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REFRIGERATION SYSTEM

REFRIGERATION SYSTEM. Chapter 4 Classroom Manual Page 67. OBJECTIVES. Diagnose six system malfunctions by gauge readings. Identify the low and high side of the air conditioning system. Read and understand temperature-pressure charts. Discuss temperature-pressure relationships. OBJECTIVES.

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REFRIGERATION SYSTEM

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  1. REFRIGERATION SYSTEM • Chapter 4 • Classroom Manual • Page 67

  2. OBJECTIVES • Diagnose six system malfunctions by gauge readings. • Identify the low and high side of the air conditioning system. • Read and understand temperature-pressure charts. • Discuss temperature-pressure relationships.

  3. OBJECTIVES • Identify differences between CFC-12 and HFC-134a systems. • Identify differences between thermostatic expansion valve (TXV) and fixed orifice tube (FOT) systems. • Understand the proper handling of refrigerants and refrigeration oil.

  4. INTRODUCTION • Figure 4-1, (Pg 68C) shows the dividing line between low and high sides. • Low side gauge is a compound gauge. • There is a direct relationship between pressure and temperature. • Air temp flowing through evaporator will be a few degrees warmer than the freon.

  5. Low side Expansion Valve ACSYSTEM High side

  6. SYSTEM DIAGNOSIS • Knowing the ambient air temperature. • Determine normal HIGH side pressure. • There are seven conditions for A/C systems. • 1 normal condition. • 6 conditions that indicate a malfunction.

  7. NORMAL OPERATION • Low-side gauge: Normal pressure • CFC-12: 32-33 PSI • HFC-134a: 30-31 PSI • High-side gauge: Normal pressure • CFC-12: 185-190 PSI • HFC-134a: 204-210 PSI

  8. PLATE 1 • Normal refrigerant charge expansion valve system. • Receiver/ Dryer in high side of system.

  9. PLATE 9 • Normal refrigerant charge orifice tube system. • Accumulator in low side.

  10. REFRIGERANT • Refrigerant is the term used when referring to the fluid that is used in an automotive air conditioning system. • “a gas used in a mechanical refrigeration system” page 77

  11. R-12 (CFC-12) • Dichlorodifluoromehtane is CFC-12 • Safe to Humans • Can withstand high pressures without decomposing or deteriorating • Boiling Point is -21.67 degree Fahrenheit • Does not react with A/C components • Soluble in mineral oil

  12. Temperature and PressureRelationship of CFC-12 • Freon temperature and degrees Fahrenheit are roughly the same from 20 to 70 degrees. • A gauge reading of 28 PSI equals a refrigerant temperature of 30 degrees. page 78

  13. 134a • New Refrigerant to replace CFC-12. • Tetrafluoroethane (R-134a) • Is a hydroflourocarbon (HFC) • Does not contain chlorine. • Molecules are 11 times smaller so must use barrier type refrigerant hoses. page 78

  14. R-22 for LEAK TESTING • R-12 = 50psi • R-22 = 100psi • Do NOT mix refrigerants • R-22 is NOT a replacement for R-12 • Small amounts of R-22 used in leak testing can be vented to atmosphere. page 82

  15. HANDLING REFRIGERANTS • All refrigerants must be properly stored, handled, and used. • Do NOT expose containers to flame. • Burning refrigerant creates poisonous gas. • Pound cans can NOT be identified by color. • Do NOT mix refrigerants. page 82

  16. SAFETY PRECAUTIONS • Wear safety glasses or goggles at all times. • Do NOT vent freon in a confined space. • Avoid breathing these or any other fumes. • HFC-134a is combustible. • Do NOT pressure test A/C system with shop air. page 84

  17. OTHER REFRIGERANTS • Use R-12 in R-12 systems. • Use R-134a in R134a systems. • R134a is the only legal replacement for R-12 after proper retrofit procedures. page 86

  18. REFRIGERATION OIL • R-12 uses mineral oil. • R134a uses PAG oil. • Ester Oil can be used in conversions. • Small Quantities of Mineral oil can be mixed with Ester oil. • Mineral oil and PAG oil are not mixable. page 86

  19. SERVICING TIPS • A/C oil level should be checked each time the system is drained. • Keep the cap on oil container. • Refrigerant oil is hygroscopic. • Moisture is damaging to A/C system.

  20. PREVENTIVE MAINTENANCE • Inspect electrical system for A/C • Inspect Blower motor for abnormal noises, leaves in ducts, etc.. • Check Voltages • Check Compressor Clutch operation • Check Belts and A/C Hoses • A/C Function Check page 88

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