When free cooling is available and the operating space temperature is greater than the operating cooling setpoint, the dampers modulate to control the upper SAT setpoint +/- 0.5°F.
If the economizer output is at 100% for 5 consecutive minutes and the operating space temperature is 0.6°F or greater than the operating cooling setpoint, the staged percent command starts to increase and energizes compressors. See Table 1 for additional information.
As soon as the staged percent command begins to increase, the economizer remains at 100%. If the operating space temperature drops to less than 0.6°F above the operating cooling setpoint, the staged percent command holds the current value.
If the operating space temperature drops 0.6°F or more below the operating cooling setpoint, the staged percent command begins to decrease.
If the staged percent command remains at 0 for 5 consecutive minutes the economizer modulates to control to the upper SAT setpoint +/-0.5°F.