully considered. Silencers or attenuators can be installed to minimise the noise. TAFE SW (Training & Education Support, Industry Skills Unit Meadowbank) 0 age 3 of 49
UEEEEJ07A Air conditioning and refrigeration systems, major components and associated There are three (3) common fan laws relating to:. Airflow/fan speed. Air (static) pressure/fan speed 3. ower consumed/fan speed. Fan law : The flow rate varies proportionally to the speed. V V where V original volume flow rate (L/s) V new volume flow rate (L/s) original rotating speed of fan (rpm) new rotating speed of fan (rpm) Fan law : The pressure developed is proportional to the square of the fan speed. where p p original static pressure (a) new static pressure (a) original rotating speed of fan (rpm) new rotating speed of fan (rpm) Fan law 3: The power consumed is proportional to the cube of the fan speed. 3 where original motor power (kw) new motor power (kw) original rotating speed of fan (rpm) new rotating speed of fan (rpm) age 6 of 49 TAFE SW (Training & Education Support, Industry Skills Unit Meadowbank) 0
UEEEEJ07A Air conditioning and refrigeration systems, major components and associated Example: A carpark exhaust system extracts 3,500 litres of air per second from the ventilated space. The motor driving the fan is rated at 7.5 kw and is drawing full load amps. The fan is rotating at 700 rpm. A new standard has been enacted and the system must extract 3,900 litres of air per second. Calculate the new speed of the fan to achieve the required airflow. Calculate the new motor power required. Answer:. The new speed rating of the fan Fan law : V V therefore V V 3900 L/s 700 rpm 3500 L/s 780 rpm. The new motor power consumption Fan law 3: therefore 3 3 7.5 a 700 rpm 780 rpm 0.4 kw TAFE SW (Training & Education Support, Industry Skills Unit Meadowbank) 0 age 7 of 49
UEEEEJ07A Air conditioning and refrigeration systems, major components and associated Answer: ew motor pulley size transpose the formula: n d n d d n d n d 470 rpm 430 rpm 440 rpm d 40 rpm TAFE SW (Training & Education Support, Industry Skills Unit Meadowbank) 0 age 9 of 49
UEEEEJ07A Air conditioning and refrigeration systems, major components and associated Activity Calculate fan speed and pulley size: In the space below, using the formulas used in the example, determine the new fan pulley diameter when the fan speed of a roof mounted exhaust fan needs to be increased from 60 rpm to 670 rpm. The drive motor rotates at 440 rpm and is fitted with a 90 mm dia. pulley; the fan is fitted with a 0 mm dia. pulley. ew fan pulley exercise calculations Answer: Fans in series Efficient operation can only be obtained when identical fans are used. When two or more fans are connected in series, the volume rate of flow through each unit is the same. The total pressure developed is the addition of each individual fan pressures. Therefore, fans in series deliver the same volume flow rate of air (L/s) but do so at double the static pressure rated for one fan. Single impeller tube-axial fans should not be used in series unless at a distance from each other. The rotational turbulence of the air leaving the impeller of the first fan will change the operation of the second fan and design flow may not be achieved. age 0 of 49 TAFE SW (Training & Education Support, Industry Skills Unit Meadowbank) 0