EPA 608 Type 2 Chapter 9 (Take full course for free)
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!
1. 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.
2. 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.
3. Conclusion
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: 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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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 #2: 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.
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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 #3: 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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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 #4: 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” psia should be achieved by venting.
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refrigerant should be pumped down to and isolated in the receiver.
Multiple pressure relief valve 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.