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

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4 Servicing Practices Liquid refrigerant charging Liquid refrigerant charging is the process of moving liquid refrigerant from the liquid space of the refrigerant cylinder to the liquid side of the system, as shown here: Liquid refrigerant charging usually applies to high refrigerant charge systems, like large commercial systems and systems with liquid receivers. Charging liquid refrigerants always requires skill and caution. 100 PSIG Liquid refrigerant charging 20 PSIG CRACKED 40 PSIG CRACKED OPEN 196 PSIG CLOSED The suction hand-valve is to be used carefully to monitor the liquid gauge pressure to not exceed 140 kPa (approximately 20 psig) above suction pressure; when the blue hose (suction line) frost is observed close to the hand-valve, check the suction pressure. Repeat until the desired charge is obtained. CRACKED Remember always to make sure that: • If the refrigerant cylinder does not have a dip-tube, it should be placed in an upside down position to guarantee liquid flow. • Bypassing the low-pressure side control to avoid shutting off during charging. 106
4 Servicing Practices Why charge refrigerant blends as liquids? Refrigerant blends are simply a mixture of different refrigerant components. If the blend is a zeotropic mixture (i.e. R4xx) and it is charged as vapour, the refrigerant with the highest vapour pressure will be charged at a higher proportion than the other component(s). Charging as a liquid is the only way to guarantee that the blend is charged within its intended composition. Fractionation of a refrigerant blend (separation of the individual components) can occur by removing the refrigerant from the cylinder as a vapour instead of a liquid. This can potentially lead to both safety and performance issues. As such, it is recommended charging all blends in liquid phase only. From a safety standpoint, a blend with an A1 safety classification – that has been composed of non-flammable and flammable substances – will remain nonflammable, even after fractionation has occurred. Performance may be significantly affected, depending on the extent of fractionation. If only a small amount of the refrigerant placed into the system was charged as vapour, the blend may perform adequately. The performance of systems containing larger percentages of a blend charged as vapour is more likely to be affected by fractionation. Typically, more of the high-pressure components will be found in the system, and less in the cylinder. Additionally, the refrigerant remaining in the cylinder may also be compromised. In these cases, it is recommended contact technical support of the refrigerant supplier. It is also important to note that if the entire contents of a refrigerant blend container (full cylinder) are charged into a system as vapour, it will produce the same effect as charging the entire cylinder as liquid. Also, certain refrigerant blends are more susceptible to fractionation than others, and their stated temperature glide provides an indication of this. For example, fractionation is a greater concern when working with R409A (high temperature glide, ~ 8 K) than when working with R410A (a small glide, < 1 K). 107
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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
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2 Refrigerants Types of refrigerant
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2 Refrigerants Those with ozone dep
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2 Refrigerants Those with zero ozon
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2 Refrigerants Carbon dioxide (CO2,
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2 Refrigerants Azeotropic Blends An
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2 Refrigerants Using Refrigerant Bl
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2 Refrigerants Lubricants Today, al
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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 and 90: 4 Servicing Practices Non-condensab
Page 91 and 92: 4 Servicing Practices Evacuation A
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: 4 Servicing Practices Electronic ch
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
Page 141 and 142: 6 Safe Refrigerant Handling 3 - Sho
Page 143 and 144: Glossary Glossary Absolute pressure
Page 145 and 146: Glossary Fossil fuels Carbon-based
Page 147 and 148: Glossary hole in late 1985, governm
Page 149 and 150: Glossary Sealed system A refrigerat
Page 151 and 152: Acknowledgements Acknowledgements I
Page 153: Copyright Copyright © United Natio
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