Buildings.Controls.OBC.ASHRAE.G36.ZoneGroups

Package of sequences in zone group level

Information

This package contains generic sequences in zone groups, according to ASHRAE G36 section 5.4.

Package Content

Name	Description
GroupStatus	Block that outputs the zone group status
OperationMode	Block that outputs the operation mode
ZoneGroupSystem	Compute the AHU operating mode from the group operating mode
ZoneStatus	Block that outputs zone temperature status
ZoneStatusDuplicator	Duplicate zone status output
Validation	Collection of validation models

Buildings.Controls.OBC.ASHRAE.G36.ZoneGroups.GroupStatus

Block that outputs the zone group status

Information

This sequence sums up the zone level status calculation to find the outputs that are needed to define the zone group operation mode.

It requires following inputs from zone lelvel calculation:

• zonOcc: if the zone-level local override switch indicates the zone is occupied,
• u1Occ: if the zone is occupied according to its occupancy schedule,
• tNexOcc: time to next occupied period,
• uCooTim: required cooldown time,
• uWarTim: required warm-up time,
• u1OccHeaHig: if the zone temperature is lower than the occupied heating setpoint,
• u1HigOccCoo: if the zone temperature is higher than the occupied cooling setpoint,
• u1UnoHeaHig: if the zone temperature is lower than the unoccupied heating setpoint,
• THeaSetOff: zone unoccupied heating setpoint,
• u1EndSetBac: if the zone could end the setback mode,
• u1HigUnoCoo: if the zone temperature is higher than its unoccupied cooling setpoint,
• TCooSetOff: zone unoccupied cooling setpoint,
• u1EndSetUp: if the zone could end the setup mode,
• TZon: zone temperature,
• uWin: True when the window is open, false when the window is close or the zone does not have window status sensor.

The sequence gives following outputs for zone group level calculation:

• uGroOcc: the zone group should be in occupied mode when there is any zone becoming occupied according its schedule or due to the local override,
• nexOcc: the shortest time to the next occupied period among all the zones in the group,
• yCooTim: longest cooldown time,
• yWarTim: longest warm-up time,
• yOccHeaHig: if there is zone with temperature being lower than the occupied heating setpoint, so the group could be in the warm-up mode,
• yHigOccCoo: if there is zone with temperature being higher than the occupied cooling setpoint, so the group could be in the cooldown mode,
• yColZon: total number of zones that the temperature is lower than the unoccupied heating setpoint,
• ySetBac: check if the group could be into setback mode due to that the average zone temperature is lower than the average unoccupied heating setpoint,
• yEndSetBac: check if the group should end setback mode due to that all the zone temperature are above their unoccupied heating setpoint by a limited value,
• yHotZon: total number of zones that the temperature is higher than the unoccupied cooling setpoint,
• ySetUp: check if the group could be into setup mode due to that the average zone temperature is higher than the average unoccupied cooling setpoint,
• yEndSetUp: check if the group should end setup mode due to that all the zone temperature are below their unoccupied cooling setpoint by a limited value,
• TZonMax: maximum zone temperature in the zone group,
• TZonMin: minimum zone temperature in the zone group,
• yOpeWin: total number of opening windows.

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.ASHRAE.G36.ZoneGroups.OperationMode

Block that outputs the operation mode

Information

This block outputs VAV system operating mode. It is implemented according to ASHRAE guideline G36, section 5.4.3, section 5.4.4, section 5.4.5 and section 5.4.6.

Note that, from the user's point of view, schedules can be a set for individual zones, or they can be set for an entire zone group, depending on how the user interface is implemented. From the point of view of the BAS, individual zone schedules are superimposed to create a zone-group schedule, which then drives system behavior.

1. All zones in each zone group shall be in the same zone-group operating mode. If one zone in a zone group is placed in any zone-group operating mode other than unoccupied mode (due to override, sequence logic, or scheduled occupancy), all zones in that group shall enter that mode.
2. A zone group may be in only one mode at a given time.

Each zone group shall have the operating modes shown below.

Occupied Mode

A zone group is in the occupied mode when occupancy input u1Occ is true. This input shall be retrieved from other sequences that specifies occupancy variation and time remaining to the next occupied period tNexOcc. A zone group could be in the occupied mode when any of the following is true:

• The time of day is between the zone group's scheduled occupied start and stop times.
• The schedules have been overriden by the occupant override system.
• Any zone local override timer is nonzero.

Warm-up Mode

Warm-up mode shall start based on the zone with the longest calculated warm-up time maxWarUpTim requirement, but no earlier than 3 hours (preWarCooTim) before the start of the scheduled occupied period, and shall end at the scheduled occupied start time. Zones where the window switch indicates that a window is open shall be ignored. Note that for each zone, the optimal warm-up time shall be obtained from an Optimal Start sequences, computed in a separate block. The figure below shows the sequence.

Cooldown Mode

Cooldown mode shall start based on the zone with the longest calculated cooldown time maxCooDowTim requirement, but no earlier than 3 hours (preWarCooTim) before the start of the scheduled occupied period, and shall end at the scheduled occupied start time. Zones where the window switch indicates that a window is open shall be ignored. Note that for each zone, the optimal cooldown time shall be obtained from an Optimal Start sequences, computed in a separate block.

Setback Mode

During unoccupied mode, if any 5 zones (or all zones, if fewer than 5) in the zone group fall below their unoccupied heating setpoints, or if the average zone temperature of the zone group falls below the average unoccupied heating setpoint (uSetBac becomes true), the zone group shall enter setback mode until all spaces in the zone group are 1 °C (2 °F) above their unoccupied setpoints (uEndSetBac becomes true).

Freeze Protection Setback Mode

During unoccupied Mode, if any single zone falls below 4 °C (40 °F), the zone group shall enter setback mode until all zones are above 7 °C (45 °F), and a Level 3 alarm shall be set.

Setup Mode

During unoccupied mode, if any 5 zones (or all zones, if fewer than 5) in the zone group rise above their unoccupied cooling setpoints, or if the average zone temperature of the zone group rises above the average unoccupied cooling setpoint (uSetUp becomes true), the zone group shall enter setup mode until all spaces in the zone group are 1 °C (2 °F) below their unoccupied setpoints. Zones where the window switch indicates that a window is open shall be ignored.

Unoccupied Mode

Unoccupied mode shall be active if the zone group is not in any other mode.

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.ASHRAE.G36.ZoneGroups.ZoneGroupSystem

Compute the AHU operating mode from the group operating mode

Information

This sequence specifies the operation mode of a AHU system, which may serve multiple zone group. It is implemented according to Section 5.15.1 of ASHRAE Guideline G36, May 2020.

When zone group served by an air-handling system are in different modes, the following hierarchy applies (highest one sets AHU mode):

1. Occupied mode
2. Cooldown mode
3. Setup mode
4. Warm-up mode
5. Setback mode
6. Freeze protection setback mode
7. Unoccupied mode

See the operation mode enumeration in Buildings.Controls.OBC.ASHRAE.G36.Types.OperationModes for the detailed description.

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.ASHRAE.G36.ZoneGroups.ZoneStatus

Block that outputs zone temperature status

Information

This block outputs single zone status. It includes outputs as following:

• the times for cooling-down (yCooTim) and warm-up (yWarTim) the zone,
• THeaSetOn: the zone occupied heating setpoint,
• yOccHeaHig: if the zone temperature is lower than the occupied heating setpoint,
• TCooSetOn: the zone occupied cooling setpoint,
• yHigOccCoo: if the zone temperature is higher than the occupied cooling setpoint,
• THeaSetOff: the zone unoccupied heating setpoint,
• yUnoHeaHig: if the zone temperature is lower than the unoccupied heating setpoint,
• yEndSetBac: if the zone temperature is higher than the unoccupied heating setpoint with the given limit bouLim, then the zone should be out of the setback mode,
• TCooSetOff: the zone unoccupied cooling setpoint,
• yHigUnoCoo: if the zone temperature is higher than the unoccupied cooling setpoint,
• yEndSetUp: if the zone temperature is lower than the unoccupied cooling setpoint with the given limit bouLim, then the zone should be out of the setup mode.

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.ASHRAE.G36.ZoneGroups.ZoneStatusDuplicator

Duplicate zone status output

Information

This block duplicates the signals of nZon by converting the input vector-valued signals of dimension nZon to a matrix-valued output of dimension [nZonGro, nZon].

This block prevent the use of for loops in the connectors between zones and zone groups by connecting all the zones to each Buildings.Controls.OBC.ASHRAE.G36.ZoneGroups.GroupStatus.

Parameters

Connectors

Modelica definition