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Methods of Refrigerant Recovery

The following is an excerpt taken from the RSES publication Refrigerant Usage Certification—A Study Guide for Service Technicians, which covers numerous aspects and provides information pertaining to questions asked in the EPA-608 certification exam. The book is available at the RSES Online Store.
 
Recovering refrigerant is the first step in preventive maintenance or repair of equipment. Simply put, recovery means transferring the system’s refrigerant into a refillable refrigerant cylinder. If the refrigerant was not contaminated by a hermetic motor burnout or other cause, it may be of adequate quality to be charged back into the system after repairs are completed. Or, the recovered refrigerant may require further processing before it can be returned to the system. This may mean on-site recycling or off-site reclaiming.
Remember that recovery and recycling equipment manufactured on or after November 15, 1993 must be tested by an EPA-approved testing organization to ensure that it meets EPA requirements. Equipment that was manufactured before November 15, 1993, does not need to be certified by an EPA-approved testing organization, even if it was purchased after that date. When you buy equipment, be sure to check the date of manufacture. Also check that equipment manufactured before the 1993 date can achieve the required vacuums required by EPA regulations.
Recovery and recovery/recycling equipment comes in a variety of designs:
•           One type removes liquid only.
•           A second type removes refrigerant in vapor form only.
•           A third type removes both liquid and vapor, but does not separate the system oil from the refrigerant. (It goes into the storage cylinder exactly as it was in the system.)
•           A fourth type removes liquid and vapor and separates system oil.
 
Each of these has advantages and disadvantages. The liquid-only recovery is fast, but it leaves vapor in the system. The vapor-only unit removes all of the refrigerant, but is considerably slower. Recovery machines that separate the refrigeration or air conditioning system’s oil from the refrigerant are not necessarily better than those that do not. The primary difference is the disposition of the oil. Reclaimers charge for the disposal of the used oil, and some states and municipalities have regulations that the user must follow.
The process of recovering refrigerant is similar regardless of the equipment used. The best place to start is with proper equipment. Manifolds should be in good condition with no leaks. Hoses that are non-permeable are preferred. At the very least, they should have tight fittings.
Some recovery units require evacuation before each use. Many need to be evacuated when a different refrigerant is being recovered—for example, when you are repairing an R-12 system after an R-22 system. If only a storage cylinder is used, it must be evacuated to at least 1,000 microns.
Once the initial set-up has been completed, recovery can begin. Generally, the procedure follows these basic guidelines: A hose is connected from a service valve on the system being repaired to the inlet of the recovery system. The hose should be as short as possible to reduce pressure drop, refrigerant emissions, and recovery time. The location of the service valve depends on the type of machine. Once the refrigerant has traveled through the machine, it is transferred into the refillable storage cylinder. If the recovery unit does not separate the oil, the refrigerant is ready to send on to a reclaiming station. If the oil is separated, drain and handle it according to local legislation.
 
Caution: Never mix refrigerants in a recovery vessel. This may render the refrigerant impossible to reclaim.
 
 
Procedures
Empty recovery cylinders must be completely evacuated before being filled. This avoids contamination of the recovered refrigerant by air, moisture, or remaining traces of other refrigerants. Evacuate to a minimum of 1,000 microns.
For a faster and more efficient recovery, chill the refillable cylinder and keep it cool during the procedure. This can be done by setting the cylinder in a bucket of ice. There are also dry chemicals on the market that can be mixed with water to create low temperatures. The mixture is then poured into the bucket in which the cylinder is immersed during the transfer process. The lower temperature of the cylinder reduces the pressure of the refrigerant inside it. Conversely, if the system from which you are removing refrigerant is at a low ambient temperature, the recovery process will be slower.
Before beginning recovery, check the positions of all service valves and the oil level of the recovery unit. Recover the refrigerant into the system’s own receiver or storage tank if it has one. It is most efficient to recover liquid first (from the system’s liquid line), then vapor. Recovering refrigerant in vapor phase will leave the oil in the system, minimizing oil loss.
When recovering from small appliances, first identify the refrigerant that you are about to recover. Older refrigerators, particularly those built before 1950, may contain non-fluorocarbon refrigerants, which must not be recovered with current recovery equipment. The same is true of many recreational vehicle appliances, both old and new. When access fittings need to be installed, they should be checked for leaks. Follow these guidelines when using system-dependent (passive) recovery equipment:
•           If the appliance compressor does not run, warm the compressor oil and tap the compressor. This will help release refrigerant trapped in the oil.
•           If the appliance compressor does not run, recover refrigerant from both the high and low sides of the system for a complete recovery. This will also speed the recovery process.
•           If the appliance compressor is operable, run it and recover the refrigerant from the high side.
 
When recovering refrigerant from chillers, maintain water circulation in order to prevent freezing.
Slight amounts of refrigerant may escape during these procedures, but U.S. Federal regulations state that “de minimis (minimal) releases associated with good faith attempts to recapture and recycle or safely dispose of any such substance (refrigerant) shall not be subject to the prohibition” (against venting).
[To read more on proper safety procedures, the refrigeration cycle, differences and requirements for different certification types (Core; Type I; Type II; Type III; Universal), and more, pick up the 75-page book Refrigerant Usage Certification—A Study Guide for Service Technicians.]
 
 
 
 
 
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Beginning with basic theory and extending to complex troubleshooting, training courses covering refrigeration and air conditioning, heating, electricity, controls, heat pumps and safety may be conducted in a classroom environment or though self study. RSES publications may be purchased by schools, contractors, manufacturers or any other industry group wanting to conduct comprehensive training programs. Seminars covering air conditioning troubleshooting, electrical troubleshooting, compressor training, condenser training, refrigerant piping practices, DDC controls, and more are held in various cities across North America.

Select training programs offer Continuing Education Units (CEUs) and NATE Continuing Education Hours (CEHs).

In addition, RSES offers industry certification preparation materials for refrigerant handling (EPA Section 608), R-410A and North American Technician Excellence (NATE) examinations.

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