This article describes the differences between event scheduling and zone scheduling of HVAC, lighting, and security equipment in Events2HVAC (E2H).
Zone scheduling is a new feature that was added to E2H at v1.3.2. It provides more accurate occupancy control of a whole building or large zone than a fixed weekly building schedule set in a building automation system (BAS).
Event scheduling is the typical way E2H triggers commands to equipment. It uses event triggers to send commands to equipment assigned to a room (or rooms) based on room schedules pulled from a reservation system. The equipment can be an AHU, VAV box, door access terminal, etc. Event triggers can be executed on Event Start, Event Stop, Setup Start, or Teardown Stop.
When event triggers are used, the equipment is cycled on and off based on the consolidated schedule of all rooms mapped to the equipment.
Figure 1 - Event actions triggered off setup and teardown
In Figure 1 above, three rooms are served by an AHU. Events 1, 2, 4, and 5 overlap for the first occupied period. Event 3 occurs later in the day, so using event actions for the AHU, it is set to unoccupied for a period of time before it is returned to an occupied state prior to the start of Event 3. Note that the blue area of each event in the illustration represents a pre-start time set for the AHU in E2H; and the grey area represents setup and teardown periods set in the reservation system.
Event schedules for a zone are calculated at each event poll period.
Typical Use Cases for Event Actions
- Individual room or zone control based on room reservations: VAV boxes, dedicated AHUs, fan coil units (FCU), room access control, room lighting
- Larger AHUs that can be cycled throughout the day based on aggregate room schedules
Zone scheduling allows E2H to trigger actions based only on the first and last events scheduled each day for the zone. The feature is new and was added based on requests from customers.
- In one case, a customer wanted to open the building doors prior to the first scheduled event for the day, and lock them after the last event of the day. If you do this with event triggers as described above, the outside doors will lock and unlock throughout the day based on the events scheduled for the the building.
- In another case, a customer wanted to start a large AHU serving a building based on the first scheduled event in the morning, and shut it down after the last event scheduled for the day.
The addition of zone scheduling allows E2H to either eliminate fixed weekly schedules for a building or large zone, or alter fixed schedules to accommodate early events or after-hours events each day automatically.
Figure 2 - Zone actions triggered off setup and teardown
In Figure 2 above, three rooms are served by an AHU. There is a fixed weekly schedule for the AHU, from 8 am to 6 pm. Using zone actions for the AHU, the first event of the day triggers the AHU to start at around 1:30 am, and the last event of the day triggers the AHU to stop at 8 pm. As in the previous illustration, the blue area of each event represents a pre-start time set for the AHU in E2H; and the grey area represents setup and teardown periods set in the reservation system.
Zone schedules are calculated during each event poll period for the current and next day.
Typical Use Cases for Zone Actions
- Occupancy control of large air handlers (AHUs) that you don't want to cycle on and off - these may be older AHUs or AHUs that take too long to recover after they are shut off
- K-12 schools, office buildings and other facilities with fixed weekly base schedules (e.g. office hours, school hours, etc) that has scheduled events outside of these base schedules
- Outside door access control for a building or zone
- Outside parking or building lights