Core Section Environmentally Safe Refrigerant Service Tips Techniques
- Slides: 31
Core Section Environmentally Safe Refrigerant Service Tips & Techniques Week 3 Refrigeration Principles © 2018 Mainstream Engineering Corporation Qwik System Flush®, Qwik. Check, Qwik. Injector®, Qwik-SF®, Qwik. Shot®, are registered trademarks and Qwik 609™ and Qwik. Products™ are trademarks of Mainstream Engineering Corporation, Rockledge, Florida. 1
Class Agenda } Refrigeration Principles } Quiz: Ozone Depletion and Clean Air Act Here’s what’s happening this week. 2
Refrigeration Principles } } } System Components How Refrigeration Works Types of Compressors Required Tools Good Service Practices Here’s what you’ll learn about refrigeration principles. 3
Refrigeration Principles What is cooling? } Adding heat to an object heats the object } Removing heat from an object cools the object } Heat always flows from hot to cold } To remove heat from an 80 F house the air in the house has to blow over some surface cooler than 80 F. } Surface must be even colder (below the Air’s Dew point) to remove moisture Removing heat cools an object 4
Refrigeration Principles System Components } Compressor } Expansion valve or throttling device } Condenser } Evaporator 5
Refrigeration Principles How Vapor Compression Refrigerant leaves Systems Work in the condenser as a 9 Easy Steps high-pressure liquid. 1. Compressor compresses the entering refrigerant vapor 2. Refrigerant vapor exits the compressor at a higher pressure 3. At condenser, high pressure refrigerant vapor condenses into liquid, rejecting heat 4. Liquid refrigerant travels to the filter dryer to be filtered and have water and acid removed 6
Refrigeration Principles 5. Liquid refrigerant enters the throttling device, where pressure is dropped 6. Refrigerant exits throttling device as liquid-vapor mixture and enters the evaporator 7. In the evaporator, the refrigerant absorbs heat, changing to a vapor and providing cooling 8. Refrigerant exits the evaporator and flows into the compressor 9. The process repeats itself Refrigerant enters the expansion device as a liquid. 7
Refrigeration Principles System Shutdown } Refrigerant migration dilutes the oil } Compressor crankcase heater prevents oil dilution } Crankcase heaters operate when the compressor is off Crankcase heater is located on the outside can of the compressor. 8
Refrigeration Principles Types of Compressors } Fully hermetic } Semi-hermetic } Open-drive compressors typically leak from the rotating shaft seal. 9
Refrigeration Principles Fully Hermetic Compressor } Drive motor and compressor in same casing } No gasketed sealing surfaces } Typically not repairable Scroll-Type Compressor Rotary-Type Compressor Reciprocating-Type Compressor 10
Refrigeration Principles Semi-Hermetic Compressor } Drive motor and compressor in same casing } Stationary gasketed sealing surfaces } Can be repaired } Typically more costly } More durable } Heavier 11
Refrigeration Principles Open-drive Compressor } No hermetic enclosure } Rotating shaft seal – leak source } External motor is not refrigerant cooled. } Typically belt driven 12
Refrigeration Principles CAUTION Never operate a hermetic compressor when there is a vacuum in the system. Without refrigerant there is no motor cooling. 13
Refrigeration Principles CAUTION In a system-dependent recovery using a hermetic compressor, ensure that an excessive vacuum is not developed. 14
Refrigeration Principles Required Tools } Low-loss fittings } Self-Sealing } Hand valve } Gauges } Two-valve manifold } Four-valve manifold 15
Refrigeration Principles Low-loss Fittings Self Sealing } Prevent loss of refrigerant } Closed manually or automatically } Required by the EPA Hand Valve 16
Refrigeration Principles Gauge Measurement Units } High-pressure gauge } Low-pressure gauge } Compound gauge—both psig pressure and inches Hg vacuum } Deep vacuum (micron gauge) } Single absolute pressure scale psig Atmosphe ric Pressure psia Absolut e Pressur e "Hg Inches of Mercury 17
Refrigeration Principles Here’s an example } A 500 -micron vacuum level is an absolute vacuum of 0. 5 mm. Hg or 0. 01 psia } A service manifold is not accurate enough to measure a deep vacuum 18
Refrigeration Principles Pressure and Vacuum Conversion Factors From psig to psia From psia to psig From inches of mercury to millimeters of mercury absolute to inches of mercury to microns From millimeters of mercury absolute Add 14. 7 to the psig reading Subtract 14. 7 to the psia reading Multiply the inches of mercury by 25. 4 and subtract the result from 760 Subtract the vacuum in mm. Hg absolute from 760 and divide by result by 25. 4 Multiply by 1000 19
Refrigeration Principles Examples of Conversion of Vacuum Units PSIA 14. 7 psia 12. 2 psia 9. 8 psia 7. 3 psia 4. 8 psia 2. 4 psia 0. 5 psia 0. 0 psia Reading in Inches of Mercury ["Hg] 0 "Hg 5 "Hg 10 "Hg 15 "Hg 20 "Hg 25 "Hg 28. 9 "Hg 29. 9 "Hg Reading in Millimeters of Mercury Absolute [mm. Hg Absolute] in Microns 760 mm. Hg absolute 633 mm. Hg absolute 506 mm. Hg absolute 379 mm. Hg absolute 252 mm. Hg absolute 125 mm. Hg absolute 0 mm. Hg absolute 760, 000 microns 633, 000 microns 506, 000 microns 379, 000 microns 252, 000 microns 125, 000 microns 20
Refrigeration Principles Two-valve, Three-hose Manifold Gauge } Pressure displays } Gauge operation } Center port for recovery, evacuation and charging
Refrigeration Principles How can the hose on a manifold gauge become damaged? Liquid refrigerant becomes trapped in the service hose connected to the liquid charging line. 22
Refrigeration Principles Preventing Hose Damage 1. Close the valve on the refrigerant supply tank 2. Disconnect high-side lowloss fittings first 23
Refrigeration Principles Four-valve Manifold Gauge } Saves time } Reduces contaminants after evacuation } Simplifies charging 24
Refrigeration Principles Gauge Color Codes } Blue—Low pressure } Red—High pressure } Yellow—Center 25
Refrigeration Principles Pressure Ratings of Manifold Gauges What is the maximum allowable pressure to use when checking a system? } The max pressure on the gauge is not the maximum pressure of the manifold. } Old manifolds rated for max 340 psig, even though gauge reads up to 500 psia } R-410 A manifolds are rated for use up to 800 psig with 4, 000 burst pressure. } R-410 A recovery tanks rated for at least 400 psig 26
Refrigeration Principles Theoretical AC Performance Comparisona Compression ratio Compressor discharge pressure Temperature glide a. Assuming R-22 2. 66 226 psig R-407 C 2. 83 241 psig R-410 A 2. 62 364 psig 0 F 9 F 0 F 110°F condenser, 45°F evaporator, 5°F subcooling, 15°F superheat 27
Refrigeration Principles Comparison of Saturation Pressure of Common 400 -series Blends 28
Refrigeration Principles Good Service Practices for Conserving Refrigerant } } Recover or recycle refrigerant Keep the system tight Find and repair leaks Always install a new filter-drier any time the refrigerant circuit is opened. 29
Refrigeration Principles Good Service Practices for Conserving Refrigerant } Use a pressure decay test, not a vacuum to test for leaks } Check for acid and moisture in systems } Clean & flush the system after a burnout } Draw a deep vacuum of at least 500 microns before recharging. 30
Clean Air Act More Good Service Practices for Conserving Refrigerant } Do not flush system with liquid refrigerant to clean field tubing } Never use liquid nitrogen to purge a system and always use a pressure regulator on the nitrogen gas cylinder } Use Quick. Shot acid treatment when acid is detected 31
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