Data Aire dap4 User Manual page 85

Variable + Fixed Speed Compressors – Controlling Return Air Temp.
The variable compressor (C1) turns on when the return temperature rises above
the Setpoint + Deadband. As temperature continues to rise, the variable
compressor will run faster. Once it is running at 95% of maximum speed for the
"C2 On Delay" setting, the fixed speed compressor is allowed to run.
The Fixed speed compressor (C2) turns on when the return temperature rises
above the Setpoint + Deadband + The Stage-to-Stage setting.
The Fixed speed compressor (C2) turns off when the return temperature drops
below the Setpoint minus the Stage-to-Stage setting for the duration of the C2 Off
Delay time setting.
The variable speed compressor (C1) turns off when the return temperature drops
below the Setpoint minus The C1 Offset setting (default of 1.0°F).
Modulation of the variable compressor to control the return air temperature will be
by a proportional + Integral (PI) algorithm. The tuning parameters for this algorithm
are in the Factory Setting menu.
Note if the Energy Saver mode is running (Wtr Vlv configured as Engy Svg Cool or
Aux Chill Wtr in factory menu). The variable compressor turns on when the return
air temperature rises above the Setpoint + Deadband + Stage To Stage setting +
1.0°F. It turns off when the return air temperature drops below the Setpoint.
85