[TX2_ACTN] tx2 action
Function block TX2_ACTN directly controls ERC (energy recovery).
TX2_ACTN directly controls ERC (energy recovery). The positioning signal is calculated from weighted demand signals (from function block TX2_DMD), supply air setpoints, outside air status, and extract air status. The function block TX2_ACTN controls ERC so that the sum of the weighted demand signals for the air handling processes heating, cooling, humidification, and dehumidification is minimized.
Control strategy Economizer TX2
The Economizer TX2 control strategy comprises two focal points:
- The ERC control with regard to energy-optimized air handling processes.
- The control of air handling processing with regard to weighting (e.g. costs).
The function blocks TX2_DMD and TX2_ACTN are part of the Economizer TX2 control strategy and have the following functions:
- The function block TX2_DMD calculates energy-optimized air handling processes (based on enthalpy and aggregates used) and then calculates an energy-optimized demand for ERC. The energy-optimized demand signals additionally are multiplied by a weighting factor (e.g. with regard to costs), so that several weighted (e.g. costly) air handling processes have a superordinate demand for ERC. ERC then focuses on weighted (i.e. costly) air handling processes. Cheaper air handling processes thus are carried out mostly by other air handling processes.
- The function block TX2_ACTN controls ERC based on the demand signals weighted by function block TX2_DMD. Here, the function block TX2_ACTN determines the optimal operating point for ERC.
Process procedure in the function block
Step | Process procedure in the function block |
|---|---|
1 | The function block calculates the energy-optimized use of ERC as per the weighted demand signals. |
2 | The function block then issues the positioning signal for ERC. [Yctr] |
--- | The control response of TX2_ACTN can be set. [DmdFac] |
--- | The function can be enabled/disabled. |
Input | Description | Data type | Default value |
|---|---|---|---|
|
EnFnct | Enable function | Boolean | 1 |
0 - Off: [Yctr] = 0 | |||
SpTSu | Setpoint for supply air temperature
| Real | 22 [°C] 0.0...50.0 [°C] |
SpHuSu | Setpoint supply air humidity
| Real | 10.0 [g/kg] 0.0...20.0 [g/kg] |
PosMinOa | Minimum position for outside air damper
| Real | 30 [%] 0.0...100.0 [%] |
30: Recirculated air | |||
|
TOa | Outside temperature | Real | 20.0 [°C] -70.0...70.0 [°C] |
|
HuAbsOa | Outside air absolute humidty
| Real | 7.8 [g/kg] 0.0...20.0 [g/kg] |
|
TEx | Extract air temperature Room extract air temperature (see Engineering). | Real | 0.0 [°C] 0.0…50.0 [°C] |
|
HuAbsEx | Extract air absolute humidity Room extract air humidity (see Engineering) | Real | 7.8 [g/kg] 0.0...20.0 [g/kg] |
|
TEfcy | Temperature efficiency Temperature efficiency degree of used ERC. Typical values: | Real | 1.0 0.0...1.0 |
1: Recirculated air | |||
|
HuEfcy | Humidity efficiency Humidity efficiency degree of used ERC. Typical values: | Real | 1.0 0.0...1.0 |
1: Recirculated air | |||
WgHDmd | Weighted demand for heating Energy or cost-optimized demand signal for heating. Interconnected to function block TX2_DMD. Can be attenuated with [DmdFac]. | Real | 0.0 [K] 0.0...100.0 [K] |
WgCDmd | Weighted demand for cooling Energy or cost-optimized demand signal for cooling. Interconnected to function block TX2_DMD. Can be attenuated with [DmdFac]. | Real | 0.0 [K] 0.0...100.0 [K] |
WgHuDmd | Weighted demand for humidification Energy or cost-optimized demand signal for humidification. Interconnected to function block TX2_DMD. Can be attenuated with [DmdFac]. | Real | 0.0 [g/kg] 0.0...50.0 [g/kg] |
WgDhuDmd | Weighted demand for dehumidification Energy or cost-optimized demand signal for dehumidification. Interconnected to function block TX2_DMD. Can be attenuated with [DmdFac]. | Real | 0.0 [g/kg] 0.0...50.0 [g/kg] |
DmdFac | Demand factor The four weighted demand signals [Wg..Dmd] are attenuated to prevent oscillation of [Yctr]. | Real | 0.8 0.01...1.0 |
1: No attenuation | |||
Output | Description | Data type | Default value |
|---|---|---|---|
|
Yctr | Controller output | Real | 0.0 [%] 0.0…100.0 [%] |
0: No ERC required or [EnFnct] = Off. | |||
|
SysUnits | System of units Indicates the system of units used by the block. | Integer | 1: International system of units (SI) (fallback) 1...5 |
1: International system of units (SI) (fallback) | |||
ErrCode | Error code indication | Integer | 0: No error |
= 0 - No error | |||
Plant configuration
The Economizer tx2 control strategy is used for the following plant configurations:
- ERC, preheater, cooler, reheater, humidifier
- ERC, cooler, reheater, humidifier
(ERG = Mixing air dampers, rotational heat exchanger, plate heat exchanger, etc.)
The benefits of the Economizer tx2 strategy are used only if at least three air handling processes are present and ERC allows for humidity recovery. Recirculated air is best suited for humidity recovery.
Temperature sensor [TEx], [HuAbsEx]
If the temperature difference between extract air before ERC and the room air is big, an additional temperature sensor must be placed in the extract air before ERC.
The function blocks TX2_DMD and TX2_ACTN together form ERC control. These function blocks are linked with room and supply air control of an air conditioning system (min. 3 air handling processes) to form one control strategy (Economizer tx2).
Energy efficiency
The Economizer tx2 control strategy can be used as a supplement for other energy and cost optimization procedures:
- Peak demand optimization
- Ventilation time optimization: Scheduler program, Optimum Start Stop (OSSC).
- Setpoint field control (tolerance band for temperature and humidity)
- Night ventilation
- Return limitation for district heating
The function block processes the value at the inputs. The values are either default values of the function block or output values or output values of the pre-configured function blocks.