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Improved Evacuation and Charging Methods for Refrigeration Systems

Learn about the importance of removing moisture from refrigeration systems through proper evacuation techniques and the use of high vacuum pump technology. Discover the impact of moisture on system components and how to achieve a deeper vacuum for optimal system performance. This guide provides valuable information and tools to improve the evacuation and charging process.

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Improved Evacuation and Charging Methods for Refrigeration Systems

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  1. …just got better

  2. Evacuation / ChargingSuperheat and SubcoolingCharging Methods 2007

  3. Evacuation

  4. Moisture In A Refrigeration System • Visible Moisture • Water Droplets • Uncommon, but it can occur • Invisible Moisture • Water Vapor • Found in all gasses • Found in all solids

  5. Visible Moisture Problems • Freeze Ups • Ice crystal formation will occur at the point of expansion, i.e.: • Capillary Tube • TXV • Flow Rator • This problem will be intermittent • When the system warms up the problem stops

  6. Invisible Moisture • Air in the piping • “Wet” Refrigerant • Leaks Under a Vacuum Condition • Copper and Brass Components • System Components exposed to the atmosphere during assembly

  7. Invisible Moisture • Causes Corrosion • Moisture Will React With The Metals Metal + H2OCorrosion

  8. Moisture & Refrigerant Moisture + RefrigerantAcid

  9. Moisture & Refrigerant • CFC & HCFC & HFC • Hydrolyze to form Hydrochloric Acid • Hydrofluoric Acid • Acid Formation Is Accelerated By Heat • Copper and Brass Will Be Attacked • Plates Hot Surfaces • Bearings Seize

  10. Copper Plating

  11. Moisture & Refrigerant & Oil Metal + Refrigerant + Acid + Oil Sludge

  12. So How Do We Get The Water Out? • We Boil It • We Can’t Raise The System Temperature To 212°F • So We Have To Lower the System Pressure To A Point Where Water Boils At Ambient Temperatures.

  13. Pressure vs. Boiling Point • Physics 101 • As The Pressure is Decreased - The Boiling Point Decreases • To Decrease The Pressure, We Could Raise The System To A Higher Altitude. • There Is Less Atmosphere Above Us On Pike’s Peak • Less Weight Of Air = Lower Air Pressure

  14. Pressure vs. Boiling Point • At Sea Level • Atmospheric Pressure = 14.7 PSI. • Boiling Point = 212° F • On Pike’s Peak (14000 + Elevation) • Atmospheric Pressure = 8.32 PSI. • Boiling Point = 184° F • This Is Still Not Low Enough

  15. Pressure vs. Boiling Point • To Boil Water @ 80°F • The pressure has to be lowered to 28.92 inches of mercury • To Boil Water @ 45°F • The pressure has to be lowered to 29.62 inches of mercury vacuum or 7620 microns

  16. What The Heck Is A Micron? • 1 Inch = 25400 Microns • .039 Inch = 1000 Microns = 1 Millimeter • 1 Micron = 1/1,000,000 meter • To Small To Measure With A Gauge.

  17. How Is Vacuum Measured? Each Mark Represents 2” of Water Column Or 50800 Microns

  18. How Is Vacuum Measured? • A Compound Gauge • Impossible To Determine • A Vacuum Gauge • The Resolution Is Not Suitable • Readings Change with Altitude (pressure) • A U-Tube Manometer • Resolution Is 1 MM of Mercury (That Equals 1000 Microns)

  19. How Is Vacuum Measured? • A Thermister Micron Gauge • Will Measure The Last Inch Of Vacuum • Atmospheric Pressure Has No Impact • High Resolution Readings Are Possible • Readings Go Down To 1 Micron

  20. How Is Vacuum Measured? • Will accurately measure vacuum level in 10 segments from 25,000 to 50 Microns. • The LCD screen can be read even in direct sunlight and is designed to minimize battery consumption. • The durable carrying case protects the instrument and has a built-in compartment for storing the 24" charging hose (included).

  21. How Is Vacuum Measured?Other Tools of the Trade • Displays pressure in microns in steps of 1 micron. Has pump down indication showing progress from atmospheric pressure. • Range: 50 to 2000 microns of mercury. • Resolution: 1 micron of mercury. • Pump down indication: when pumping down from atmospheric pressure to 2000 microns, output of head goes from over 3VDC to 2VDC. • Straight-in access to sensor for easy cleaning. • Fitting: 1/4" flared brass fitting (male) . • Accuracy (@~75ºF): ±10%, 0-1000 microns of mercury. • Auto-off can be disabled for data logging. • "T" for inline vacuum testing.

  22. Thermistor Micron Gauge • This Gauge Measures The Thermal Conductivity Of The Gas Remaining in the Refrigeration System • It Has A Source Of Heat • It Has A Heat Receptor • The Thermistor

  23. Thermistor Micron Gauge Hose to System Heat Source Thermistor The more gas left---- The higher the Temperature on Thermistor

  24. Thermistor Micron Gauge Hose to System Heat Source Thermistor Less Gas……..Less Heat Received….Lower Reading

  25. Vacuum Pumps • The Air Compressor Type • It Does Move Large Volumes Of Air • It Cannot Achieve a Deep Enough Vacuum • It Can Achieve At Best 28” of Mercury Vacuum • No Water Would Be Boiled

  26. Vacuum Pumps • The Piston Compressor Type • At Best, It Can Achieve 29” Of Mercury Vacuum (at Sea Level) • That Will Not Boil Water Under 80F • The Rotary Compressor Type • It Can Achieve A 29.63” Of Mercury Vacuum (at Sea Level) • Water Would Boil @ 45F • It Is, However, Unsuitable For Systems Larger Than Household Refrigerators

  27. High Vacuum Rotary Vane Pumps • Single Stage • It’s Smaller • It’s Light Weight • It Pulls Down To 1000 Microns • Robinair Will Pull Down To 200 Microns

  28. Single Stage

  29. High Vacuum Rotary Vane Pumps • Two Stage Vacuum Pumps • The Most Commonly Used Vacuum Pump For Service • It Has A Larger CFM Capacity • It Is Slightly Heavier Than The Single Stage Vacuum Pump Of The Same Capacity • It Can Achieve A Deeper Vacuum Than The Single Stage Vacuum Pump Because The Second Stage Takes Over At The Point The 1st Stage Stops

  30. High Vacuum Rotary Vane Pumps • Two Stage (cont..) • These Vacuum Pumps Can Pull Down To One Micron • Robinair Guarantees Its Pump To Pull Down To 20 Microns

  31. Two Stage Vacuum Pumps

  32. Two Stage Vacuum Pumps ISO Valve 2nd Stage 1st stage

  33. Rotor & Vanes • Notice The Off Set Construction • The Vanes Come Out At Low RPM To Wipe The Interior Of Pump • The 1st Stage Vanes Are Ceramic, The 2nd Stage Vanes Are Aluminum

  34. Gas Ballast Valve • Mixes Dry Air With High Humidity Air • Reduces Moisture That Is Condensed Into The Oil • Makes Oil Last Longer

  35. Gas Ballast Valve • Open The Valve At The Beginning Of The Evacuation Process • When A level Of 1000 Microns Is Achieved, Close The Valve

  36. The Size of The System The Complexity of The Piping The System Components Oil Separators Accumulators Valves The Size of Vacuum Pump How You are Hooked Up To the System High & Low Side The Size of Hoses Access Fitting? The Ambient Temperature Issues That Affect TheSpeed Of Evacuation

  37. Speed Of Evacuation • Use The Largest Hoses You Can • Add Heat To Areas Of Restriction • Get the Access Fittings Out Of The Way • Measure The Vacuum At The System • Isolate The System And Equalize It To Get A True Reading

  38. Access Core Removal Tool

  39. How Much PumpDo You Need? • Vacuum Pumps Are Rated In Cubic Feet Per Minute Of Free Air Through the Pump • As A Rule Of Thumb • 1 CFM Per 7 Tons Of System Is Adequate • I.E. A 6 CFM Rated Pump Will Be Good For 42 Tons Of System Capacity • Multiple Pumps Are OK

  40. Evacuation Set Up

  41. Evacuation WithMicron Gauge

  42. CONDITIONS THAT AFFECT CHARGING ACCURACY

  43. CHECK THE AIR FLOW • MAKE SURE THE FILTERS ARE CLEAN • ASSURE THAT THERE ARE NO RESTRICTIVE FILTERS IN PLACE • IS THE BLOWER WHEEL CLEAN? • IS THE EVAPORATOR COIL CLEAN? • VERIFY THAT YOU HAVE 400 CFM’s OF AIRFLOW PER TON

  44. METERING DEVICES – Fixed Orifice (Capillary)

  45. METERING DEVICES – Fixed Orifice (Flowrator / Orifice) Orifice Metering Device

  46. METERING DEVICES - TXV

  47. TEMPERATURE PROBETEST POINT LOCATIONS • SUCTION LINE SERVICE VALVE • LIQUID LINE SERVICE VALVE

  48. SATURATION POINT THE TEMPERATURE AT WHICH AT A GIVEN PRESSURE, THE REFRIGERANT IS NEITHER 100% LIQUID NOR 100% VAPOR IT IS THE POINT WHERE THE REFRIGERANT IS CHANGING STATE FROM LIQUID TO VAPOR OR VAPOR TO LIQUID

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