By Ralph Vergara
The basics of refrigerant recovery begin with having the proper equipment. You will need manifold gauges, safety glasses, gloves, a refrigerant recovery cylinder, scale, approved refrigerant recovery unit, and the proper hoses (including hoses with low-loss fittings) to connect to the discharge side of your recovery equipment.
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. Never recover refrigerant near an open flame, because it will decompose into phosgene gas. Breathing phosgene gas can be fatal.
When recovering refrigerant, always use a scale to prevent overfilling the recovery tank. Overfilling the recovery tank can cause it to rupture and severely damage equipment — a potentially fatal situation for service technicians and others in the area.
Some recovery equipment is available with an 80% overfill sensor or tank overfill sensor (TOS). A TOS is a cable that will interface with a liquidlevel switch on the recovery cylinder and shut off the power supply to the unit if the tank reaches 80% of its capacity. Working with highpressure refrigerants has unique safety issues. R-410A probably is the most commonly used high-pressure refrigerant today. Recovering it requires the use of different tanks, hoses, manifolds, and recovery equipment.
A standard 350 Department of Transportation (DOT) recovery cylinder will not work for high-pressure refrigerants. Instead, you must use a 400 DOT recovery cylinder. Unfortunately, there are no distinct markings indicating a 350 from a 400 DOT cylinder. Both are yellow on top and gray on the bottom. Always make sure to check the top of the cylinder to confirm that the cylinder is a 400 DOT.
The gauges used on a traditional manifold set do not read the level of pressures you will encounter with the high-pressure refrigerants. When working with high-pressure refrigerants, make sure you use a manifold set with a low-side gauge that reads pressures up to at least 500 psig, and a highside gauge that reads up to at least 800 psig. Make sure that you use hose assemblies that are rated by UL for high-pressure use.
When purchasing new recovery equipment look for recovery equipment that can be used on high-pressure refrigerants. They’re the wave of the future, and if you’re not working with them now, you will be in the near future.
Refrigerant Recovery Methods Always use a filter-dryer or particulate filter on your refrigerant recovery unit. It is also important to us an acid core dryer when recovering from a burned out system. Acid and particulate matter will cause damage to your refrigerant recovery system. If you use the appropriate filter on every job, your refrigerant recovery equipment should give you many years of trouble-free service.
The three different recovery methods are: vapor recovery, which is the most common; the pushpull method; and the liquid recovery method, which is gaining in popularity.
The following information describes the steps related to each recovery method. Remember, your system configuration may vary. Check your operation manual to find the proper configuration for your unit.
Vapor Recovery Method There are 10 steps for proper use of the vapor recovery method:
1. Connect a hose with a low-loss fitting on both ends to the discharge side of the recovery equipment.
2. Connect the other end of this hose to the tank liquid port on the recovery cylinder.
3. Place the recovery cylinder on a scale.
4. Connect a hose from the low-side service port of the HVAC system.
5. Connect the other end of this hose to the center (charging) port of your manifold set.
6. Connect a hose to the low-side of your manifold set.
7. Connect the other end of this hose to the suction side of the recovery equipment.
8. Connect a hose from the tank vapor port to the high gauge on the manifold set. This will allow you to monitor the tank pressure.
9. Close valves on manifold set.
10. Open vapor and liquid valves on the recovery cylinder.
11. Start the recovery system.
12. Allow unit to pull into the appropriate vacuum based on refrigerant type.
13. Close all valves and disconnect from the HVAC system, or begin purge cycle.
Liquid Recovery Method
Until recently, it was unheard of to recover direct liquid. But with the use of oil-less compressors and constant pressure regulator valves, it’s become the preferred method of recovery by most recovery equipment manufacturers.
Proper refrigerant disposal
In the natural course of your business, you’re bound to end up with refrigerant for which you have no need. Government regulations are very strict on what you can and can’t do with used refrigerant.
The guidelines are set up to avoid the damaging effects refrigerants can have on the atmosphere. According to amendments made to the EnvironmentalProtection Agency’s Clean Air Act in the 1990s, it is “against the law for any person, in the course of maintaining, servicing, repairing, or disposing of an appliance or industrial process refrigeration, to knowingly vent or otherwise release or dispose of any Class I or Class II substance used as a refrigerant in a manner which permits such substance to enter the environment.”
The term “appliance”refers to air conditioners, refrigerators, chillers, or freezers used for commercial or residential purposes. In general, if the refrigerant is not contaminated it can be recycled and reused. You can typically take the noncontaminated refrigerant back to the wholesaler for exchange. If the refrigerant is contaminated, you’ll need to send it to a reclamation facility. At the reclamation facility they’ll separate the refrigerant into the individual component refrigerants or incinerate it in accordance with EPA guidelines.
To locate the reclamation facility nearest you, visit this EPA Web site: http://www.epa.gov/Ozone/title6/608/reclamation/reclist.html.
Oil-less recovery equipment has an internal device to flash off the refrigerant. Oil-less compressors will tolerate liquid only if metered through a device like a CPR valve.
Don’t attempt to use the liquid recovery method unless your unit is designed to recover liquid.
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, such as refrigerant transfer, or if the system you’re servicing will allow you to recover liquid.
Push-pull Recovery method
Use the push-pull method only after you have first checked the configuration of the system being serviced. Here are the questions to ask first:
• Are less than 10 pounds of refrigerant in the system?
• Is the system a heat pump, or one with a reversing valve?
• Will the system allow a solid column of liquid to form?
• Does the system have an accumulator? If the answer to any of these questions is yes, refer to the vapor or liquid recovery methods.
Otherwise, here are 10 steps to using the push-pull recovery method:
1. Connect a hose from the tank vapor port to the center port of the manifold set.
2. Connect a hose from the low side of the manifold set to the suction side of the refrigerant recovery unit.
3. Connect a low-loss hose from the discharge side of the recovery unit to the low-side service port.
4. Connect the low-loss hose from the high-side service port to the tank liquid valve.
5. Place the tank on a scale.
6. Open valves on recovery cylinder.
7. Start refrigerant recovery machine.
8. Open the low-side valve on the manifold set.
9. Monitor the scale.
10. Switch the unit over to vapor recovery once the scale stops picking up weight.
Ralph A. Vergara is technical sales manager for Ritchie Engineering. Call him with questions at 800/769-8370 ext. 404, or e-mail him at firstname.lastname@example.org.
Additional recovery tips
1. Always use shortest hoses possible.
2. Using 3/8-in. hose will greatly increase your recovery rates.
3. Remove valve cores from system when possible.
4. Use a heat gun to get refrigerant to boil off.
5. Use liquid recovery when possible.
6. Additional information can be found at www.ul.com/refrigerationperformance.html, and www.ahri.org.
However, when comparing performance on the UL or AHRI websites, remember that vapor recovery is approximately 75 to 80% of the recovery process. It’s very important to use a recovery machine with a high vapor recovery rate. Liquid recovery is 20-25% of the recovery process. A refrigerant unit with the ability to recover liquid will speed up the first (liquid) part of the recovery process.