One of the most common tasks that an HVAC technician will have to perform is refrigerant recovery. This has to be done when repairing or maintaining an HVAC system and you need to know what the best techniques are. There are 3 basic methods which can be used to recover refrigerants and they are liquid, vapor and push-pull.
When looking at refrigerant recovery techniques, liquid will be the fastest and the one that most technicians will use. This involves the transferring of the refrigerant while it is in its liquid state. However, it is important to note that this recovery option is not always possible, but should always be used if you can.
To start liquid recovery, you will first need to ensure that the system you are working on is completely turned off. You should also check that the recovery machine’s selector knob has been set to off and all of the valves on your manifold are closed. You should then connect the manifold to the system that you are going to service. The high-side will need to be on the liquid port and the low-side on the vapor port.
You will then have to place the utility hose from the manifold to the suction port of the recovery machine. The last step in the setup will be to connect the hose from the recovery cylinder’s liquid side to the discharge port. At this point, you will need to ensure that the hoses with the shut-offs are used on the suction and discharge ports as this is a legal requirement.
Before you start the actual recovery process, you will need to remove all of the non-condensable items from the hose. Now you can start the recovery process by turning the selector valve on the recovery machine to liquid. You will also need to open the high-side valve and the utility port.
The machine will continue to recover the liquid refrigerant until the low-pressure switch huts it down. The machine will then indicate that the recovery has been completed. At this point, you will need to shut the system off and turn the selector valve to off.
Another option when it comes to recovering refrigerant is to use vapor recovery. This is a slower method, but it is also the most commonly used method. As the name suggests, you will be recovering the refrigerant while it is a vapor state. The process for this method is very similar to that of the liquid recovery.
The primary difference is the state of the refrigerant. There are also different settings which need to be used on the recovery machine when using this method. Additionally, the recovery machine will condense the vapor into a liquid before it is transferred to the recovery cylinder.
As with the liquid recovery, you will need to ensure that the system has no power and that the recovery machine is off. All of the valves on your manifold will also need to be closed at this point. The connection of the manifold to the system you are working on will be the same as the liquid recovery.
You will then have to attach a 1/4 inch utility hose to the suction port of the recovery machine. A hose will also need to be attached to the liquid side of the recovery cylinder. This will need to connect to the discharge port. The same legal requirements need to be met when you are attaching the hose as with the liquid recovery.
When you are ready to start the recovery, you will need to turn the recovery machine on and set it to vapor. The utility port and low-side valve on the manifold will then need to be opened. The machine will start to recover the refrigerant and stop when the low-pressure switch is activated. The machine will tell you that it has completed the recovery and you can then turn it off.
You will then have to purge the system which is something that you should be doing after every recovery. To do this, you need to turn the machine on and set the selector valve to the purge setting. When the unit shuts down and the recovery complete lamp is lit, your vapor recovery will be over.
The last of the effective refrigerant recovery techniques is the push-pull method. This is actually a faster method than the liquid recovery, but consists of 2 steps. You will need to first recover the liquid and then change the hose connections to recover the vapor. This technique is generally only used when you have a large amount of refrigerant in the system.
When this technique is being used, the recovery machine will pull the vapor out of the recovery cylinder and will then create a high-pressure gas that pushes the liquid refrigerant out of the HVAC system. This technique should not be used if the system has less than 10 pounds of refrigerant or it has a heat pump. You will need a different setup for this technique and extra equipment to carry this out.
The extra equipment includes an extra hose, a sight glass rated for the pressure of the refrigerant you are working with and a recovery cylinder that has no more than 5 pounds of refrigerant. Once you have all this equipment, you can start. You will have to connect a hose to the discharge port of the recovery machine and the vapor side of the of HVAC systems type.
Another hose will need to be attached to the liquid side of the HVAC system and connect with the sight glass and the liquid side of the recovery tank. The last hose will need to be connected to the vapor side of the recovery tank and the suction port of the recovery machine. Once all of the hoses are in place, you need to purge them of non-condensable items.
You can then open the valves on the recovery tank and set the machine to vapor. While the recovery is in progress, you have to watch the sight glass. When passing liquid is no longer visible, the first step of the recovery is complete. You will then have to set up the recovery of the liquid.