Manual for Refrigeration Servicing Technicians - UNEP - Division of ...

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4 Servicing Practices Servicing RAC systems The main concept and procedures of each operation is the same for all refrigeration and air-conditioning systems. They differ only in each system specific connectivity requirements or tools to be used. Most of servicing activities to RAC systems –dealing with refrigerants – falls within the one of the following main operations: Evacuation 4 Purging (cleaning) 4 Leak detection 4 Charging 4 Recovery 4 90
4 Servicing Practices Evacuation A refrigerating system must contain only the refrigerant in liquid or vapour state along with dry oil. All other vapours, gases, and fluids must be removed. Connecting the system to a vacuum pump and allowing the pump to run continuously for some time while a deep vacuum is drawn on the system can best remove these substances. It is sometimes necessary to warm the parts to around +50°C while under a high vacuum; in order to accelerate the removal of all unwanted moisture, heat the parts using warm air, heat lamps, or water. Never use a brazing torch. If any part of the system is below 0°C, the moisture may freeze and it will take a considerably longer time for the ice to sublimate to vapour during the evacuation process. The equipment necessary to carry out the evacuation is: PAGE 06 PROCEDURES TO PERFORMS • vacuum pump • manifold gauges two servicing valves (in the case system is not equipped with servicing valves) • vacuum gauge. It is essential to know that conventional manifold gauges have low sensitivity, particularly at lower pressures. As such, they are ineffective at determining whether or not a sufficient vacuum has been achieved. Therefore it is essential to ensure that a proper vacuum gauge (such as a Pirani gauge) is used. To understand why system evacuation is very important for moisture elimination, it is useful to remember the concept of vacuum and the relationship between boiling temperature and pressure. For a pure substance, like water, the boiling temperature for a fixed pressure is called saturation temperature at this pressure, and the pressure at which the water evaporates at a fixed temperature is called saturation pressure at this temperature. The relationship between these two thermodynamic properties (a natural law) is presented in the figure for water: PRESSURE [kPa] 160 140 120 100 80 60 40 20 0 -75 -35 5 45 85 125 TEMPERATURE [ ° C] Saturation pressure and temperature curve for water It can be seen in this figure that as the pressure reduces, the boiling temperature will be lower. If one wants to remove moisture in DONE vapour phase from a refrigeration system, it is very important to lower the system pressure because this will facilitate the change of the moisture from liquid to vapour phase (through heat transfer from the surrounding environment) making its removal easier. Always evacuate a system when: • replacing a circuit component (compressor, condenser, filterdrier, evaporator, etc.) • whilst the system has no refrigerant • if the refrigerant is contaminated • after the lubricant is charged. 91
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Manual for Refrigeration Servicing
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Introduction When to use the manual
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Introduction The Factors affecting
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Introduction How to assess conditio
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Introduction Characteristics of Sel
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Introduction Another form of refere
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Introduction Choose your chapter Th
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1 Environmental impact of refrigera
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1 Environmental Impact The ozone la
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1 Environmental Impact RADIATION FR
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1 Environmental Impact The ozone la
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1 Environmental Impact Effects of o
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1 Environmental Impact The greenhou
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1 Environmental Impact Timeline act
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1 Environmental Impact Alternative
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1 Environmental Impact The way forw
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2 Refrigerants 2.1. Section objecti
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2 Refrigerants Chemical properties
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2 Refrigerants Safety characteristi
Page 39 and 40: 2 Refrigerants Types of refrigerant
Page 41 and 42: 2 Refrigerants Those with ozone dep
Page 43 and 44: 2 Refrigerants Those with zero ozon
Page 45 and 46: 2 Refrigerants Carbon dioxide (CO2,
Page 47 and 48: 2 Refrigerants Azeotropic Blends An
Page 49 and 50: 2 Refrigerants Using Refrigerant Bl
Page 51 and 52: 2 Refrigerants Lubricants Today, al
Page 53 and 54: 2 Refrigerants Refrigerants and app
Page 55 and 56: 2 Refrigerants Properties of most c
Page 57 and 58: 3 Refrigerants Content Management M
Page 59 and 60: 3 Refrigerant Management The majori
Page 61 and 62: 3 Refrigerant Management Handling o
Page 63 and 64: 3 Refrigerant Management Recovery c
Page 65 and 66: 3 Refrigerant Management Refrigeran
Page 67 and 68: 3 Refrigerant Management Refrigeran
Page 69 and 70: 3 Refrigerant Management Open Refri
Page 71 and 72: 3 Refrigerant Management CHAPITRE 3
Page 73 and 74: 3 Refrigerant Management Recycling
Page 75 and 76: 3 Refrigerant Management equipment
Page 79 and 80: 3 Refrigerant Management PAGE 22 Ex
Page 83 and 84: 3 Refrigerant Management Further re
Page 85 and 86: Summary This section will provide t
Page 87 and 88: 4 Servicing Practices Moisture Mois
Page 89: 4 Servicing Practices Non-condensab
Page 93 and 94: 4 Servicing Practices 7 - For large
Page 95 and 96: 4 Servicing Practices Pressure unit
Page 97 and 98: CHAPITRE 4 4PAGE 10 LEAK DETECTION
Page 99 and 100: 4 Servicing Practices Detection met
Page 101 and 102: 4 Servicing Practices CHAPITRE 4 PA
Page 103 and 104: 4 Servicing Practices Volumetric ch
Page 105 and 106: 4 Servicing Practices Electronic ch
Page 107 and 108: 4 Servicing Practices Why charge re
Page 109 and 110: 5 Retrofitting Content General retr
Page 111 and 112: 5 Retrofitting • Upon evaluation
Page 113 and 114: 5 Retrofitting General retrofitting
Page 115 and 116: 5 Retrofitting procedures that you
Page 117 and 118: 5 Retrofitting MVAC retrofitting pr
Page 119 and 120: 5 Retrofitting Although, in general
Page 121 and 122: 5 Retrofitting Further reading UNEP
Page 123 and 124: 6 Summary 6.1. Overview of refriger
Page 125 and 126: 6 Safe Refrigerant Handling Oxygen
Page 127 and 128: 6 Safe Refrigerant Handling The com
Page 129 and 130: 6 Safe Refrigerant Handling • Nev
Page 131 and 132: 6 Safe Refrigerant Handling Safe ha
Page 133 and 134: 6 Safe Refrigerant Handling leak de
Page 135 and 136: 6 Safe Refrigerant Handling • Lea
Page 137 and 138: 6 Safe Refrigerant Handling Storage
Page 139 and 140: 6 Safe Refrigerant Handling Recomme
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6 Safe Refrigerant Handling 3 - Sho
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Glossary Glossary Absolute pressure
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Glossary Fossil fuels Carbon-based
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Glossary hole in late 1985, governm
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Glossary Sealed system A refrigerat
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Acknowledgements Acknowledgements I
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Copyright Copyright © United Natio
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