Commonwealth of Australia 2

Transcription

1 Commonwealth of Australia 2

2 CONSTRUCTION, PLUMBING AND SERVICE INTEGRATED FRAMEWORK TRAINING PACKAGE CPC08 CPCPGS3052A MAINTAIN TYPE A GAS APPLIANCES LEARNING GUIDE ii

3 ACKNOWLEDGEMENTS National Plumbing Services Training Advisory Group Plumbing Industry Commission Victoria Construction and Property Services Industry Skills Council PO Box 151 Belconnen ACT 2616 Tel: This work is copyright, but permission is given to trainers and teachers to make copies and contextualise the resources for use within their own training organisation or in a workplace where training is being conducted. This permission does not extend to making copies for use outside the immediate training environment for which they are made, or the making of copies for hire or resale to third parties. This work was first published in 2004 with the assistance of funding provided by the Commonwealth Government through the Australian National Training Authority (ANTA). The 2015 publication has been updated to reflect changes to the national units of competency. The views expressed in this work do not necessarily represent the views of the Commonwealth of Australia or CPSISC. In addition, the Commonwealth of Australia and CPSISC do not give warranty or accept any legal liability in relation to the content of this work. The website addresses and other contact information provided in this publication were compiled in good faith and were correct at the time of printing. The updating of these resources was completed by: National Plumbing and Services Training Advisory Group, with funding and support provided by the Construction and Property Services Industry Skills Council (CPSISC): This guide was developed in consultation with representatives of the Plumbing Industry by NPSTAG and CPSISC to support the implementation of the CPC08 Construction, Plumbing and Services Training Package. iii

4 Contents What is this resource about?... 1 How do I use this resource?... 1 Flexible Delivery... 1 What do I have to do?... 2 Maintain Type A gas appliances... 3 Unit Descriptor... 3 Element... 3 Performance Criteria... 3 Required knowledge... 4 What other resources will I need?... 6 Safety... 7 Introduction... 8 Properties of gases Electrical safety Type A materials and components Regulations Quality assurance Plan work activities Tools and equipment Determine the maintenance requirements Isolating the gas supply Checking the installation Testing equipment Identifying faults and malfunctions Testing procedure Carrying out the maintenance Thermostats T&PR Valves Rectifying gas supply problems Clean up Worksheet Practical application Assessment checklist iv

5 What is this resource about? Welcome to CPCPGS3052A Maintain Type A gas appliances. This resource will help you gain the skills and knowledge necessary to demonstrate competence in this unit. How do I use this resource? This resource is divided into four main sections: A learning unit, which contains background information on maintaining Type A appliances Worksheets, which prepare you for the practical application Practical application, which allows you to experience maintaining Type A appliances Assessment materials, which help you demonstrate competency. To complete this unit of competence you will need to: read the information contained in the learning unit complete the worksheets as instructed have your answers checked by your trainer or supervisor work with your trainer or supervisor to practise maintaining Type A appliances read the assessment checklist together with the assessment sheets complete the assessment. Learning Resources are not intended to be the only source of information nor are they intended to be an exhaustive form of instruction. Flexible Delivery The Trainer or Supervisor may adapt and deliver this Learning Resource to suit people from diverse backgrounds to meet equity principles and conform to Legislative policies. 1

6 What do I have to do? To demonstrate competence in this unit you will be required to show the level of skills and knowledge for each of the elements involved in maintaining Type A appliances: Plan work activities Determine maintenance requirements Carry out maintenance Clean up. If you are unsure of the meaning of these elements you should read the performance criteria on the following page. 2

7 CPCPGS3052A Unit Descriptor Maintain Type A gas appliances This unit of competency specifies the outcomes required to perform basic maintenance on Type A gas appliances. Element Elements describe the essential outcomes of a unit of competency. Performance Criteria Performance criteria describe the performance needed to demonstrate achievement of the element. Where bold italicised text is used, further information is detailed in the required skills and knowledge section and the range statement. Assessment of performance is to be consistent with the evidence guide. 1 Prepare for work 1.1 Appliance specifications and servicing and manufacturer manuals are obtained for planned work activity 2 Identify maintenance requirements 1.2 Work health and safety (WHS) and environmental requirements associated with maintenance of Type A gas appliances are adhered to throughout the work 1.3 Quality assurance requirements for company operations are identified and adhered to 1.4 Tools and equipment are selected consistent with maintaining Type A gas appliances, checked for serviceability, and any faults are reported to supervisor 1.5 Tasks are planned in conjunction with others involved in or affected by the work 1.6 Work area is prepared and materials identified to support the efficient conduct of maintenance of Type A gas appliances 2.1 Appliance is checked to ensure installation complies with standards and manufacturer requirements 2.2 Electrical safety check is carried out according to authorities' procedures and data is recorded in format required by job specification 2.3 Test equipment is used to support visual inspection and to conduct testing according to statutory and regulatory authorities requirements 2.4 Sustainability principles and concepts are applied throughout the purging process 3

8 3 Conduct maintenance 3.1 Maintenance tasks are carried out according to specifications and manufacturer requirements 3.2 Appliances are checked for operation according to specifications, standards and manufacturer recommendations 3.3 Faults and malfunctions are identified and reported in accordance with workplace requirements 4 Clean up 4.1 Work area is cleared and materials disposed of, reused or recycled according to legislation, regulations, codes of practice, and job specification Required knowledge 4.2 Tools and equipment are cleaned, checked, maintained and stored according to manufacturer recommendations and workplace procedures 4.3 Information is accessed and documentation completed according to workplace requirements Required knowledge for this unit is: documentation and reporting requirements electrical safety and requisite precautions how to access relevant information, including codes and technical standards job safety analysis (JSA) and safe work method statements (SWMS) procedures for maintaining and testing Type A gas appliances properties of gas, gas safety, combustion principles, pressure and flow rates relevant statutory requirements related to maintaining Type A gas appliances SI system of measurements workplace and equipment safety requirements An up to date version of the Unit Descriptor may be located on the Australian Government web site training.gov.au ededdata=true&includesupersededdata=false&homepage=true&javascriptenabled=true&typealltra iningcomponents=true 4

9 How will I be assessed? Your trainer or supervisor will decide with you how you will be assessed. Your assessment activity may include completion of the student worksheet and practical task selected by your trainer or supervisor. Your assessment should allow you to demonstrate all the skills and knowledge required to maintain Type A appliances. This unit may be assessed in conjunction with other units of competence. Your trainer or supervisor will tell you if you are to be assessed this way. Are there any pre-requisites? Prior to commencing CPCPGS3052A Maintain Type A gas appliances you must have completed the following pre-requisites: CPCPCM2043A Carry out WHS requirements It is also recommended that prior to commencing CPCPGS3052A Maintain Type A gas appliances you should have successfully completed the following competencies: CPCPGS3049A Install a Type A appliance flue CPCPGS3053A Disconnect and reconnect services from Type A appliances CPCPGS3058A Install and Commission Type A gas appliances. CPCPGS3051A Purge consumer piping. 5

10 What other resources will I need? To assist you the following resources have been suggested and should be available to you to do this competency: Texts Australian Standard AS/NZS5601 Relevant Version, Gas Installations State and Territory regulations may override this Learning Guide. Web sites Video or audio cassettes 6

11 Safety Workplace health and safety (WHS) requirements need to be observed in accordance with legislation. You need to know the WHS laws governing your job. Revision of CPCPCM2043A - Carry out WHS requirements, before commencing this unit is advisable In any work situation you can reduce the risk of injury to yourself and others by using appropriate personal protective equipment (PPE). The types of PPE that you will need include: overalls used for the protection of the installer when working in different conditions boots it is recommended that soft soled footwear is worn while working on roofs, as deep grooved footwear pick up small stones and debris that might damage or scratch the roof sheets safety glasses or goggles to protect the eyes from injury when cutting the sheets with a power saw ear plugs or muffs to protect the installer s hearing from excessive noise dust masks or respirators to protect the user from breathing in dust or fine particles when cutting the sheets with a power saw gloves, for the protection of the installer s hands when working with different types of pipes, tools and equipment. 7

12 Introduction In this unit you will look at maintaining Type A appliances. Australian Standard (relevant version) AS/NZS5601 defines a Type A appliance as An assembly, other than a vehicle refuelling appliance (VRA), part of which uses gas to produce flames, heat, light, power or special atmosphere. A Type A appliance is an appliance for which an AGA/ALPGA approval scheme exists. Note AGA is the Australian Gas Association. ALPGA is the Australian Liquid Petroleum Gas Association. Type A appliances are generally installed in a domestic situation and include: stoves ovens ranges (including compact ranges for caravans or boats) hot water heaters (storage, instantaneous, pool heaters and continuous flow) gas refrigerators space heaters ducted heating appliances boilers. Note Type A appliances have an energy rating of less than 500 megajoules (mj), if they are certified appliances. An appliance with an energy rating of more than 10mJ is of Type B, if they are not Type A. A Type A appliance, when used in an industrial or commercial application for which it was not intended, is considered to be part of a Type B appliance. 8

13 There are various maintenance tasks that may need to be performed on Type A appliances including: adjusting components such as: thermocouples thermostats T&PR valves pilots burners regulators Before you can maintain Type A appliances there are several issues that you must know, including: properties of gas, gas safety, combustion principles, pressure and flow rates, electrical safety effective isolation procedures characteristics of materials used, types and components of Type A appliances use of testing procedures and equipment in accordance with (relevant version) AS/NZS5601 Gas Installations or AS/NZS1596-LP gas storage and handling. This unit examines typical maintenance procedures for Type A appliances and how to carry out maintenance safely and efficiently. Properties of gas There are four types of gas available to Australian consumers: natural gas (NG) liquefied petroleum gas (LPG or Propane) tempered liquefied petroleum gas (TLP) simulated natural gas (SNG). The following table shows the constituents of the different types of gas. It is important that the gas fitting contractor be aware of the type of gas connected and the properties of that gas. 9

14 Properties of gases NG TLP SNG Propane Hydrogen Oxygen Nitrogen Carbon monoxide Carbon dioxide 2.57 Methane 90.9 Propane Butane Other hydrocarbons Combustion principles When working with gas appliances, you need to know how the gas is ignited and how it burns. These are the principles of combustion. Part of any maintenance procedure on a Type A appliance is to check the level of combustion, identify any causes of incomplete combustion (ie lack of sufficient air to an appliance resulting in incomplete combustion and the generation of potentially fatal gases) and carry out a combustion test if necessary. Combustion is defined as rapid chemical combination of a substance with oxygen, involving the production of heat and light. (The New Oxford Dictionary of English.) Successful combustion requires: fuel (gas in this case) oxygen (from the surrounding air) an ignition source (electronic, pilot or external, ie match). Once ignition has occurred, combustion will continue if a suitable ratio of fuel and oxygen is available. The temperature required for ignition varies, depending on the gas being used. It ranges from 400 C for towns gas to 680 C for natural gas. Most modern appliances reach the required temperature using a high-voltage spark, or a pilot flame, to ignite the gas. 10

15 Pressure Gas is supplied to the consumer under pressure. In Australia, this pressure is expressed in Pascals (Pa). Since this a very low pressure the more usual quantity would be the kilopascal kpa (10000 Pascals) MPa (1000,000 Pascals) The pressure of gas varies from as high as 3mPa in transmission pipes, to 1kPa in some appliances. Many appliances have their pressure rating expressed in different units of measurement. You will need to be able to convert these units to Pascals so pressure can be measured and compared with the compliance plate on the appliance. 1 inch water column = 0.25 kpa 2.04 inch (Hg (mercury) = kpa 1 psi (pound per square inch) = kpa 1 bar = 100 kpa 1 mb (millibar) = 100 Pa 1 atmosphere (sea level) = kpa Pressure has three classifications: low pressure (up to and including 7 kpa) medium pressure (over 7 kpa and up to and including 200 kpa) high pressure (over 200 kpa and up to and including 1050 kpa). Flow rates Flow rates for the gas to the appliance can be controlled using gas pressure regulators. According to (relevant version) AS/NZS5601, gas pressure regulators are required when: any appliance in the premises is not fitted with an appliance gas pressure regulator the intended operating pressure of the consumer piping exceeds the rated working pressure of the appliance gas pressure regulators the gas pressure to a section of consumer piping would otherwise exceed the rated working pressure of the piping, fittings or components in that section. Gas safety Gas is a dangerous fuel if not handled correctly. In an unburnt state it can cause: fire explosion carbon monoxide poisoning asphyxiation. 11

16 Partially burnt gas is also hazardous as it can also cause carbon monoxide poisoning and asphyxiation. The relative density (RD) of the gas will affect its diffusion in air should it escape from the distribution pipes or through a faulty appliance. Gases which are lighter than air rise and mix with the air and are dissipated quickly. Gases such as propane that are heavier than air drop and are slower to dissipate. There is the danger of propane building up in low areas and causing any of the hazards listed above because it is not easily dissipated. Gases also have flammability or explosive limits. These are the minimum and maximum percentage gas to air mixtures that will burn or explode. For example, the lower explosive limit for natural gas is 5% gas to 95% air. The upper explosive limit of natural gas is 14% gas to 86% air. This means if there is less than 5% or more than 14% natural gas in any mix it will not burn or explode. Although gas is generally non-toxic, it can cause asphyxiation by displacing the breathable air in a confined space. Gas is also naturally colourless and odourless and therefore undetectable by sight or smell. For this reason, gas distributors add an odorant so leaking gas can be detected by smell. Inadequate ventilation when using even a correctly maintained gas appliance can still lead to asphyxiation. As the oxygen from the air is used in the combustion process, it is replaced by carbon dioxide, which is a product of combustion. If fresh oxygen is not available via ventilation and the carbon dioxide is not vented outside, breathing can become difficult. Carbon monoxide is also produced in the combustion process. This can replace oxygen in the body and lead to carbon monoxide poisoning. Symptoms of asphyxiation are: faintness weakness partial or complete lack of consciousness a sense of feeling fine lack of ability to carry out simple tasks aggression lips and cheeks turning blue all facial features turning blue-grey. Person may be unconscious at this stage. Symptoms of carbon monoxide poisoning are: dizziness lack of muscle control shortness of breath semi-consciousness a sense of feeling fine and insistence that nothing is wrong, despite above symptoms lips, nose, ears and cheeks becoming a bright cherry colour. 12

17 Note It is a good idea to keep your first aid certification up to date so you know how perform mouth-to-mouth resuscitation and cardio-pulmonary resuscitation. Worksheet Now go to the Worksheet and answer Questions 1 5. Electrical safety Many Type A appliances have an electrical component such as ignition triggers or fans, and all plumbing piping has the capacity to carry electrical current. An electrical bridge needs to be established before cutting any pipes in maintenance or installation work. This is done by cleaning a section of the pipe on both sides of the proposed cut, then attaching a 100 amp spring loaded clamp with insulated handles to both cleaned areas. This is called a bonding strap. The wire between the clamps should be 4 mm 2 insulated copper conductor or equivalent. Creating an electrical bridge 13

18 Earth Wires Earth wires connected to plumbing pipelines MUST NOT be disconnected. These often provide the earth electrode for electrical installations. These wires are considered to be part of the electrical system and can only be altered by a licensed electrical contractor. If part of the maintenance work you are doing requires replacement of the metal water pipes with plastic pipes, an electrical contractor must provide a replacement earthing electrode for the electrical system before the metal pipes are removed. Electrical connections for appliances Plumbers and gasfitters are not allowed to install or interfere with electrical connections unless they are also qualified electricians and hold electrical licenses. You are, however, permitted to plug an appliance requiring an electrical connection into an existing general power outlet (GPO). If the appliance requires hard wiring, that is, a direct connection into the electrical supply, the cord must be left accessible for the electrical contractor. Power point safety tester Gas appliances connected to a GPO may become dangerous if the power point is faulty. A power point safety tester may be used to check if the power point has been wired correctly. A typical power point tester is a sealed three-pin plug with coloured LEDs. These lights indicate the condition of the power point. To use a power point safety tester: turn the power point off plug the tester in look at the lights in both on and off positions compare the lights illuminated to the power point safety tester manufacturer s reference. Three-pin power point safety tester 14

19 Worksheet Now go to the Worksheet and answer Question 6. Type A materials and components Type A appliances are made up of materials and components that must comply with (relevant version) AS/NZS5601 Gas Installations. Components of a Type A appliance cannot be repaired or reused unless they comply with of (relevant version) AS/NZS5601 Materials and components shall be free from damage and defects. Any components that are to be fitted to a Type A appliance must be checked against the standard, as it applies to that type of component, and against the manufacturer s specifications. Regulations When working on any task you must observe the regulations and the WHS requirements in accordance with the State or Territory legislation. Gas installations must be installed and maintained in accordance with (relevant version) AS/NZS5601 gas installations and AS/NZS1596. Installations that do not comply with these regulations can be dangerous to the user. They can be a fire or explosion hazard or an asphyxiation hazard should the gas leak from the pipes or the appliance. It is also important that all installations and maintenance of Type A appliances comply with the manufacturers instructions and recommendations. New appliances will come with instruction manuals for installation and operation. These should be left with the customer for future reference. For older appliances the customer may have kept the manuals. If not, they can be obtained direct from the manufacturer. 15

20 Local gas supply authorities may also have local regulations that need to be followed. Check if this is the case before carrying out any installation or maintenance tasks. Quality assurance Most companies these days have a policy for assuring quality to the customer. This policy is designed to control the processes used within the company such as: record keeping quality of materials used workplace operations and procedures handling procedures use and maintenance of equipment attention to specifications compliance with standards and codes of practice related to maintenance of Type A appliances. You need to be aware of your company s particular quality assurance requirements. A number of quality assurance issues are dealt with in the next section on planning. 16

21 Plan work activities Before you begin the task of maintaining Type A appliances you need to obtain the specifications and appropriate servicing or manufacturers manuals from the job supervisor. Gathering information about the job will help you to make informed decisions about the nature of the job and how to plan and sequence the entire process. Also, before beginning any work, you may need to obtain work notices and submit them to the relevant authorities. The table below shows some information sources and the type of information each source can provide. Source of information The information provided Authorities location and type of service licensing requirements of gasfitters Manuals for servicing parts lists maintenance requirements trouble-shooting guide Job specifications type of appliance service requirements Company s quality assurance procedures to follow company polices on maintenance tasks Regulatory requirements requirements for completion certificates Site inspection type of appliance location of appliance condition of appliance site access Others involved or affected by the work other trade requirements: electrical contractors builders carpenters. Work notices may be required for maintenance tasks. These are required if the work is over a limit set by the local authority (usually $500). Check the limit with your local authority. 17

22 You need to consider how the task you are about to do affects others. You should plan the task with the others involved or affected by the work. Your company may have procedures regarding this that you will need to take into account. It is important to be aware of the effect your work will have on the customer, particularly when working in a residential setting. Often, having a stove, oven, heater or hot water service out of action means serious disruption to the household. It is vital that work is carried out quickly and efficiently with minimum disruption to the customer, and that the site is cleaned up properly at the end of the job. You may need to liaise with other trades when working on Type A appliances. The most common would be working with electrical contractors. When an appliance needs to be isolated from the electrical supply by an electrical contractor, you need to follow the directions of the electrical contractor so you do not begin work before the electrical supply is isolated. Even after the supply has apparently been disconnected, check for residual current using approved testing equipment. Tools and equipment During the maintenance process you will need to have and use PPE to protect yourself, including: overalls boots gloves safety glasses or goggles. All PPE should be fitted and used correctly to minimise the risk of personal injury. You will also need a range of hand and power tools and equipment. This could include: spanners wrenches hand tools power tools measuring equipment testing equipment: manometer multimeter neon tester volt stick 18

23 Lifting equipment: hand trolleys rollers forklifts chain blocks hoists jacks. All tools and equipment must be used correctly and only for the task for which they were designed. If you are unsure how to use a particular tool, ask your supervisor to show you. Lifting equipment will not generally be required in maintenance of Type A appliances. They may be needed only if the appliance cannot be repaired where it is and needs to be transported back to the manufacturer for repair. 19

24 Determine the maintenance requirements Before you can begin to perform any maintenance task on an appliance you need to make sure that it is safe to work on. The supply of gas and electricity needs to be turned off, and the appliance checked to make sure it complies with all Australian Standards. You cannot work on an appliance that does not comply with these standards or any regulation that covers gas or electricity. Remember that any test you perform on an appliance must be done with the correct equipment. Isolating the gas supply To isolate the appliance from the gas supply, the gas must be turned off to the appliance before it is disconnected for maintenance. During the initial installation, isolation valves may have been fitted, allowing quick and safe disconnection of the appliance from the gas supply. If the appliance is installed in a single residential building, isolation valves need not be installed, in which case the gas needs to be turned off at the meter to ensure the appliance is safe. Note Means of isolation for an appliance must comply with (relevant version) AS/NZS Gas Installations. Purging Before beginning any work on consumer piping, the piping may need to be purged. Purging involves removing any gas or air or gas mixture from the pipes to prevent any chance of flash-back or explosion when the appliance is lit. In some circumstances the gas is replaced with an inert gas such as nitrogen or carbon dioxide. In small volume installations, it may be enough to vent the pipe line to the atmosphere. Note Procedures and requirements for purging can be found in (relevant version) AS/NZS5601 and BCS3019A Purging consumer piping. 20

25 Isolating the electrical supply Any electrical connections must also be isolated. For plug-in appliances, this means simply turning off the power point and unplugging the appliance. For appliances wired directly into the electrical supply it may be enough to turn the appliance off. In some cases, disconnection by a licensed electrical contractor may be required. In all cases, testing for residual electrical current and voltages should be done before starting any maintenance work. Checking the installation You will need to check that the appliance has been installed to comply with (relevant version) AS/NZS Gas Installations. Section 5 of the standard covers all aspects of installing appliances that need to be checked, including: requirements for appliances, including second-hand appliances general installation of appliances appliance location air supply to appliances appliance connection appliance gas pressure regulator specific installation requirements. It is important that you are familiar with all the requirements of (relevant version) AS/NZS5601 so you can check the original installation. The procedure for checking this can be found under Commissioning at the end of this unit. If an appliance does not comply with (relevant version) AS/NZS5601, the appliance needs to be disconnected, and the customer and local authority notified. Testing equipment The following equipment can be used to test the appliance gas pressure and electrical safety before carrying out maintenance tasks. 21

26 Manometers Manometers are used to measure the pressure of the gas in the consumer piping and at the appliance. Manometer A U-shaped tube is filled with water to the zero level with both sides open to allow equal atmospheric pressure on both sides. To measure the pressure of the gas, one end of a rubber tube is attached to one side of the manometer with the other end of the tube attached to the gas supply. The pressure of the gas forces the water down in one side of the manometer and up on the other. The height of the water column gives an accurate measure of the gas pressure in Pascals (Pa) or kilopascals (kpa). Measuring gas pressure using a manometer Note Your trainer or supervisor will demonstrate the use of a manometer. 22

27 Multi-meter Multi-meters for plumbing work need to be able to measure to low voltages like the 1mV to 30mV that thermocouples use. Analogue multi-meter Digital multi-meter Multi-meters have an Australian Standard that they should comply with. Any meter used should be fused and the fuse intact. Meters also need to be regularly tested and calibrated. Note Before using the meter, check that the unit is free of damage and that the leads are in good condition. There should not be any exposed wires on the leads that could cause electrocution. Note Remember, a thermocouple should read between 1 mv and 30 Mv. 23

28 Neon tester Neon testers are used to detect any stray electrical voltage and to check that the power has been isolated on appliances connected directly to the electrical supply. Neon tester When you use the neon tester you should follow these directions. Touch the probe end of the neon tester onto the metal part to be tested. Make sure that a good contact is achieved. Place your thumb or forefinger on the operator button. Contact with the button is essential for the neon tester to work. If there is no glow from the neon tester, proceed with the intended work. If the neon tube glows, it means that an electrical voltage is present. Do not proceed with the intended work. The glow from a neon tester is not usually very bright, even under ideal conditions. The brightness of the neon tester will be affected by the following: the amount of voltage present the surrounding light conditions. In bright light you may need to shade the neon tester to improve the possibility of seeing a glow from the tube poor contact made with the probe the earthing conditions (body position) of the operator. Safety note Your trainer or supervisor will demonstrate the use of a neon tester. If the neon tester indicates the presence of an undesirable electrical voltage, immediately take actions to prevent people coming into contact with the hazard. Do not attempt to carry on with your intended work to make repairs to the fault that you have found. 24

29 Identifying faults and malfunctions Appliances need to be checked and any faults or malfunctions identified. Check that: gas is available to the appliance at the correct pressure controls are operating correctly power is available if required for operation the pilot light is lit and operational you have any appliance-specific details as set out by the manufacturer in the trouble-shooting guide supplied with the appliance. Testing consumer piping with appliances connected For consumer piping test procedure refer to section in (relevant version) AS/NZS5601 titled: Testing consumer piping with appliances connected. To test the appliance itself, the procedure for Commissioning an appliance at the end of this unit should be followed. Worksheet Now go to the Worksheet and answer Questions

30 Carrying out the maintenance Now that you have checked the appliance and located any faults, you can begin the maintenance. Maintenance can be routine and performed to the manufacturers specifications or if there may be a need to correct a fault or malfunction. In the latter case the appliance will need to be tested before it is re-commissioned. Thermocouple open Thermocouple closed Failure of the thermocouple If the thermocouple device fails, check the following points. The correct location of the flame, which should be on the junction of the two metals, approximately 3 mm from the end of the thermocouple. Excessive bending of the thermocouple lead can cause a break in the insulation between the inner and outer wire, causing a short circuit. Bad contacts between the thermocouple lead and the electromagnet these contacts must be clean and the joint holding them together should be tightened to hand-tight plus one-eighth of a turn. Insulating washer broken, or missing, causing a short circuit. Electromagnetic coil or contacts broken. Thermocouple test 26

31 Thermostats Thermostats are used to regulate the operation of appliances such as space heaters, hot water heaters, ovens and refrigerators. The thermostat is used to maintain a pre-determined temperature of the air or water. There are four main types of thermostats used in the gas industry. Rod and tube This type of thermostat is made up of a brass tube with an invar steel rod inside that is fixed to one end. The principle of operation is based on the fact that when brass is heated, it expands approximately 18 times faster than invar steel. One end of the brass tube is fixed so expansion can only take place in one direction. When the brass tube expands, the steel rod is pulled in the same direction. The gas valve follows the movement of the invar steel rod. When it is cold, the gas valve will be off its seating, allowing for high gas flow. As the brass is heated, the valve moves closer to its seating and it slowly shuts off the gas supply until there is only enough gas supply to maintain the temperature. A minimum gas supply must be maintained to keep the burner operating safely. This is called the bypass rate. Rod and tube thermostat 27

32 Liquid expansion Liquid expansion thermostats work by attaching bellows to a liquid-filled phial. As the liquid heats, it expands. The expanded liquid is driven up a capillary tube that operates the bellows, which in turn operates the gas valve. Liquid thermostat 28

33 Bimetal There are two types of bimetal thermostat. One has two different metals bonded together and can be straight, U-shaped or coiled. The other is a single piece of steel formed into a spiral inside a metal sleeve. Where two metals are bonded together in a straight piece, an increase in temperature will cause the metal strip to bend up or down, depending on whether the metal strip with the higher expansion rate is on the top or the bottom. When the metals are coiled, the coil will wind in an anti-clockwise or clockwise direction. The bimetal thermostat can be used to control central heating units. The spiral of metal is fixed at one end and attached to a spindle at the other. When the metal is heated and expands, the spiral tightens. This rotates the spindle which then opens or closes electrical switches controlling the gas supply to the unit and electricity supply to the fan. Bimetal spiral 29

34 T & PR Valves Temperature and pressure relief valves (T&PR Valves) are used on hot water service installations. They are used to keep the pressure within the unit at a safe level and to prevent explosions. This valve will relieve any excessive pressure in the hot water service. If this pressure is not relieved, the unit could burst. The T&PR valve is fitted to the hot water service near the top. It will release water from the unit if the pressure inside the unit gets too high or the water temperature too hot. Occasional discharge through T&PR valve during each heating cycle is normal. Continuous discharge indicates a fault. Valves should be manually opened every 3 6 months to prevent corrosion sealing the valve shut. Type caption here 30

35 Discharge from a temperature and pressure relief valve T&PR valves must have a discharge outlet. This outlet must take the discharged water away from the unit and below the unit to prevent back flow or siphoning. Discharge pipes must be open and not have any taps, valves or restrictions installed. The discharge pipe must be less than nine metres and have no more than three bends in it. If it is longer than nine metres, it needs an air break and tundish. If more than three bends are required, the drain length must be shortened by 500 mm for each additional bend. The drain pipe must have a continuous fall and finish between 300 mm and 450 mm above ground with the outlet facing downwards. This will prevent injury from the discharge of hot water. Discharge to drainpipe If the hot water unit is installed internally, the water must be discharged to a point outside the building. External hot water heaters must have their final discharge point at least one metre away from the unit. 31

36 Pilots A pilot flame supplies energy to the main burner and provides the energy to operate the flame-failure device (thermocouple). Owing to the nature of the flame, pilots tend to develop a build up of soot or carbon deposits around the jet. These jets need periodic cleaning or pricking with a fine wire that can get inside the jet to remove this build up. Burners Burners provide the main heat for heat-producing appliances. The burner tubes need to be cleaned of dust and other debris and the primary air port must be clear. The burner body needs to be kept clear of rust and corrosion. Appliance regulators An appliance regulator maintains a constant gas pressure to the appliance. The inlet pressure must be higher than the outlet pressure in order for the appliance to operate correctly. The pressure can be tested using a manometer connected to a test point on the appliance. If found to be faulty, an appliance regulator needs to be replaced. 32

37 Rectifying gas supply problems Meters and service regulators If the fault is found to be at the meter or service regulator, the problem must be referred to the gas supply company. Unauthorised personnel are not permitted to work on these sections of the gas supply. Replacement of non-direct wired fans Non-direct wired fans are found in: central heaters space heaters appliance power flues. In the event of a faulty fan, the procedure set out by the manufacturer for the specific appliance must be followed. The service manual for the appliance will contain this procedure. Worksheet Now go to the Worksheet and answer Questions Commissioning the appliance When all the repairs have been completed, the appliance needs to be tested to make sure it is reinstalled according to (relevant version) AS/NZS5601. Prior to commissioning For internally installed appliances, it is good practice to set out a drop sheet to protect the floor covering. Do not sit tools on finished surface of appliance. Check the following: you have read the manufacturer s instructions you understand the operation of the appliance if an appliance requires electricity, it is plugged in and turned on the gas line is complete and the gas is turned on you have all the necessary tools ready and at hand such as: electrical safety test equipment safety glasses protective clothing and footwear manometer and hose appropriate screwdrivers and spanners adjustable wrenches soapy water solution. 33

38 Commissioning steps Safety glasses must be worn. Test for stray electrical current with neon tester. Check the power point with power point safety tester. Purge the pipe-line (use bonding straps). Re-test the joints for leaks. Read the compliance plate to establish the correct burner pressure. Locate the test point and connect the manometer. Once connected, do not leave unattended and protect rubber hose from flame. If an appliance has a pilot and burner: ignite the pilot check the pilot flame and adjust if necessary (or if possible) turn on the main burner check the pressure and adjust it if necessary (minimum gas rate if applicable) check the appearance of the main flame and adjust the burner aeration if necessary turn off the appliance and disconnect the manometer reassemble the panels, knobs, etc advise the customer on the operation of the appliance. Information you may need to know about the appliance Type of safety cut-out device. Type of thermostat. How and when the safety cut-out device and thermostat operates. Where the readings are taken from on the manometer. Where information regarding the appliance is found. Any other information regarding the appliance you are installing, eg auto ignition, valves, solenoid valves, test points and operation instructions. 34

39 Clean up When you have completed the maintenance you must clean up the work area. Tools and equipment should be cleaned and stored for future use. This is especially important with measuring and testing equipment. You should ensure that: the work site is cleared of debris and waste safely disposed of tools and equipment are cleaned, maintained and stored all manuals for the appliance have been left with the customer the customer knows how to operate the appliance correctly. Worksheet Now go to the Worksheet and answer Questions

40 Name: Worksheet CPCPGS3052A Maintain Type A gas appliances The student should complete this worksheet before attempting the practical installation. The worksheet may form part of the assessment and should be checked and signed off by your trainer or supervisor. 1. What do the following abbreviations mean? mj kpa Pa mv 2. Combustion is a technical term for burning. Can this process be carried out in the presence of air? 3 (a) State the lower flammability limit of a mixture of natural gas and air. % gas % air (b) Tick the correct answer. A room is filled with 20% natural gas and 80% air. Will it ignite? It might It will not It will 36

41 4. List the major requirements of complete combustion. 5. List six (6) symptoms of carbon monoxide poisoning. 6. Describe the method of creating an electrical bridge using bonding straps. 7. Name four items of test equipment you will need as a gasfitter. 37

42 8. What do you need to do if you find the installation of an appliance does not comply with the requirements of (relevant version) AS/NZS5601? 9. Which of the following components may be repaired if faulty? (circle the correct answer). a. Thermocouples b. Thermostats c T&PR valves d. All of the above e. Non of the above f. All of the above as long as they comply with Clause of (relevant version) AS/NZS (a) How do you test for effective isolation of an appliance from the gas supply? (b) How do you test for effective isolation of an appliance from the electricity supply? 38

43 11. What is the purpose of the flame failure device such as a thermocouple? 12. When the thermocouple is in operation, what holds the inlet valve open? 13. What is the purpose of a thermostat? 14. (a) What two materials make up the temperature sensor on a rod and tube thermostat? (b) Which of these materials expands the most and why? 39

44 15. What are the requirements for the discharge from a T&PR valve? 16. Where should the discharge from a T&PR valve terminate? 17. Why is it necessary for a T&PR valve to be manually released every 3-6 months? 18. How do you keep pilot jets free from dust and carbon deposits? 19. A constant pressure regulator is installed before the meter. Are you allowed to alter or adjust this regulator? Yes No 20. Why are constant pressure regulators installed on appliances? 21. Where will you find the procedure for replacement of non-direct wired fans for a Type A appliance? 40

45 22. At what stage during commissioning should you wear safety glasses? 23. What test equipment do you need to complete the commissioning process? 24. What type of data is provided on an appliance data plate? Trainer or Supervisor s Signature:.. Date of Completion:. 41

46 Name: Practical application CPCPGS3052A Maintain Type A gas appliances Your trainer or supervisor will now work with you to demonstrate and explain Maintain Type A appliances. The following points will be covered. Appliance specifications and servicing or manufacturers manuals obtained for planned work activity WHS requirements associated with the conduct of maintenance of Type A gas appliances, and the workplace environment, are adhered to throughout the work Quality assurance requirements for company operations are identified and adhered to Tools and equipment are selected consistent with maintaining Type A appliances, checked for serviceability and any faults reported to supervisor Tasks are planned in conjunction with others involved in or affected by the work Work area is prepared to support the efficient conduct of maintenance of the Type A gas appliance Appliance is checked to ensure installation complies with standards and manufacturer s requirements Electrical safety check is carried out in accordance with authorities procedure and data is recorded in the format required by the job specification Test equipment is used to support visual inspection and to conduct testing in accordance with authorities requirements Maintenance tasks are carried out in accordance with specifications and or manufacturer s requirements Appliances are checked for operation in accordance with specifications, standards and manufacturers recommendations Faults and malfunctions are identified and reported in accordance with workplace requirements 42

47 Work area is cleared and materials disposed of or recycled in accordance with State or Territory legislation and workplace procedures Tools and equipment are cleaned, checked, maintained and stored in accordance with manufacturers recommendations and workplace procedures Documentation is completed in accordance with workplace requirements On completion of this practical application you will be assessed. To prepare for your assessment make sure you read the Assessment checklist, the Assessment task and Questions. Trainer or Supervisor s Signature:.. Date of Completion: 43

48 Assessment checklist CPCPGS3052A Maintain Type A gas appliances Worksheet Criteria Yes No Have the worksheets been successfully completed? Has the practical task been completed? Are the job specification and local authorities or utilities requirements available? Trainer or Supervisor s Signature:.. Date of Completion: 44