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Learn to maintain, service, retrofit, and handle refrigerants effectively with this comprehensive guide. Discover preventive maintenance and A/C service operations to keep systems running smoothly.
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CHAPTER 15 Refrigerant Service Operations
OBJECTIVES After studying Chapter 15, the reader will be able to: • Be familiar with the preventive maintenance operations and the adjustments necessary to keep heating and A/C systems operating properly. • Perform basic A/C service operations, given the operating manual for the equipment. • Be familiar with how to retrofit R-134a into an R-12 system. • Be able to complete the ASE tasks related to refrigerant handling.
Black death Charging cylinder Conversion fitting Cubic feet per minute (cfm) Electronic scales Evacuate Fingerprint Flush Identifier Inline filter Live flushing Micron Noncondensable gases (NCG) Out-gases Partial charge Pressure-temperature (PT) Recover Recycle Retrofit Slugging Tank certification Topping off KEY TERMS
INTRODUCTION • The service and repair of heating and A/C systems consist of preventive maintenance operations; the adjustment, repair, overhaul, or replacement of system components; and standard A/C service operations.
INTRODUCTION • There are several important facts to keep in mind when servicing an A/C system: • A/C systems are designed to operate using a specific amount of a particular refrigerant. • A/C systems are designed to operate using a specific amount of a particular refrigerant oil. • Adding any other chemical into a system can create a chemical problem that can cause system damage or failure. • GAUGE PRESSURES
PREVENTIVE MAINTENANCE AND ADJUSTMENT OPERATIONS • The U.S. Clean Air Act has placed a group of requirements on A/C service. • These requirements can be viewed at www.epa.gov/ozone . • A/C SERVICE AND THE CLEAN AIR ACT
A/C SERVICE OPERATIONS • REFRIGERANT CONTAMINATION • SEALANT CONTAMINATION • REFRIGERANT IDENTIFICATION • SEALANT IDENTIFICATION • REFRIGERANT RECOVERY • RECOVERING CONTAMINATED REFRIGERANT • RECYCLING REFRIGERANT • AIR CONTAMINATION CHECKS
TECH TIP • A special filter called the Recycle Guard is available that can be attached to the inlet hose of the recovery machine. The Recycle Guard filter is designed to remove contaminants such as sealants and dye before they can enter the recovery unit.
A/C SERVICE OPERATIONS • FLUSHING AN A/C SYSTEM • INSTALLING AN INLINE FILTER • CHECKING AND CORRECTING OIL LEVELS • OIL INJECTION, CHARGING CHOICES • EVACUATING A SYSTEM • RECHARGING A SYSTEM • PARTIAL CHARGING • CHARGING FROM LARGE CONTAINERS • CHARGING FROM SMALL CANS
TECH TIP • The compressor in an orifice tube system is cooled by liquid refrigerant that passes through the oil bleed hole in the accumulator. An undercharged system will cause compressor overheating and probable failure. • An overcharged system will cause higher-thannormal high-side pressure, especially if the vehicle is in stop-and-go traffic on a hot day. Excessive pressure can cause the high-pressure cutoff switch to shut down the system.
TECH TIP • The specified charge in an orifice tube system can produce higher duct temperatures than an undercharge. • Professional service technicians prefer not to top off a system because the system probably has a leak that should be repaired. Also, the system contains an unknown amount of refrigerant, oil, and possible contaminants. It is a much better practice to recover the refrigerant and see how much refrigerant and oil come out. The refrigerant can now be recycled to remove any air that might have been present and then returned to the system along with additional refrigerant to fill the system with the specified amount of clean oil.
TECH TIP • Some technicians prefer to begin the charging process into the high side (system off). The highside pressure should increase immediately as the valve is opened. There should be a slight delay and a slower low-side pressure increase as refrigerant bleeds through the TXV or OT. A pressure increase that is too rapid indicates a possible compressor internal leak; too slow an increase indicates a possible restriction of the TXV or OT.
TECH TIP 2. Some technicians prefer to complete the charging process with the system operating so they can watch the gauge pressures and temperatures normalize, even though this is not necessary with most modern charging stations. Normal A/C system operation should occur about 1/4 to 1/2 lb before the system is completely charged. This last volume becomes reserve to be stored in the receiver–drier or accumulator. At this point, the sight glass should clear up or the bottom of the accumulator should become cold. The highside pressure should not increase as the remaining refrigerant is charged into the system.
TECH TIP • The charging operation should be done with the can vertical, charging vapor, but it can be safely speeded up by rotating the can to horizontal and then back to vertical. This increases can pressure by adding heat to the refrigerant. • Any refrigerant remaining in the can, sometimes called the heel or tail, often evaporates to become a contaminant in the atmosphere. There is also a loss from the hose as the cans are changed. • When a can empties, allow the low-side pressure to drop as low as it will go to pull as much refrigerant as possible from the can. It is easy to leave as much as an ounce in the can, and this can cause an undercharged system or one without any refrigerant reserve.
TECH TIP 4. Tampering has become a major concern with many A/C service technicians; once a system has been serviced and put in proper operating condition, they want it to stay that way. A set of seals has been developed so it is easy to tell if a system has been opened. These seals are plastic sleeves that are placed over the service fittings and heated to shrink them to fit the fitting and cap. Another type of service port seal is similar to an electrical tie wrap, and installs without the need of a hot air gun. The seal must be cut in order to remove the service cap.
RETROFITTING R-134A INTO AN R-12 SYSTEM • Retrofitting is normally a repair-driven operation; it is not done until absolutely necessary. • All experts agree that if a system was designed for R-12, R-12 should be used in it when it requires service, even though some systems cool better after changing to R-134a.
RETROFITTING R-134A INTO AN R-12 SYSTEM • REFRIGERANT CHOICE FOR RETROFIT • POSSIBLE RETROFIT PROBLEMS • RETROFIT PROCEDURE
USING AND INSTALLING SEALANTS AND STOP LEAKS • Most HVAC technicians dislike stop leaks as they are considered an inadequate or temporary repair method, and the best repair is to actually fix the leak. • Sealants/stop leaks might or might not work, and they might or might not damage the system.
SUMMARY • A major maintenance operation is to ensure the system has a good accessory drive belt that is properly adjusted. • The first refrigerant service operation is to identify the refrigerant in the system and check to make sure that it does not contain a sealant. • The refrigerant is recovered from a system so that service operations can be performed. • A Recycle Guard filter can remove contaminants from refrigerant being recovered. • Recycling removes foreign particles, water, and air from refrigerant.
SUMMARY • Sections of an A/C system can be flushed or a filter can be installed to remove foreign particles. • Most vacuum pumps require periodic oil changes so they can do an effective job in removing air and other non-condensable gases. • Starting with the system in a vacuum, the specified amount of new or recycled refrigerant is charged into the system. • Most professional technicians do not use small cans to charge a system. • An R-12 system can be retrofitted to R-134a using an approved retrofit procedure.
REVIEW QUESTIONS • A dirty condenser with debris at the front can be cleaned using ______________ ______________ , ______________ ______________ , or a(n) ______________ . • The first step in any refrigerant service procedure should be to ______________ what type of ______________ is in the system. • More than ______________ ______________ air in the refrigerant of an A/C system is considered contaminated. • Refrigerant contaminated with air should be ______________ and then ______________ . • A shop that does full refrigerant service on both older and newer A/C systems must have ______________ sets of service ______________ . • A recycling machine has the ability to remove ______________ , ______________ , ______________ , and solid ______________ from the refrigerant.
REVIEW QUESTIONS • Refrigerant that is contaminated with air will have a(n) ______________ that is ______________ than normal for a particular temperature. • A(n) ______________ or ______________ should never be flushed, and it is doubtful that a flat-tube ______________ can be cleaned by flushing. • A(n) ______________ ______________ can be installed in the liquid line to trap debris that can plug the OT. • Water is removed from inside an A/C system by ______________ the system to a(n) ______________ lower than the boiling point of water. • The ______________ in most vacuum pumps must be ______________ periodically in order to keep the pump operating properly. • Partial charging of a system is not recommended because of the difficulty of adding the ______________ ______________ of refrigerant.
REVIEW QUESTIONS • The proper charge amount for a vehicle can be found on the ______________ under the vehicle’s ______________ . • It will take ______________ small (12 oz) ______________ of refrigerant to charge a system that holds 2 1/4 lbs of refrigerant. • If retrofitting an R-12 system to R-134a, a small refrigerant leak will become ______________ , and high-side pressures will probably ______________ . • If retrofitting a system that contains a high-pressure relief valve, a(n) ______________ ______________ ______________ ______________ must be installed. • When retrofitting a system, new ______________ ______________ must be permanently installed over the existing ones, and a(n) ______________ ______________ must be filled out and placed over the old one.
CHAPTER QUIZ 1. Technician A says that eye protection should be worn when working with refrigerants. Technician B says to avoid skin contact with refrigerants and their oil. Who is correct? • A only • B only • Both A and B • Neither A nor B
CHAPTER QUIZ 2. Two technicians are discussing how to remove refrigerant from a system. Technician A says that you can vent it into the atmosphere as long as it has moisture in it. Technician B says that all refrigerant must be captured. Who is correct? • A only • B only • Both A and B • Neither A nor B
CHAPTER QUIZ 3. Technician A says that the same recovery unit can be used for R-12 and R-134a. Technician B says that the service hoses from an R-134a recovery unit must have shutoff valves within 18 inches of the end. Who is correct? • A only • B only • Both A and B • Neither A nor B
CHAPTER QUIZ 4. Technician A says that high pressure in recycled refrigerant is only caused by air contamination. Technician B says that recycled refrigerant should have the same purity standards as new refrigerant. Who is correct? • A only • B only • Both A and B • Neither A nor B
CHAPTER QUIZ 5. Technician A says that compressor failure sends metal and debris through the system, so it should be flushed using R-11. Technician B says that a good method to solve this problem is to replace the compressor and install an inline filter. Who is correct? • A only • B only • Both A and B • Neither A nor B
CHAPTER QUIZ 6. A system contaminated with moisture should be evacuated for a minimum of 15 minutes. • True • False
CHAPTER QUIZ • Technician A says that checking the pressure–temperature relationship is a reliable way to check for contaminated refrigerant. Technician B says that refrigerant with more than 2% of a foreign refrigerant normally should be sent off for reclaiming or disposal. Who is correct? • A only • B only • Both A and B • Neither A nor B
CHAPTER QUIZ 8. Refrigerant can be contaminated with NCG if the ______________ . • recovery unit hose is not tight • system is not thoroughly evacuated before recharging • technician uses sloppy service procedures • All of these
CHAPTER QUIZ 9. Technician A says that a system should be evacuated for twice as long if the vacuum pump will only pull it down to 20" Hg. Technician B says that the system might have a leak in it if it will not pull down into a deep vacuum. Who is correct? • A only • B only • Both A and B • Neither A nor B
CHAPTER QUIZ 10. Technician A says that refrigerant charge levels are given in service manuals. Technician B says that charge levels are printed on the under-hood decal. Who is correct? • A only • B only • Both A and B • Neither A nor B
CHAPTER QUIZ 11. Technician A says that an overcharge will cause excessively high system pressures. Technician B says that a small can of refrigerant holds 1 lb. Who is correct? • A only • B only • Both A and B • Neither A nor B
CHAPTER QUIZ 12. We normally charge refrigerant into the high side with the engine running. • True • False
CHAPTER QUIZ 13. Technician A says that retrofitting a system is simply a matter of recovering the R-12 and recharging it with a drop-in refrigerant. Technician B says that the charge level specification is the same with R-134a as with R-12. Who is correct? • A only • B only • Both A and B • Neither A nor B
CHAPTER QUIZ 14. Technician A says that SNAP approval indicates a good refrigerant that will have no problems in a system. Technician B says that using any refrigerant that contains R-22 requires the system to have barrier hoses. Who is correct? • A only • B only • Both A and B • Neither A nor B
