Occupancy

In the Pressure Control example application, occupancy is one of the factors determining the calculated heating temperature setpoint. In the application algorithm, the occupancy status has an impact on the control of a room temperature to achieve maximum energy efficiency taking into account the user’s comfort. The algorithm is designed to adjust the temperature setpoint to the occupancy status in order to maximize energy efficiency and minimize the effect on the user’s comfort—even the smallest range of the dead zone in the occupied mode generates savings for the system, while the effect on the user’s comfort is non-distinctive.

Primarily, the occupancy status is retrieved from the network. If there is no update from the network and the OccupancyMode Data Point falls into status different than OK, the local schedule is checked next and becomes a source for the occupancy status.

The occupancy status is also affected by the motion detector and window open/close state.

The motion detector, if available, is connected to the I1 digital input. Its state is read to the PresenceSensor variable. The PresenceSensorInvert variable has two modes, normal and invert, which are used to control the sensor state interpretation. In the normal mode, if the value from I1 is true, it means the sensor has detected presence and the occupancy status is switched to occupied. If I1 is false, it means no motion has been detected. If the sensor does not detect motion after the StandbyTimeOverride time expires, it switches the status to standby (temporarily unoccupied). In the invert mode, if I1 is true, it means no presence has been detected, and if I1 is false, it means that motion has been detected.

The window contact switch is connected to the I2 digital input. Its open/close state is read to the WindowContact variable. The WindowContantInvert variable has two modes, normal and invert, which are used to control the sensor state interpretation. In the normal mode, if the value from the I2 is true, the window is open, if the value is false, the window is closed. In the invert mode, if the I2 value is true, it means the window is closed, and if the I2 is false, the window is open. Most contact switches work in the invert mode. If there is no contact switch installed on the window, the WindowContantInvert works in its default, normal, mode.

Occupied Mode

In the occupied mode, the application algorithm works to reach a desired comfort temperature taking into occupied heating temperature setpoint (21°C/70°F) according to the following rule:

• if the temperature falls below the occupancy heating temperature setpoint (<21°C/70°F), the algorithm increases heating demand.

Standby Mode (Temporarily Unoccupied)

The standby mode means that the area is temporarily unoccupied (e.g., an employee has left the room for a meeting). It is normally used in combination with the presence sensor. In the standby mode, standby heating temperature setpoint is used (19°C/67°F). The occupied status changes to standby after the time set in the StandbyTimeOverride variable (by default, 15 minutes). If the presence sensor detect motion again, the status changes back to occupied. Occupancy in the standby mode does not change automatically to unoccupied, only the signal form the BMS can trigger the unoccupied status (in the OccupancyMode variable).

Bypass Mode (Temporarily Occupied)

The bypass mode means that the area is temporarily occupied (e.g., in a spare conference room, which is normally unoccupied, the bypass mode would be used for an occasional meeting), the occupied heating temperature setpoint is the same as in the occupied mode (21°C/70°F) but it is active for a specific time (by default, 2 hours) and switches back to a previous state.

Unoccupied Mode

The unoccupied mode triggers the unoccupied heating temperature setpoint (16°C/64°F). The unoccupied mode is usually activated from the BMS or the local schedule.