From the largest walk-in freezer to the smallest water cooler, all refrigeration systems work with the same principles. A refrigerant absorbs heat inside of the cooling area and transfers that heat to the refrigerator's exterior. The refrigerant's heat absorption actually starts when the refrigerant boils in the refrigerator. When the refrigerant turns from a cool vapor to a warm liquid the heat transfer completes. Ideally the refrigerant will remain contained in the system. When a leak forms a technician must repair the leak, then charge the proper amount of refrigerant back into the refrigeration system. The technician must know how to charge a refrigeration system in question and in most cases, will have experience require to understand how to check superheat.
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Identify the Refrigerant
Before starting, learn if you can even do the work yourself as EPA requires certified personnel to change refrigerants and other chemicals for some refrigerated systems. If you are ok to charge the freon or other refrigerant, then start by check the refrigerator's identification tag to determine the type of refrigerant used in the system. The tag will state the refrigerant type and the amount of refrigerant, as measured in weight with which the manufacturer charged the system.
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Hook Up Refrigerant
Screw the middle hose fitting of a refrigeration manifold onto the valve of a jug of the correct refrigerant. A refrigeration manifold has three hoses, two gauges and two internal valves. The valve's handles, found on the manifold's sides, operate the two valves which regulate the refrigerant flow between the middle hose and the two outside hoses.
Open the refrigerant jug's valve two full turns. Turn the valve's handle clockwise by hand. New jugs of refrigerant may require starting the handle with pliers. Open each of the manifold's valve handles for one second. This will remove the air from each hose.
Screw the left manifold hose to the refrigerator's large service valve, found near the compressor on the large refrigeration line. If the service valve has a cap, then remove the cap with an adjustable wrench.
Screw the right manifold hose to the refrigerator's small service valve, found between the condensing coil and the evaporating coil on the small refrigerant line. Often the small refrigerant line will travel from the condensing coil to a spot near the large service valve. For convenience, the small service valve will connect to the small refrigeration line near the large service valve. If the small service valve has a cap, then remove the cap with an adjustable wrench.
How to Charge Freon
Weigh the refrigerant jug on a graduated weight scale to the nearest ounce. Turn the jug over. Keep the jug on the graduated scale. When the jug's valve faces downhill, liquid refrigerant will flow from the jug.
Turn the handle on the right-hand side of the manifold clockwise. This will open the manifold's valve. Keep the handle open until three quarters of the refrigerant's weighted charge has entered the system. Use the graduated scale to determine the correct charge.
Turn the handle on the left-hand side of the manifold clockwise. This will open the manifold's valve. Keep the handle open until the remaining one quarter of the refrigerant's weighted charge has entered the system. Use the graduated scale to determine the correct charge.
Close the refrigerant jug's handle and disconnect all hoses. Replace all service valve caps.