Occupied mode heating and cooling stages are controlled by the staged percent command. The stage percent command increases or decreases based on the relationship to operational space temperature and operational heating or cooling setpoint. The rate of change is determined by the deviation from the setpoint and length of time away from the setpoint
| No. Stages | PID percent command | |||||||
|---|---|---|---|---|---|---|---|---|
| 1st Stage | 2nd Stage | 3rd Stage | 4th Stage1 | |||||
| On | Off | On | Off | On | Off | On | Off | |
| 1 | 100% | 90% | ||||||
| 2 | 50% | 45% | 100% | 95% | ||||
| 3 | 33.3% | 30% | 66% | 63.2% | 100% | 96.7% | ||
| 4 | 25% | 22.5% | 50% | 47.5% | 75% | 72.5% | 100% | 97.5% |
Compressor operation
This section assumes free cooling is not available.
If the operating space temperature is 0.6°F or greater than the operating cooling setpoint, the staged percent command increases. Compressors turn on based on Table 1.
If the operating space temperature is 0.6°F or less than the operating cooling setpoint, the staged percent command decreases. Compressors turn off based on Table 1.
Compressors stage off in the reverse order that they turned on. For example, the first compressor to turn on is the last compressor to turn off.
Heating operation
If the operating space temperature is 0.6°F or lower than the operating heating setpoint, the staged percent command increases. Heating stages turn on based on Table 1.
If the operating space temperature is 0.6°F or greater than the operating heating setpoint, the staged percent command decreases. Heating stages turn off based on Table 1.
Heating stages turn off in reverse order, from the highest stage to the lowest stage.