EPA Type 2 Chapter 3
Refrigerant Recovery
In this module, we will discuss the different refrigerant recovery methods and a couple of techniques for faster recovery. Skip to quiz!
Recovery Procedure
Recall that refrigerant recovery is when a technician removes refrigerant from a system and stores it in an external container. It is necessary to recover and remove the entire or maximum possible amount of refrigerant.
The refrigerant can be recovered in liquid form or vapor form. It is necessary to recover both liquids as well as vapor refrigerant from the system for complete recovery. Let us discuss this a bit more.
While recovering, liquid refrigerant is recovered from the liquid line in the system.
Refrigerant is first recovered in liquid form for faster recovery.
As refrigerant oil is mixed with refrigerant, liquid recovery causes loss of refrigerant oil.
After liquid recovery, the remaining refrigerant is recovered in vapor form. Vapor recovery is slow & consumes more time. So to save time, the recovery process is started by removing the liquid part first.
While recovering, vapor refrigerant is retrieved from the vapor line in the system.
A lower amount of refrigerant oil is mixed with the vapor as compared to liquid refrigerant.
So vapor recovery minimizes the loss of refrigerant oil from the system during recovery.
Recall that atmospheric pressure is the pressure of the surroundings. Sometimes, leaks in the appliance cause air to leak inside during recovery, and a complete recovery cannot be made. In such cases, recovery from the appliance is only possible till atmospheric pressure.
Recovery Time
Recovery time is the time it takes to recover a refrigerant. Generally, we want to recover refrigerants in the least possible amount of time.
Recall the factors affecting the time it takes to recover refrigerant:
Ambient Temperature, and
Hose Length
We will learn about two more techniques to speed up recovery:
Liquid Recovery
Recovery Tank Temperature
As already discussed, liquid recovery is faster and reduces the recovery time. Recall that the pressure inside the liquid side is higher. The higher pressure pushes the liquid out of the system into the recovery tank more quickly.
Recall that the pressure and temperature of any substance are directly related to each other. Cooling the tank reduces the temperature and pressure inside it.
Low pressure inside the recovery tank,
Creates more space inside the tank and
Reduces the resistance to refrigerant flow.
This leads to a quicker recovery.
In this module, we discussed the different refrigerant recovery methods. We also learned a couple of techniques for faster recovery.
Recovery Equipment
In this module, we will discuss the pieces of equipment used for the recovery process. We will also discuss a few processes to be done before starting refrigerant recovery. Skip to quiz!
Recovery Equipment
The main pieces of equipment necessary to perform refrigerant recovery from any system are:
Recovery Machine
Recovery Tank
Digital weighing scale
Low-loss fittings and gauges
A recovery machine contains a compressor to suck out the refrigerant during recovery. There are a few different types of recovery units; two of which we will be discussing here:
Hermetic Recovery Units
Water-Cooled Recovery Unit
Recall that a hermetic compressor has all the components in a single shell. A hermetic recovery machine uses a hermetic compressor — the compressor motor, when working, produces a lot of heat.
A deep vacuum in a system is very close to zero pressure. Drawing a deep vacuum means that minimal refrigerant is left in the system, which needs to be sucked out.
Hermetic recovery machines depend on the flow of recovered refrigerant to cool it down. When drawing a deep vacuum, the compressor motor overheats as there is little refrigerant flow to cool it down. This overheating is a drawback of hermetic units.
A water-cooled recovery unit uses a condenser coil that cools down the recovered vapor refrigerant and converts it into a liquid. The recovery unit’s condenser coil is similar to the condenser coil in a refrigeration appliance.
Local municipal water supply is continuously passed over the condenser coils to cool it. A water-cooled recovery unit is generally used to recover large amounts of refrigerant.
Recall that recovery hoses and gauges are connected to the appliance for purposes like recovery, evacuation, and troubleshooting. All pieces of equipment used for any such purposes and manufactured after November 15, 1993, must be equipped with low-loss fittings.
Low-loss fittings minimize the loss and venting of refrigerant fluid while connecting and disconnecting the hoses to the appliances’ service valves. Self-sealing connectors and hand valves are few types of low-loss fittings.
Self-sealing connectors only require screwing or unscrewing of the cap and no force to connect them to the appliances’ service valves. Similarly, hand valves only require the technician to turn a valve.
Note that it is not necessary to report the purchase of any recycling and recovery equipment to the EPA.
Processes Before Recovery
Before starting with the recovery process, a few steps are related to the recovery equipment that should be followed.
Before transferring the refrigerant into an empty refrigerant cylinder, it is necessary to evacuate the cylinder first. It is because of the possibility that the empty cylinder might have outside air filled in it. Recall that air is non-condensable, and we want to avoid mixing air with the refrigerant.
All recovery machines have a filter at their inlet used to filter out the solid contaminants present in the refrigerant if any. After recovery, the filter has traces of the refrigerant trapped inside it.
Recall that mixing of two refrigerants is prohibited. Before starting recovery for a new appliance, the recovery machines’ filter should be changed. It is to avoid mixing of the two refrigerants.
In this module, we discussed the pieces of equipment used for the recovery process. We also learned about a few processes to be done before starting refrigerant recovery.
Recovery Precautions
In this module, we will discuss the different precautions to be taken during a recovery process. We will also go about some techniques to be followed during recovery. Skip to quiz!
Recovery Process Precautions
Recall that venting refrigerants into the atmosphere is prohibited. Before starting recovery, a few precautionary steps are necessary to prevent venting.
A technician should always check the service valve positions before starting recovery. This is to re-ensure that no valve is left open by mistake.
The refrigerant recovery machines also use oil for lubrication. This oil level must also be checked before starting the recovery process. Low oil levels might damage the recovery machine due to insufficient lubrication and cause venting.
A parallel compressor system has multiple compressors used in a single appliance. The compressors are connected in parallel so that all the compressors have a single outlet supply to one single outlet line.
It is also famously known as a parallel rack system. Such systems are commonly found in supermarket refrigeration and multiplexes.
Because the outlet is common, the pressure in the outlet line will be equal to the pressure developed by one single compressor. As all the compressors supply to a single outlet line, it is called an open equalization connection.
To recover the refrigerant from these systems, it is necessary to isolate these parallel compressors. This is because even if a single compressor is not isolated it can again start the refrigeration cycle in the system via another compressors’ pressure.
Recall that recovered refrigerant may contain impurities like
Refrigerant oil
Moisture
Acids and
Solid particle impurities
We will discuss a bit about refrigerant oil being an impurity.
Recall that refrigerant oil is mixed with the refrigerant. The refrigerant oil mixed with refrigerant cannot be filtered out and reused. So the oil recovered along with refrigerant is nothing but impurity removed.
System Dependent Recovery requires the pressure of a functioning compressor to recover refrigerant. This is also called passive recovery.
If we connect a non-pressurized refrigerant container to the system, the pressure of the container is lower than the pressure inside the system. The refrigerant will naturally flow from high to low, helping us recover our refrigerant. This is how system-dependent recovery works.
System dependent recovery is limited to appliances with 15 pounds or less of refrigerant. Using this method for appliances having more than 15 pounds is not feasible and is prohibited.
Specific Recovery Techniques
Recall that the receiver tank is a storage vessel for the refrigerant liquid coming out of the condenser coils in an appliance. The receiver tank also plays a major role during refrigerant recovery and servicing an appliance.
For an appliance with a receiver tank, the refrigerant is generally recovered from the receiver tank outlet. Note that this can only be done if the receiver tank outlet is at a lower height than the condenser coil outlet. If the receiver tank outlet is higher than the condenser outlet, the refrigerant is removed from the condenser outlet.
Recall that a liquid cannot rise from a lower position to a higher position by itself. Refrigerant should always be recovered from the lower outlet. This will minimize the risk of venting due to the refrigerant liquid being stuck in the system.
While servicing a unit having a receiver tank, a different technique can be used. Instead of recovering in a refrigerant tank, a technician can pump down the refrigerant into the receiver tank and isolate it.
The receiver tank acts as a refrigerant cylinder and stores the refrigerant in it while servicing the appliance. This saves time and effort.
In this module, we learned about the different precautions to be taken and some techniques to be followed during a recovery process. These techniques and precautions are fundamental to prevent venting, protect your equipment and the appliance from any damage.
Question #1: Recovering refrigerant from a system in the liquid phase will cause the loss of which of the following?
Water
Oil
Refrigerant
Non-condensables
Scroll down for the answer...
Answer: Oil
Refrigerant oil is mixed with liquid refrigerant in high quantities. During liquid recovery, the oil is recovered along with the refrigerant. This refrigerant oil is lost and can’t be filtered back.
Question #2: After the refrigerant liquid has been recovered from the appliance, any remaining vapor is;
purged to the atmosphere.
isolated in the appliance.
pumped into an appliance receiver.
removed by the recovery system.
Scroll down for the answer...
Answer: removed by the recovery system
After liquid recovery, vapor refrigerant in the system should also be recovered using the recovery equipment.
Question #3: A technique to speed up the recovery process is;
Use a plastic recovery tank.
Cool the recovery cylinder.
Use a four-stage vacuum pump.
Heat the recovery cylinder.
Scroll down for the answer...
Answer: Cool the recovery cylinder
Cooling the recovery cylinder reduces the pressure inside it. This creates more space inside the tank and reduces the resistance to refrigerant flow, leading to a quicker recovery.
Question #4: A hermetic recovery machine when drawing deep vacuums will;
Run faster than other recovery units
Overheat due to reduced flow of refrigerant through the compressor.
Cause high compression of recovered refrigerant.
Make the oil used in the hermetic compressor become highly viscous.
Scroll down for the answer...
Answer: Overheat due to reduced flow of refrigerant through the compressor
When drawing a deep vacuum, the hermetic compressors’ motor overheats as there is little refrigerant flowing through it to cool it down.
Question #5: During refrigerant recovery, local municipal water supply is used to cool the;
Water-cooled chillers.
Hermetic recovery unit.
Water-cooled recovery unit.
Deionized water recovery unit.
Scroll down for the answer...
Answer: Water-cooled recovery unit
Local municipal water is continuously passed over the condenser coils of a water-cooled recovery unit during recovery.
Question #6: Self-sealing connectors and hand valves are used because they;
Minimize the chance of an explosion.
Minimize refrigerant mixing with the refrigerant oil.
Minimize refrigerant release when hoses are connected and disconnected.
Prevent vapor lock during liquid transfer.
Scroll down for the answer...
Answer: Minimize refrigerant release when hoses are connected and disconnected
Self-sealing connectors and hand valves are a type of low-loss fittings.
Low-loss fittings minimize the loss and venting of refrigerant fluid while connecting and disconnecting the hoses.
Question #7: What should be done before transferring refrigerant to an empty cylinder?
The refrigerant should be chilled.
The refrigerant should be mixed.
The cylinder should be heated.
The cylinder should be evacuated.
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Answer: The cylinder should be evacuated
Before transferring refrigerant into an empty cylinder, it should first be evacuated to remove the non-condensable gases from the refrigerant tank.
Question #8: What steps should be taken before using a recovery unit to remove a charge?
Acid testing the refrigerant.
Purging the recovery unit with nitrogen.
Changing the oil in the recovery unit.
Checking the service valve positions and recovery oil level, when applicable.
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Answer: Checking the service valve positions and recovery oil level, when applicable.
While using a recovery unit, a technician should first check the service valve's positions to prevent refrigerants' venting.
The oil level in the recovery unit must also be checked before starting the recovery process.
However, to detect a refrigerant leak, electronic refrigerant detectors also known as room sensors are used.
Question #9: Refrigerant cannot be recovered without isolating a parallel compressor system because of;
the service valve connection.
the electrical connections.
an open equalization connection.
the thermal bleed connection.
Scroll down for the answer...
Answer: an open equalization connection.
A parallel compressor system has an open equalization connection.
So it would be impossible to recover refrigerant without isolating the parallel compressor system.
Question #10: When should refrigerant be removed from the condenser outlet?
When the condenser is below the receiver.
When the condenser is on the roof.
When the condenser is inoperative.
When the condenser is above the receiver.
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Answer: When the condenser is below the receiver.
If the condenser outlet is lower than the receiver tank outlet, the refrigerant is removed from the condenser outlet.
If this is not done, the refrigerant liquid will be stuck in the condenser coils
Question #11: When servicing an appliance having a receiver/storage tank;
the compressor discharge valve should be closed.
the compressor suction valve should be closed.
refrigerant should be pumped down to and isolated in the receiver.
a gauge pressure of “0” psig should be achieved by venting.
Scroll down for the answer...
Answer: refrigerant should be pumped down to and isolated in the receiver.
Multiple pressure relief valves should never be installed in series to the system lines.
When servicing an appliance having a receiver tank, the refrigerant should be pumped down to and isolated in the receiver tank.
This saves the time and effort of the technician.