While modulating HGR is active, the staging of compressors is controlled by comparing Evaporator Coil Tempand OprEvapTempSp. If Evaporator Coil Temp > OprEvapTempSp, then StgClgCmd increases and compressors turn on. If Evaporator Coil Temp < OprEvapTempSp, then StgClgCmd decreases and compressors turn off.
Traditional thermostat calls (Y1, Y2, etc.) will not directly cause compressors to stage on/off. However, they are used to determine if there is a demand for cooling.