Before using the push-pull recovery method, make sure the system does not have a heat pump or a reversing valve, will allow a solid column of liquid to form, or does not have an accumulator. If any of these components exist within the system, the push-pull method can't be used. You will need to use a liquid or vapor recovery method.

Liquid recovery. With the advent of oil-less compressors and constant pressure regulator valves, liquid recovery has become the preferred method of recovery and recommended by most recovery equipment manufacturers. Liquid recovery is performed the same way as standard vapor recovery. The only difference is that you will connect to the high side of the system. Recovering liquid is ideal for recovering large amounts of refrigerant like refrigerant transfer, or if the system you are servicing will allow you to recover liquid.

After completing the transfer of liquid refrigerant between a recovery unit and a refrigeration system, avoid trapping liquid refrigerant between the service valves.

Vapor recovery: During vapor recovery, an additional hose must be attached between the storage tank and the recovery unit. Vapor is drawn from the refrigeration unit into the recovery system. It passes through the compressor to the condenser, where cooling occurs. Once cooled to a sufficient temperature, the gas turns to liquid and proceeds into the storage tank. Refrigerant recovery systems operate on a temperature pressure relationship. A lower temperature facilitates a lower pressure, allowing for fast, efficient operation.

Vapor recovery is approximately 75 to 80% of the recovery process, so it's important to use a recovery machine with a high vapor recovery rate.

Recovering Refrigerant
Before using a recovery unit you should always: check the positions of the service valve, evacuate and recover any remaining refrigerant from the unit's receiver, and evacuate an empty recovery cylinder prior to transferring refrigerant to the cylinder.

Many technicians prefer to have a digital refrigerant scale for keeping track of the refrigerant. This is recommended, for your own service records, and it will help in the event of an EPA audit request.

Recovering large amounts of liquid refrigerant can sometimes involve large amounts of oil if the system lacks an adequate oil separator. If this recovered refrigerant isn't going to be liquid-charged back into the same system, you might want to separate the refrigerant from the oil to measure the oil. That way, you'll know how much oil to charge back into the system.

When working on a system that has parallel compressors, you must remember to isolate a parallel compressor system in order to recover refrigerant. Failure to do so will cause an open equalization connection that will prevent refrigerant recovery.

Liquid can often become trapped in the refrigeration system. A good indicator of trapped liquid in a system is frost or condensation forming on the components where the liquid is trapped. If you are unable to locate the trapped liquid, but you know it's there because the recovery job is taking "forever,"then turn on the system compressor (if it's operable) for a few seconds. This will get the refrigerant moving to another part of the system and in the process pick up enough heat to boil off.

Another trick is to cool the tank, if it's partially filled, prior to or during recovery. This operation will lower the pressure in the storage tank, and therefore speed up recovery. There must be a minimum of 5 lbs. of liquid refrigerant in the tank you wish to chill. There's no magic here; you're simply using your recovery machine to make a refrigerator, where the tank is the evaporator. Five to 10 minutes of chilling produces some very dramatic tank cooling, depending on conditions. The greater the quantity of refrigerant in the tank, the longer the process will take.

Finishing the Job
After the refrigerant has been removed, and before the system is ready to receive the new refrigerant, use a vacuum pump to remove moisture and air from the system. Systems today are built tighter, so accurate charges become critical. This means these systems have a greater sensitivity to moisture and other contaminants, making thorough evacuation very important.

Most systems are not "recovery-friendly." Many lack access ports at their lowest points. Significant time can be saved, especially on maintenance contracts, by simply installing access ports at all of the lowest points in the system, where liquid is likely to accumulate. Since most systems lack such ports, you need to be prepared to boil off the trapped liquid with a heat gun.

If you're using your recovery equipment to recover multiple refrigerants, remember to purge the recovery equipment. Most new equipment includes automatic purge features, which clear out the machine, and prepare the equipment for the next job.

Safety First
Safety is always a concern when recovering refrigerant. Always wear safety glasses and gloves to keep debris from getting into your eyes and to prevent frostbite on your hands. Understand the system you're working on, and adequately prepare by using the right tools for the job, and the recovery process will go much faster and more trouble-free than you think.

For Mechanical Contractors: Refrigerant Reclamation Q&A What is refrigerant reclamation? Refrigerant reclamation is the process of taking oil-laden, wet, contaminated refrigerant and processing it, to return it to virgin (ARI-700) standards. Refrigerant reclamation is accomplished by a combination of distillation, filtration, and drying. All contaminants such as moisture, oil, air, particulates, chlorides, and acid are removed. By law, the EPA certified reclaimer must test the refrigerant to verify that it meets or exceeds ARI 700 standards. Why use a refrigerant reclamation company? Why not just do it yourself? Before refrigerant can be reintroduced into a system with a different owner, it must be reclaimed to ARI-700 standard by an EPA-certified refrigerant reclamation company. Unless the used refrigerant is going back into the same system, or a system owned by the same company, it must be brought back to ARI 700 standards by an EPA-certified reclaimer. If you're not an EPA certified reclaimer, you can't reintroduce refrigerant into a different system. What does the reclamation procedure consist of? The refrigerant is distilled, filtered, dried, and finally tested to verify that it meets ARI standards. Once it's confirmed that it meets or exceeds ARI standards, it's packaged, or stored for packaging at a later date. It sounds simple, however, it's difficult to process 10,000 to 30,000 lbs. everyday, to handle 10 different refrigerant types simultaneously, to pass ARI standards every time, and to properly account for it to the customer and the EPA. How do the contractor and refrigerant reclaimer work together? Established reclaimers provide specialized services the mechanical contractor can't, or doesn't want to provide. Established reclaimers normally have an inventory of empty Department of Transportation (DOT) cylinders available for the mechanical contractor to use, or they can send their own technicians out to physically recover the used refrigerant as a subcontractor. If the used refrigerant isn't going to be returned to the existing system, the reclaimer will normally purchase the used gas, at a negotiated price. If the recovered gas is going to be returned to the same system, a few of the larger reclaimers can process the used refrigerants on-site to remove contaminants and greatly improve the performance of the system. What does the reclaimer do with the used refrigerant? After the refrigerant is weighed, processed, and tested to verify that it meets or exceeds ARI standards, it's packaged into new cylinders or drums for resale. How does one find a reclaimer? Visit www.epa.gov and search for refrigerant reclaimers. However, some refrigerant reclaimers have been around for many years and have learned how to do it right, and some have not. Some are well funded, and others are barely scraping by. The best advice is to ask around. Most of the larger reclaimers in the U.S., such as CFC Refimax, Smyrna, GA use some type of proprietary equipment. There are systems that only reclaim higher pressure refrigerants, and systems that deal with low pressure gases. More advanced systems, which are able to process both high and low pressure refrigerants, have been built in the last few years. Many reclamation companies can recover the refrigerant and reclaim the product. This enables the mechanical contractor to partner with the reclamation company along with their proprietary equipment, which allows the mechanical to utililize his technicians for mechanical repairs. There are a few reclamation companies whose equipment enables them to reclaim the refrigerant as well as recover it at the jobsite. This procedure is important if a system has contamination and needs flushing, or the refrigerant needs to be reclaimed and reintroduced into the system in a short period of time. What questions should I ask a reclaimer? 1. Ask for documentation for proper disposal of mixed refrigerants (you don't want to work with someone who is guilty of venting mixed refrigerants into the atmosphere in lieu of spending the money to have them properly disposed of). 2. Ask for test results verifying all refrigerants they use are processed to ARI 700 standards (independent testing by a certified lab is better than performing your own test). 3. Ask your peers and competitors who they use, and ask what their reclaimer is like to do business with. Know who you're working with; not all reclaimers adhere to the same rules. Sidebar authors: Ken Beringer is senior vice president, refrigerants, CFC Refimax, Smyrna, GA. Doug Romine is senior vice president, business development with Airgas, Inc. Airgas, an industrial gas company, purchased CFC Refimax as of January. 1.

Tim Wagaman is product manager for air conditioning tools and equipment for SPX Service Solutions, Owatonna, MN, which encompasses Promax, Robinair and Tif.