EDC Building | Occupancy | Probabilistic Setback
Probabilistic setback
A comfortable indoor air temperature ensures occupant comfort. However, maintaining a comfortable indoor air temperature when the space is empty is unnecessary. Using a probabilistic prediction algorithm which forecasts days when occupancy in certain zones is unlikely, a temperature setpoint setback is automatically applied to these zones - the magnitude of the setback is determined by how unlikely occupancy is expected. Temperature setbacks are released (i.e., regular thermostat control is relinquished) if occupancy is detected in that zone. Adjusting the setpoint temperature in unoccupied zones can reduce heating and cooling energy use.
Temperature setpoints are automatically adjusted based on the number of consecutive day of the week (e.g., Monday, Tuesday) that a zone was not observed to be "likely occupied". A zone is considered "likely occupied" if the duration of detected occupancy exceeds 90 minutes. The table on the right lists the
applied setback/setup based on the number of consecutive day of the week.
For example, if a zone was not "likely occupied" for three previous Tuesdays, consecutively, a temperature setback/setup of 2°C shall be applied to that zone for the upcoming Tuesday.
Setbacks/Setups are relinquished (i.e, user-controlled setpoints are resumed) if occupancy is detected during the day.
| Number of consecutive day of the week | Setback/Setup |
|---|---|
| 0 | 0°C |
| 1 | 0.5°C |
| 2 | 1°C |
| 3 | 2°C |
| 4+ | 4°C |
The duration of detected occupancy is inferred by the number of times a zone's motion detector was triggered every 10 minutes in one day. For example, if a zone's motion detector was triggered 12 times in a single day, then it is inferred that the zone was occupied for 2 hours. This is
because there are 12 10-minute intervals within 2 hours (i.e., 12 times 10 minutes equals 120 minutes which equals 2 hours). Note that this is a very crude way of inferring occupant presence and duration - varying magnitudes of inaccuracies are expected.
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