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Diagnose and rectify faults in air conditioning and refrigeration systems and components



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  1. List the steps in conducting a risk assessment prior to a task being conducted.


The steps are given below:

  1. Risk will be identified
  2. Decide eventually who may be harmed or hurt and how
  3. Assess the risks and then decide on the particular provisions
  4. Record all the findings and then implement all of them
  5. Review the assessments and then update them if required (Kabeel, et al., 2016).


  1. You are going to purchase refrigerant, compile a risk assessment for that activity.


Potential hazard

  1. Flammability
  2. Toxicity


Risk rating

  1. 3
  2. 4


Risk control measures

  1. Always utilize sufficient ventilation
  2. Temperature should be changed frequently


Risk after control measures

  1. Store combustible and flammable liquids away from all discordant materials
  2. Safety gloves and goggles should be used


  1. List the risk associated when working on a compressor that is driven by a external electric motor and name a control measure that can be put in place


The risks are given below:

  1. a) High level of noise
  2. b) High pressures
  3. c) Electrical hazards
  4. d) Fumes

The control measure is that safety gloves and goggles should be used (Kabeel, et al., 2016).



  1. As an employee what is your workplace health and safety obligation when working on a refrigeration system


Health and safety obligations are given below:

  1. Wear protective coveralls or suits for preventing potential adulteration of clothing
  2. Wear nitrile internal gloves for preventing exposure to all liquids and also when excluding cleaning and PPE tools


  1. What rights does a officer from the Electrical Safety Office have


The rights are given below:

  1. Certifying, registering and accrediting electrical licenses
  2. Managing electrical licenses of contractors and workers
  3. Ensuring that standards and laws of electrical safety are followed (Gresh, 2018).


  1. Injuries that can occur when working with or close to rotating or moving machinery include

(please circle)


  1. Entanglement of clothing in moving parts
  2. Entrapment from running nips
  3. Crush and shear from moving parts
  4. All answers listed


  1. As a electrical licence holder you are required to get regular CPR training
    • TRUE / FALSE
  1. When working on electrical components of a refrigeration system the best way to ensure your safety is to
  1. make sure you have competent offsider
  2. make sure that the circuit you are working on is properly isolated and tagged
  3. make sure that you get a good nights sleep
  4. avoid using a megger


  1. What four (4) factors determine the results of an electric current passing through a human body


  1. Magnitude of the current
  2. Duration of current flow
  3. The isolation factor
  4. Type of current AC. or DC
  5. The weather conditions
  6. Portion of the heart’s cycle


  1. List the treatment for electric shock


It includes the following:

  1. Switch off the electricity source
  2. Start CPR if the individual does not show any circulation like coughing, breathing
  3. Protect the injured individual from getting chilled
  4. Apply the bandage (Gresh, 2018).



  1. What is the purpose of a Risk Assessment?


Risk assessments help in identifying intrinsic risks of the business and also give controls, processes and measures for decreasing the implications of risks to operations of the business.


  1. The basic principles of Risk Management include


The basic principles are given below:

  1. Identification of risks
  2. Analysis of risks
  3. Control risks
  4. Financing of risk
  5. Management will claim (Thornton & Wagner, 2012).


  1. A Risk assessment / safety checklist for a workshop must comply with what legislation


Management of Safety and Health at Work Regulations


  1. List the effects of an electric shock


The effects are:

  1. Tingling
  2. Pain
  3. Weakness
  4. Numbness


  1. List the precaution to be observed when handling refrigerant and explain why:


The precautions to be observed are given below:

  1. a) Contact of skin with liquid refrigerant should be avoided as it could cause frostbite
  2. b) Breathing of refrigerant vapour should be avoided. Be very aware that breathing major concentrations of vapour of refrigerant is very harmful and it might cause heart irregularities or also death (Thornton & Wagner, 2012).


  1. When working on a unit in a location where there is a risk of exposure to refrigerant gases what precautions should be taken


The precautions are:

  1. Utilize safety gloves and goggles
  2. Spilling of liquid refrigerant on the skin should be avoided (Rausand, 2013).


  1. A refrigerant management program should include


It should include the following:

  1. Accessibility of recycling and recovery equipment in adequate quantity for performing work within regulations of EPA
  2. Responsibilities for mainly maintenance and care of recycling and recovery equipment mainly including recordkeeping.


  1. Under the Ozone Protection Regulations who must keep records of controlled substances?


  1. The refrigerant wholesaler and equipment owners
  2. The refrigerant wholesaler and the servicing company
  3. The servicing company and the equipment owners
  4. The local council and the equipment owners.


  1. Prior to conducting any work requiring the handling or use of refrigerant the worker is required to have what?


The worker is needed to wear accurate and approve eye prevention and gloves and also should not wear loose-fit clothes (Rausand, 2013). 



  1. Briefly describe three precautions to be observed when handling refrigeration oil


  1. Always utilize sufficient ventilation
  2. Do not trap refrigerants mainly between valves where particularly no device of pressure relief
  3. Do not disclose refrigerants to sparks or flames


  1. List the storage requirements of refrigerant cylinders


  1. They must be stored in accurate ventilated temperatures and area
  2. Make sure that entire cylinders of refrigerant have devices that release pressure for avoiding explosions or combustion



  1. Prior to working on a the electrical parts of a refrigeration system what steps must be taken


  1. Compressor will be used
  2. Condenser will be used for removing heat mainly from vapour gas of refrigerant
  3. Then expansion device is used for creating a fall in pressure
  4. Then the last evaporator is used for absorbing heat


  1. What restrictions are placed on whom may be granted an authorisation to engage in ‘restricted activities?


The restrictions are given below:

  1. Should not utilize equipment with frayed cords
  2. Do not permit anyone to enter the restricted area


  1. What must be fitted to a nitrogen cylinder to ensure the safety of the user when pressure testing a system


A drain valve should be fitted in the nitrogen cylinder.


  1. What is the function of a compressor?


(A) To pump refrigerant and oil around a refrigeration system

(B) To create a pressure drop in a refrigeration system

(C) To be the heart of the refrigeration system

(D) To draw superheated vapour away from the evaporator.


  1. What is the purpose of the shaft seal?


(A) To prevent oil loss and non-condensable entry

(B) To prevent air and non-condensable entry

(C) To prevent refrigerant and oil loss

(D) To prevent refrigerant loss and air entry.


  1. What is used to maintain the gas seal on helical gears of a screw compressor?


(A) A mechanical seal

(B) Oil being pumped into the compressor

(C) Refrigerant, oil and a mechanical seal

(D) The refrigerant gas itself once it gets to a high enough pressure


  1. The function of a condenser is to:


(A) change a superheated vapour to a saturated liquid

(B) change superheated vapour to a subcooled liquid

(C) change saturated vapour to a saturated liquid

(D) change subcooled vapour to a superheated vapour


  1. Where does the heat go to from the condenser?


(A) Into the refrigerated space

(B) Into the evaporator

(C) Into the cooling medium

(D) Into the product



  1. Name the five main compressor types and briefly describe their operation (how it works)


Five main compressors are:

  1. Rotary screw compressor – In this, two copulated rotors meshes jointly then trap the air and decrease the air volume with the rotors.
  2. Reciprocating Compressors – These have a piston that is mainly driven by the electric motor and crankshaft.
  3. Vane Compressors – The vanes are mainly pulled out by centrifugal pressure when the compressor is mainly rotating and also the vanes then move out and in of the slot as the rotors are peculiar to the particular casing.
  4. Compressor Motors – These are utilized for providing the power for driving compressors.
  5. Piston compressor – It moves firstly downward and then draws some air into the cylinder


  1. Give a typical application for each of the main compressor types
  2. Reciprocating Compressors – These are very ordinary compressors that are found mainly in applications of mobile.
  3. Rotary Screw Compressors – These were mainly found in applications of stationary
  4. Rotary Vane Compressor – These are the least ordinary compressor that is found in the application of mobile


  1. What are the three general styles of compressors,
  • The three general classifications given to compressors are:
  1. Rotary Vane Compressors
  2. Rotary Screw Compressors
  3. Piston Compressors


  1. List and describe the two ways to lubricate a compressor


The two ways to lubricate a compressor are:

  1. Splash systems of lubrication – In this oil is mainly applied to the pistons and cylinders by particularly rotating all dippers on the related-rod bearing caps
  2. Pressure systems of lubrication – It is the system where the pump of oil accurately spreads the oil to the main surfaces of the pump.


  1. Briefly describe the action of the valve plate on a reciprocating compressor


Valve plates are utilized in the extensive range of mainly compressor claims across various compositions of gas mainly acting as covers between distinct zones of pressures within the air compressor.



  1. List the three main types of condenser


  1. Water-cooled condenser
  2. Air-cooled condenser
  3. Evaporative condenser (Schermerhorn Jr, et al., 2020).


  1. What is the difference between primary surface area and secondary surface area


The primary surface area gives refrigeration mainly by undergoing the process of phase alteration in the evaporator. The secondary surface areas don’t experience the change of phase as they mainly transfer energy from one place to another.


  1. What is the purpose of a cooling tower


Its purpose is to exclude heat from the facility or building by spewing water down mainly through the tower for exchanging heat into the interior part of the building.


  1. Do all systems need a liquid receiver? Explain your answer


Yes, entire systems required the liquid receiver as it makes sure that liquid refrigerant is particularly entering the device of expansion.


  1. Describe the operation of water regulating valve


It regulates the flow of water for maintaining the high-side pressure of the system and also stops the water flow when the particular system turns off to mainly reduce the waste of water (Schermerhorn Jr, et al., 2020). 


  1. What is the function of a refrigerant flow control?


(A) To meter refrigerant into the evaporator

(B) To meter refrigerant into the condenser

(C) To meter oil out of the evaporator

(D) To control motor current draw.


  1. What are the three forces acting on the diaphragm of a TX Valve?


(A) Spring pressure, bulb pressure, evaporator pressure

(B) Atmospheric pressure, bulb pressure, evaporator pressure

(C) Spring pressure, atmospheric pressure, evaporator pressure

(D) Spring pressure, bulb pressure, atmospheric pressure.



  1. Why do you need to regulate the flow of refrigerant into an evaporator coil



There is a need to regulate the flow of refrigerant into an evaporator coil to prevent the liquid return to the refrigerant to the compressor. The high-pressure and low-pressure sides are separated by TXV of a conditioning system or refrigeration (Abed, & Fathi, 2018).


  1. What is the purpose of a filter/drier in a refrigeration system



The purpose of a filter/ drier is to absorb the contaminates of the system like water, which may form acids, and two, o provides the physical filtration.


  1. What are the two functions of the heater wired across the thermostat in a cyclic defrost refrigerator?


(A) To ensure the evaporator is completely defrosted and to prevent very long off cycles

(B) To stop the evaporator becoming too cold and to prevent the product from freezing

(C) To create a load on the off cycle and to stop the compressor from short cycling


  1. Domestic cyclic defrost refrigeration systems use the hot gas from the compressor to defrost the evaporator




  1. Before testing a live known circuit with an electrical testing instrument, you should:


(A) check the battery in the instrument

(B) ensure you are properly earthed before testing

(C) test against a live known circuit before testing the circuit

(D) test against a live known circuit, test the circuit and finally retest against a live known circuit


  1. Care should be taken when removing refrigerant from a domestic refrigerator:


(A) to avoid losing refrigerant to atmosphere

(B) to avoid getting oil on the customers floor

(C) to ensure minimal refrigerant is left for pressure testing

(D) to ensure all the oil and refrigerant is removed before pressure testing


  1. When working in a customer’s house, who is responsible for your safety



When the person is working in the customer’s house the person who will be responsible for the safety is the business owner or the property manager who is expected to expected the provide the person a safe working space (Abed, & Fathi, 2018).


  1. List the six basic types of domestic refrigerators and briefly describe each type


Some basic types of domestic refrigerators are-

1) French door- in its top, there are two doors and at its bottom, there is a drawer.


2) Side by side- in this type, there are two doors. These doors open from the centre and on the side of the refrigerator there is a freezer on the other side.


3) Top freezer- it provides easy access to the frozen item and in it freezer is located below the refrigerator. It has also different doors for each.

4) Bottom freezer- in this the type at bottom the freezer is and on the top there is refrigerator. Each door opens from the sides. It provides easy access to the fresh items.


5) Under counter- it is installed under the counter and its doors open from the sides. It has single reversible door and it also has also the ability to form specialized temperature zones.


6) Quad Door- it has four doors which open from the centre. Its freezer has two doors which is on the bottom and on top the freezer has two doors on its top (Guo, et al., 2018).


  1. List the three types of condensers used on domestic refrigerators



Three types of condensers that are used on domestic refrigerators are-

1) Double tube condensers

2) Shell and coil condensers

3) Shell and tube condensers




  1. What is the most common type of charging adaptor? Does this type of adaptor agree with the Domestic Code of Good Practice?



Some common types of charging adaptors are-

1) Micro USB cables

2) Type A charger cable

3) Type B charger cable

4) USB type C cable

5) Apple’s lightning charger

No, this type of adopter does not agree with the domestic code of good practice.


  1. How is the evaporator different in an upright freezer, compared to a chest freezer?


An upright freezer is having a number of various small roll-bond evaporator coils which will just double the shelving. An upright freezer is also known as stand-up freezers because they are vertical (Ahmad, et al., 2018).


  1. What would be the average saturated suction temperature for a domestic deep freezer?


(A) 0° C

(B) -50° C

(C) -30° C

(D) -20° C


  1. What is the preferred measuring device for measuring a vacuum in a domestic system?


(A) Mercury manometer

(B) Bourdon tube gauge

(C) Anemometer

(D) Electronic vacuum gauge


  1. Before looking for a replacement component from a manufacturers catalogue, you should:


(A) Ensure the component is definitely in need of replacement

(B) Ensure the customer is aware that you are looking to replace a component.

(C) There are no other faults present

(D) All of the above


  1. What would happen if the three way defrost solenoid valve was leaking so the refrigerant could flow into the condenser and up the defrost line?



If the three-way defrost solenoid valve was leaking, then there is chances that the spikes or electrical surges can damage the coil. In this case the high compressor also discharges the temperatures.


  1. There are a number of steps involved in selecting a replacement thermostat from a manufacturer’s catalogue. List and describe each step below.



Some of the steps which can be followed to select the replacement thermostat from the catalogue of manufacturers –

1) First of all it is determined which thermostat is most compatible with the air system type and heating system type.

2) Then the second is to learn about the choose thermostat type.

3) After learning, the programming options are choosing.

4) And at the lest, thermostat is installed.



  1. You find a domestic compressor to be faulty and are required to replace it. What details are required from the name plate of the existing compressor to assist select the replacement compressor?



From the nameplate of the existing compressor, the details which are required are-

1) Compressor model number

2) Manufacturer

3) Serial number


  1. Noisy operation of a compressor could be a sign that



Noisy operations of a compressor can be a sign of the lose refrigerant tubing or it can also be sign of the broken spring or loose bolts. In other words, it indicates the loss mount or loses internal part.



  1. Excess ice formation on the coils of the evaporator would indicate



It indicates that the refrigerant is going through the evaporators can’t extract enough heat when the air conditioner system, airflow goes below a certain level. It also means that the coils can get rid of cool air.


  1. List 5 reasons that could cause a compressor to overheat



Some of the reasons are-

1) When the condensing coils are not clean.

2) When the discharge line is ILL-fitted.

3) When the condenser air is block.

4) When the fan of condenser is inconsistent.

5) When the refrigerant is overcharging.


  1. Freezing up of TX valves can be caused by



It can be caused due to the too hot superheat. When the refrigerant is to low or when in the refrigerant is having excessive moisture.


  1. List the procedure for replacing a compressor on a domestic



The procedure which will be followed for replacing the compressor is-

1) The refrigerant is tested.

2) System is flushed

3) In other compressor oil is checked.

4) Refrigerant is pumped out.

5) The compressor is replaced.

6) System check is performed

7) Maintenance must be carried out on regular basis.



  1. Detail the procedure to remove test and replace a thermostat on refrigerator



Procedure which must be followed-

1) The refrigerator will be prepared to replacement.

2) The thermostat will be located

3) Shelving will be removed

4) Wires will be removed

5) Broken thermostats will be taken out.

6) New thermostat will be installed.

7) Refrigerator will be tested (Zaitsev, et al., 2020).


  1. How is Sludge formed in refrigeration system and what can it result in



With an increase in temperature, sludge is more likely to form, and its composition is made up of worn metal and drying agent in case of reciprocating compressors, & tarry matter produced by decomposition of refrigerator oil and polymerization in the case of centrifugal compressors. Whether or not a drying agent is used in centrifugal compressors is associated with sludge formation, as the contaminated conditions on the inner capillary wall greatly influence sludge formation.

It can result in the chemical breakdown of oil (Cao, et al., 2020).


  1. What is the purpose of a reversing valve and where is it most commonly used



The purpose is to control the direction of refrigerant flow and it is most commonly used in reversing refrigerant flow.




  1. List the protective devices that can minimise the chance of an electrocution occurring from indirect contact
  • Answer
  • Fuses protect equipment and can reduce the chance of occurring electrocution (Malinina, et al., 2020).


  1. List suggested weekly maintenance tasks that should be conducted on an air conditioning unit



1) It filter must be cleaned and replaced routinely.

2) The condensate drain line must be checked and clean.


  1. RCD’s are devices that




RCDs are devices that can be within t10 to 50 seconds if there is any kind of electrical fault.


  1. Fill in the blank spaces


One of the most important service and diagnostic tools is the HVACR.   They are used to check the maintenance and__repairs _in the refrigeration system when not in use must be kept in _the garage, basement, utility closet, and attic_.

  1. Why must R22 or any other refrigerant service equipment never be used on R410A equipment



R22 must not be used on R410A equipment because due to the different chemical reactions of the two refrigerants, the compressor will have to move both fluids through the same coils.


  1. What is the purpose of a refrigeration lubricant?




The purpose of refrigeration lubricant is to minimize the friction and works as the protection or seal between the low pressure side and high pressure side (Zhou, et al., 2020).



  1. When must a leak test be carried out on a refrigeration system



When there is 3 to 30 kg HRCs in system and it is leak then it must be annually tested.


  1. How should refrigerant cylinders stored




They must be stored in dry, cool, well- ventilated, area which is fire- resistance and which fulfils the regulations of state, federal and local.


  1. What is the purpose of a cooling tower for a water cooled system



Its purpose is to discard the heat from the facility or building by sprinkling the water through the tower So that heat can be exchanged from the sides of the building (Sun, et al., 2019).


  1. Using the attached Charts work out the temperature and pressures for a particular system

A butchers cool room at 6 0C is not cold enough and the suction pressure gauge reads 10 kPa  (-100C) the evaporator is forced draft and the refrigerant is R134A. What should the suction pressure when the unit is operating at the correct temperature for its application?



Suction pressure must be of R 134a which is 0 to 5 lbs psig.


  1. Using the attached Charts work out the temperature and pressures for a particular system

A freezer cabinet with an plate evaporator is operating at -170C what suction temperature would you expect the refrigerant in use is R507




The suction temperature which would be expected is off 0 to 5 lbs psig (Yuan, et al., 2019).


  1. Using the attached Charts solve the following

You have been called to identify refrigerant in an unmarked cylinder the compound gauge reads a pressure of 469 kPa and the temperature of the cylinder is 200C what is the refrigerant type



The type of refrigerant is ChloroFluoroCarbons



  1. Complete the following Diagnostic table for faults a domestic freezer


Trouble Probable Cause Remedy or Repair
Unit runs to much (all the time the time)  

When the evaporator coil is dirty


Clean the evaporator coil
When the evaporator coil is frozen




Defrost the evaporator coil
When the air filter is clogged



Clean the air filters
Restrictive filters



Use filters with a lower MERV value


Repair the leak and to correct level restore the refrigerant


Faulty thermostat

Replace the thermostats

Blocked or Dirty condenser


Clean the condenser




  1. Using the attached Pressure Temperature Tables complete the following table


Refrigerant type Pressure ( KPa) Temperature (0C)
HFC R134A 257 122 degree
HFC R410A liquid 70 MPa -20
HCFC R22 358 62.8
HCFC R401B vapour 144 -20
CFC R12 22 to 57 MPa -25





End of Assessment




Abed, E. M., & Fathi, A. A. (2018). Experimental and numerical investigation of metastable flow of refrigerant R-22 through capillary tube. The Iraqi Journal for Mechanical and Materials Engineering18(1), 41-62.

Gresh, T. (2018). Compressor performance: aerodynamics for the user. Butterworth-Heinemann.

Guo, Y., Tan, Z., Chen, H., Li, G., Wang, J., Huang, R., … & Ahmad, T. (2018). Deep learning-based fault diagnosis of variable refrigerant flow air-conditioning system for building energy saving. Applied Energy225, 732-745.

Guo, Y., Wang, J., Chen, H., Li, G., Huang, R., Yuan, Y., … & Sun, S. (2019). An expert rule-based fault diagnosis strategy for variable refrigerant flow air conditioning systems. Applied Thermal Engineering149, 1223-1235.

Kabeel, A. E., Omara, Z. M., Essa, F. A., & Abdullah, A. S. (2016). Solar still with condenser–A detailed review. Renewable and Sustainable Energy Reviews59(C), 839-857.

Rausand, M. (2013). Risk assessment: theory, methods, and applications (Vol. 115). John Wiley & Sons.

Schermerhorn Jr, J. R., Bachrach, D. G., & Wright, B. (2020). Management. John Wiley & Sons.

Thornton, B., & Wagner, A. (2012). Variable refrigerant flow systems. Pacific Northwest National Laboratory1.

Zaitsev, A. V., Malyshev, A. A., Kouadio, K. F., Malinina, O. S., & Lisovtsov, A. O. (2020, November). Heat-hydrodynamic analysis of two-phase flow at refrigerant in-channel boiling. In AIP Conference Proceedings (Vol. 2285, No. 1, p. 030020). AIP Publishing LLC.

Zhou, Z., Li, G., Wang, J., Chen, H., Zhong, H., & Cao, Z. (2020). A comparison study of basic data-driven fault diagnosis methods for variable refrigerant flow system. Energy and Buildings224, 110232.






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