The need to increase refrigerant pressure is an indication of failure; refrigerant is not a consumable item. A properly functioning air-conditioning system does not require periodic recharging, but all systems are subject to failure. This includes window air conditioners.
Newly installed systems need to be charged, as do air conditioners with a newly replaced component. The most common cause of low pressure or no pressure is leakage from somewhere in the system. Because pressure equalizes, the refrigerant will escape from the system until it is at the same pressure as the atmosphere. The only cause for an unacceptably high pressure is installer error; refrigerant does not increase to an unacceptable pressure during any normal function.
Increasing refrigerant pressure in an air-conditioning system is a skilled task. If you are unfamiliar with the process and the chemicals, it should be left to a skilled operator. If you are comfortable undertaking the project yourself, use the refrigerant canister, the manifold hoses and the pressure gauges strictly according to the manufacturer’s instructions. Consult the air conditioner’s data plate or the manufacturer’s instruction booklet to learn the correct refrigerant, and use only that type. Ensure that the compressor is not functioning while the pressure is increased. After service, ensure that the valves are firmly closed.
An overcharged system can radically shorten compressor life, but simply releasing some of the surplus charge is not an option. It is imperative that the excess refrigerant not enter the atmosphere; it must be vented into a recovery cylinder. The intentional venting of refrigerant into the atmosphere has been illegal since July 1, 1992. Section 608, Part 82, Subpart F of the Clean Air Act mandates the recovery and recycling of both hydro-chlorofluorocarbons, or HCFCs, and chlorofluorocarbons, or CFCs. Both chemicals deplete the ozone layer if released, and both are present in the refrigerants most commonly used in air conditioners.