As a service technician, the most common task you will have to complete is refrigerant recovery. There are a few techniques that you can use to do this, but there are some which are considered more effective than others. The 2 techniques that you need to know about are liquid recovery and push-pull recovery.
The Liquid Recovery Technique
The liquid recovery technique is actually the most commonly used because it is the fastest. As the name suggests, you will be moving the refrigerant when it is in a liquid state. However, it is important to note that while this is the fastest technique, it cannot be used at all times. There are certain HVAC systems which do not allow for the liquid recovery of refrigerants for cooling and the vapor method will need to be used.
To start the liquid recovery technique, you will need to ensure that the system with the refrigerant has been turned off. You should never complete this recovery when the device is still on as this will be dangerous and will cause damage to both your recovery machine and the system you are working on.
Once you have ensured that the system is off, you will need to ensure that your recovery machine has been set to off and that all of the valves have been closed. You should then connect the manifold of the machine to the system you are going to be servicing.
After doing this, you will need to connect the utility hose to the suction port of the recovery machine. This hose will need to connect to the manifold. You will also need to connect a hose to the discharge port of the system and link that to the recovery cylinder. You need to ensure that this is done on the liquid side or the recovery will not work correctly.
At this point, you have to purge the hoses of any condensing particles. This can cause issues with the recovered refrigerant that you will want to avoid. You can now open the valve on the recovery tank and turn your machine on. The selector valve will need to be placed on the liquid setting.
Your recovery machine will then start the liquid recovery process. This will continue until the low-pressure switch shuts the unit down. A light should be turned on at this point which tells you that the recovery has been completed.
The Push-Pull Technique
The other effective recovery technique that you need to know about is the push-pull technique. This is slightly longer and will have 2 parts to it. Additionally, this technique should only be used when you are dealing with a system that has more than 10 pounds of refrigerant in it. If the system has less, you should look at the liquid recovery system as it would be more effective.
When you use this technique, you will be pulling the vapor from the recovery container and push the liquid refrigerant out of the system. While this technique should not be used with systems that have less than 10 pounds of refrigerant, you should also not use it when the system is a heat pump or if it does not allow for the removal of liquid refrigerant. It is also important to note that you are going to need additional equipment when using this technique. You are going to need an extra hose, a recovery cylinder with less than 5 pounds of refrigerant as well as a sight glass.
To start the process, you need to attach a hose to the discharge port of the recovery machine. This should be connected to the vapor side of the system with the refrigerant that you want to recover. Another hose will have to be connected to the liquid side and you need to attach this to the sight glass. This connection should then be attached to the liquid side of your recovery machine.
The last step will be to connect a line from the vapor side of the recovery container to the suction port of the recovery machine. When all of the connections are in place and secure, you can start to purge the hose. All of the valves on the recovery container will then have to be opened.
On your recovery machine, you will need to place the selector valve on vapor. The unit can then be turned on and the recovery operation will start. While this process is going on, you will need to keep watching the sight glass. When you can no longer see the passing liquid in the sight glass, the first stage of the recovery technique will be complete.
At this point, you will need to close the vapor valve and let the unit run until you are told that the recovery is complete. When this happens, you will need to turn off the system and turn the selector valve to the off setting. You then have to purge the lines of the machines to prevent any loss of refrigerant.
You will now have to complete the second part of the technique which uses a setup that is identical to the vapor recovery technique. Once you have reconfigured the hoses on the system, you will be able to turn the selector valve to vapor. This will start the vapor recovery process and it will continue until the unit automatically shuts off. You will then have to purge the system on last time.
It is important that you do not forget about the final purge of the system in this recovery technique. This is due to the fact that the last purge will clear the unit of refrigerant and reduce the risks of any cross contamination. The lifespan of your equipment will also be prolonged when you do this.
There are a few refrigerant recovery techniques that you can use, but some are more effective than others. The fastest will be the liquid recovery technique which is very similar to the vapor recovery technique. The push-pull technique is ideal for larger systems, but is a 2-part process.