The packaged air conditioners are used for the low to medium tonnage of air conditioning load ranging from 5 to 20 tons also higher. For smaller loads up to 5 tons single compressor is used. For the higher load of more than 5 tons two compressor are used in the package air conditioning system forming two independent refrigeration systems. Though the two systems are independent they are housed in the same supporting framework. The evaporator systems of these two systems are entwined together.
With the two compressors installed in the system there is facility for the capacity control of the air conditioning plant thus one can run the plant fully or partially as per the heating load or as per the number of rooms to be cooled. At full capacity both the compressors can be kept running, while at the partial load one of the compressors can be kept off. The capacity control can also be done automatically by thermostat. The two compressors also ensure that the air conditioning plant won't stop completely when one of the compressor breaks down, for the system can still keep on running though on partial capacity.
The water cooled condenser used with the two compressor system can be single shell but partitioned inside it for different passages for the refrigerant from the two compressors. There can also be two different water cooled condensers for two different systems. If the condenser is of air cooled type, there would be two condensers either placed side-by-side or entwined together just like the evaporator of the system.