are of different sizes thus as shown by just having the economized operation on or off for each of the two compressors in addition to the conventional modes of operation eight levels of capacity can be provided in the chart illustrated as fig2 the compressor associated with circuit 2 is larger such that these eight numerically different stages of unloading are provided a control 40 is thus operable to either turn off the compressors 22 a and 22 b or run the cycle with the economizer expansion device 30 shut down to stop economized operation it should be understood that the economizer expansion device 30 may also be a shut off device or a separate shut off device could be utilized in combination with the expansion device the separate shut off device can be upstream or downstream of the economizer heat exchanger 32 further it should be appreciated that while the flow from the tap 28 and the main flow 26 are both shown to pass in the same direction through the economizer heat exchanger 32 in preferred embodiments they preferably flow in a counter flow relationship also it has to be understood that additional stages of unloading can be provided by the conventional unloaded and unloaded economized operation modes the control can compare the required load and system capacity and match the demand more accurately than the prior art as shown for example in fig3 without the economized operation the actual capacity provided does not come nearly as close to the demand and also cannot meet the higher levels of demand that can be met by the disclosed two economizer circuit system the nominal capacity of circuit a is less than circuit b as can be appreciated from.