[CGenCtl22] Sensors, setpoints and control for multiple refrigeration generators
Program block, name / node subtype: [CGenCtl22] Sensors, setpoints and control for multiple refrigeration generators
Library hierarchy: Cooling and refrigeration equipment
Family: CGenCtl
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Configurator
Program blocks are stored in the library without I/Os. Use the auto-create and auto-connect functions to create I/Os and/or to connect them to the interface blocks, e.g., R_A, CMD_B. Alternatively, take the I/Os from the folder containing the predefined I/Os in the library and/or from the plant and connect them to the interface blocks.
Function
Performs temperature control for the chilled water flow temperature.
When the function is switched on (the cooling generation plant is "On") and the optional storage tank needs to be charged, the "power control and compensation" logic in the plant is activated and is ready to receive demands for more or less power.
Chilled water flow temperature control details: the minimum value from the flow and return temperature sensors is compared to the setpoint (analog configuration value). If a deviation exceeds the tolerable zone, a signal that demands more or less power ("Step up" or "Step down") is generated (StepUpDn21).
The setpoint for the chilled water temperature control is reduced by a small offset defined by an analog configuration value. The slightly lower setpoint for the chilled water temperature is sent to the energy generator(s).
The logic for chilled water temperature control has one fixed setpoint. The refrigeration machines and the chilled water system are usually designed for a defined temperature level and should not be influenced by consumers.
Use this function even for a single energy generator with stages (2-stages or 8-stages).
This program block has the following optional functions:
Option: Chilled water storage tank
Controls the charging state of a chilled water storage tank (with 4 temperatures) (CrgReqStk21)
Option: Temperature difference calculation for step-down command
Generates a step-down request for the power control and compensation logic if the main temperature difference (main flow temperature – main return temperature) is too small and falls below a certain setpoint (TDiffStepDn21).
Option: Controller for additional setpoint shift for fixed-mode energy generators
The operating mode "Fixed" is for energy generators with their own (external) control unit which only receive a setpoint. The operating mode "Fixed" appears after the operating mode "On" in the profile table. It ensures that one energy generator maintains its nominal power and that another energy generator that is switched on later modulates to maintain the main flow temperature.
A PID controller compares the main flow temperature to its setpoint and increases its output (in %) if there is a deviation. The energy generators read this signal and increase the local setpoints for the energy generators with the operating mode "Fixed". This keeps the energy generators at their nominal power and prevents modulation.
Name | Description | Type | Alarm / Notification class | Trend / Type | |
|---|---|---|---|---|---|
TMnFlCns | Main flow temperature consumer side | AI: Analog input | No | Yes, 2 | |
TMnRtGen | Main return temperature generation side | AI: Analog input | No | Yes, 2 | |
SpTChw | Setpoint chilled water temperature | ACnfVal: Analog configuration value | N/A | Yes, 4 | |
DiffSpTEgGen | Temperature difference setpoint for energy generator | ACnfVal: Analog configuration value | N/A | No | |
StepUpDn | Step up/down | N/A | N/A | ||
Name | Description | Type | Alarm / Notification class | Trend / Type | |
|---|---|---|---|---|---|
SpTHw | Setpoint hot water temperature | SpTHw: Setpoint hot water temperature | No | Yes, 2 | |
ChwStk | Chilled water storage tank | [CrgReqStk21] Charge request storage tank, 4 temperature sensors | N/A | N/A | |
TDiffStepDn | Temperature difference for step down | N/A | N/A | ||
SpTShEgGenCtr | Controller for temperature setpoint shift for energy generator | Ctr: Controller | N/A | N/A | |