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BASIC REFRIGERATION & CHARGING PROCEDURES

BASIC REFRIGERATION & CHARGING PROCEDURES. SECTION ONE. REFRIGERANT PRESSURES, STATES & CONDITIONS. Load out to ambient. Load in from house. Heat flows from hot to cold. Evaporator Side Terms. Evaporating Pressure. Low Side Pressure. Suction Pressure. Back Pressure.

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BASIC REFRIGERATION & CHARGING PROCEDURES

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  1. BASIC REFRIGERATION & CHARGING PROCEDURES

  2. SECTION ONE REFRIGERANT PRESSURES, STATES & CONDITIONS

  3. Load out to ambient Load in from house

  4. Heat flows from hot to cold.

  5. Evaporator Side Terms • Evaporating Pressure • Low Side Pressure • Suction Pressure • Back Pressure

  6. Condenser Side Terms • Condensing Pressure • Head pressure • High side pressure • Discharge pressure

  7. Compressor • Pumps refrigerant vapor only! • Divides low and high side.

  8. Discharge Line • Connects the compressor to the condenser.

  9. Condenser • Rejects heat from the refrigerant.

  10. Liquid Line • Supplies liquid refrigerant from the condenser to the metering device.

  11. Metering Device • Controls the flow of refrigerant. • Divides low and high side.

  12. Evaporator • Absorbs heat into the refrigerant. • Removesmoisture from the air

  13. Suction Line • Returns superheated vapor from the evaporator to the compressor

  14. Receiver • An accessory added in the liquid line to store refrigerant for different loads placed on the system.

  15. CONDENSER Temperatures Pressures States

  16. CONDENSER INLET  • High Pressure • High Temperature  • Superheated Vapor • Saturation Point  (vapor changing to a liquid as heat is removed) • Near Ambient Temperature • High Pressure  • Subcooled Liquid OUTLET 

  17. EVAPORATOR Temperatures Pressures States

  18. Evaporator inlet  Low Pressure Low Temperature About 80% Liquid, 20% Vapor Saturated vapor  (Temperature in which liquid is changing to a vapor) • Low Pressure Low Temperature Superheated Vapor  Evaporator Outlet

  19. SECTION TWO SUBCOOLING & SUPERHEAT

  20. Subcooling and Superheating The concepts of subcooling and superheating are the two most important principles that the service technician must understand before attempting to systematically troubleshoot hvac/r systems.

  21. 210 psig = 105 ºF -100 ºF Subcooling 5 ºF R-22 Condenser Subcooling

  22. TOTAL SUBCOOLING 210 psig = 105 ºF -95 ºF Subcooling 10 ºF

  23. Superheat Superheat is any heat added to completely saturated vapor that results in a rise in temperature (sensible heat change) of the gas.

  24. 60 °F 76 psig = 45 °F 15 °F superheat Evaporator Superheat

  25. Total or System Superheat Suction line Temperature 60°F 76 psig = 45°F Superheat 15°F

  26. SECTION THREE METERING DEVICES

  27. Thermostatic Expansion Valve CapillaryTube Automatic Expansion Valve Fixed –Bore Piston

  28. CapillaryTubes • Low Cost device • Have no moving parts • Can be used on a wide range of applications

  29. Thermostatic Expansion Valve • Most efficient • Maintains a constant evaporator superheat • Helps prevent compressor flooding

  30. TXV Types • Pressure Limiting • Balance Port • Externally equalized • Internally Equalized • Electric operated

  31. TXV Bulb Placement

  32. TXV External Equalizer Tap Location

  33. Automatic Expansion Valves • Maintain a constant evaporator pressure • Used on small systems which have constant loads

  34. Fixed-Bore Metering Devices • Most common today on Residential systems • Dual purpose device Works as metering a device Works as a check valve • Critical charge

  35. SECTION FOUR System CHARGE

  36. Is The Refrigerant Charge Correct? • All refrigeration systems differ in the amount of charge they hold. • There are guidelines, charts, and techniques to follow. • System design & layout must be known

  37. How long & what size is the line set? What’s the volume of the filter drier?

  38. TXV CHARGING RULES 1. Charge system under a high load 2. Charge as a liquid when possible 3. Throttle liquid blends into low side 4. Record evaporator & compressor superheat & Condenser subcooling

  39. AIRCONDITIONING SYSTEMS Capillary Tube or Fixed Orifice #1 Weigh in the correct charge #2 Manufacture's charging charts #3 Use system superheat method

  40. Requirements for system superheat charging • Proper evaporator air flow • Accurate remote bulb temperature tester • Accurate gauge manifold set

  41. What should the Superheat be?   

  42. System Superheat Suction line Temperature 60 °F 76 psig = 45 °F Superheat 15 °F

  43. AIR FLOW Can be measured in many ways 1. Equipment data charts 2. Air flow meters 3. Combination of meter readings and formulas

  44. Sensible Heat Formula Sensible heat BTU’s CFM = 1.08 X temperature difference

  45. Sensible Heat Formula Electric Heat BTU’s = Heater amps X volts X 3.41 Sensible heat BTU’s CFM = 1.08 X temperature difference

  46. Sensible Heat Formula 3 Phase Electric Heat BTU’s = Heater amps X volts X 3.41 X 1.73 Sensible heat BTU’s CFM = 1.08 X temperature difference

  47. Sensible Heat Formula Fossil Fuel Heat BTU’s = Heater input X Efficiency or Bonnet capacity Sensible heat BTU’s CFM = 1.08 X temperature difference

  48. Measuring Duct Velocity CFM = Velocity X Area in square feet

  49. SAMPLE QUESTIONS

  50. The high and low pressures in a refrigeration system are separated by: a.       The compressor. b.      The evaporator. c.       The metering device. d.      The filter drier. The metering device.

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