The following list includes all data points that can be read and written from a BACnet primary plant. The items ensure coordination between primary plant and the room. In addition, appropriate Desigo primary application for the given room function is mentioned.
Data point name | Description | Desigo primary application |
|---|---|---|
HReq | The central function prepares one hot water demand acquisition and evaluation to the connected rooms for the primary plant. The enumerated result can include: 1:Off | PXC {HGrp65} |
SpHReq | Setpoint for heating request | PXC {HGrp65} |
HwTOa | BACnet reference for primary plant: Outside temperature of the hot water supply chain | Data point outside temperature of hot water supply chain |
Setpoint for heating request.
Setpoint for heating request influenced by:
- Base setpoint for heating
- Valve position(s) of heating valve in the group
Heating curve based on outside air
Each DXR2 room automation station calculates heating and cooling demand and makes the results available via a group of the central function to the hot water supply chain.
The hot water demand setpoint is calculated in the central function using a heating curve based on the outside temperature.
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Sp | Setpoint |
| |
TOa | Outside temperature |
| |
SpTFlDs | Flow temperature setpoint for design outside temperature | 70 [°C] | |
TOaDsgn | Design outside temperature | -11 [°C] | |
SpTFlHi | Flow temperature setpoint for high outside temperature | 25 [°C] | |
TOaHi | Outside temperature high | 15 [°C] | |
Figure: Characteristic curve for the outside temperature-dependent heating curve
The heating request setpoint is influenced by the evaluation of valve positions.
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HwVlvPosEvl | Supply chain hot water valve position evaluation ▶Average of the largest valve position | |
HwSpCorrTFlHi | Supply chain hot water setpoint correction for higher flow temperature | |
HwSpCorrTFlLo | Supply chain hot water setpoint correction for lower flow temperature | |
Figure: Setpoint heating request
Hot water
Deactivate sequences
The central function can disable the hot water equipment in the rooms based on outside temperature. The heating sequences in the group are locked as soon as the configured value for the outside temperature is reached.
Description | Name | Default value |
|---|---|---|
Heating limit | HLm | 16 [°C] |
Time constant for heating limit | TiConHLm | 2 [h] |
Hysteresis for heating limit | HysHLm | 1 [K] |
Valve protection
Valve actuators are operated from time to time to prevent them from seizing after long periods of inactivity (e.g. heating valve during the summer). The valve actuator is controlled to lose as little heating energy as possible.
The central function for the hot water supply chain performs the valve protection function and can be changed in the parameters as needed.
Description | Name | Default value |
|---|---|---|
Kick value | KickVal | 50 [%] |
Kick time | TiKick | 2 [Min] |
Kick cycle | KickCyc | 500 [h] |
Centrally override valves
Central functions permit the central override of all valves in the supply group. The following parameters can be used.
Description | Name | Default value |
|---|---|---|
Enable valve position overridden value 0:No | EnVlvPosOvrr | 0:No |
Enable valve position overridden value | VlvPosOvrr | 100 [%] |