[CGen21] Refrigeration generation, 1 chiller with external compressor control (on/off command, setpoint, feedback, common fault), chilled water storage tank

Plant example CGen21 has a chiller with external cooling group control, compressor control and a chilled water storage tank.

Functions

Collects cooling requests
Charges storage tank
Controls chiller

Plant diagram

Components

Chilled water storage tank with four sensors
Interface to external cooling group control
Hydraulics for evaporator group
Hydraulics for condenser group
Recooling command

Components and functions

Components and functions of the plant example:

Component	Function	BACnet object
Gas	Gas detector Switches the plant off.	[BI] Gas detector
	Fire detection contact Switches the plant off.	[BI] Fire detection contact
	Operating mode switch Switches the plant to: Auto \| Off \| On	[MI] Operating mode switch
	Manual operating mode selection Switches the plant to: Auto \| Off \| On	[MCnfVal] Manual operating mode selection
	Present operating mode Reports the present operating mode: Off \| On Plant operating modes and control sequence	[MCalcVal] Present operating mode
	Reason for present operating mode Reports the reason for the present operating mode: Exception \| Operating mode switch \| Manual operating mode selection \| Cooling request \| Request from chilled water storage tank	[MCalcVal] Reason for present operating mode
	Cooling request Acquires cooling demand. The plant switches on if one or more cooling requests are pending and the chilled water storage tank is discharged. The plant switches off only after the chilled water storage tank is charged.
	Setpoints Cooling generation has an adjustable setpoint for chilled water temperature in the chilled water storage tank. External cooling group control in the chiller controls the outlet temperature on the evaporator to a setpoint reduced by the delta setpoint for chilled water temperature.	[ACnfVal] Chilled water temperature setpoint [ACnfVal] Chilled water temperature delta setpoint

Chiller

Component	Function	BACnet object
	Chiller Includes evaporator hydraulics, interface to external compressor control and condenser hydraulics.	Chiller (Folder)
	Condenser Controls condenser hydraulics.	Condenser (Folder)
	Outlet temperature on the condenser Measures the outlet temperature.	[AI] Outlet temperature
	Inlet temperature on the condenser Measures the inlet temperature.	[AI] Inlet temperature
	Setpoint for minimum inlet temperature to the condenser Specifies the minimum inlet temperature.	[ACnfVal] Min. inlet temperature setpoint
	Pump	Pump (Folder)
	Command Switches on/off the pump as needed.	> [BO] Command
	Fault message Reports faults. Switches the plant off.	> [BI] Fault
	Feedback message Monitors feedback and switches off the plant.	> [BI] Feedback
	Mixing valve At the inlet, it mixes the required amount of water from the outlet to achieve the desired inlet temperature.	Mixing valve (Folder)
	Temperature controller Controls the inlet temperature.	> [Controller] Temperature controller
	Positioning 0% = Bypass … 100% = Through-port	> [AO] Position
	Request to recooling Binary request to recooling	> [BO] Recooling command (Located in condenser)
	Interface to external cooling group control	External cooling group control (Folder)
	Release Release for external control	> [BO] Command
	Setpoint for the outlet temperature at the condenser Transfers a temperature setpoint to external control.	> [AO] Temperature setpoint
	Fault message Reports faults. Switches the plant off.	> [BI] Fault
	Feedback, binary Counts the operating hours.	> [BI] Feedback
	Evaporator Controls evaporator hydraulics.	Evaporator (Folder)
	Flow monitoring on evaporator Monitors flow on the evaporator. Switches the plant off.	[AI] Flow detector
	Outlet temperature on evaporator Measures the outlet temperature.	[AI] Outlet temperature
	Inlet temperature on evaporator Measures the inlet temperature.	[AI] Inlet temperature
	Pump	Pump (Folder)
	Command Switches on/off the pump as needed.	> [BO] Command
	Fault message Reports faults. Switches the plant off.	> [BI] Fault
	Feedback message Monitors feedback and switches off the plant.	> [BI] Feedback
	Mixing valve At the inlet, it mixes the required amount of water from the outlet to achieve the desired chilled water temperature setpoint at the outlet.	Valve (Folder)
	Temperature controller Controls the outlet temperature.	> [Controller] Temperature controller
	Positioning 0% = Bypass … 100% = Through-port	> [AO] Position

Chilled water storage tank

Component	Function	BACnet object
	Chilled water storage tank Chilled water storage tank with four sensors and charging logic. Temperature (1) is the highest and temperature (4) the lowest temperature measurement. Charge: The storage tank is discharged and charging is required if temperature (3) is above the chilled water temperature setpoint. Charged: The storage tank is charged if temperature (1) has a switching difference, e.g. 1K, below the chilled water temperature setpoint.	Chilled water storage tank (Folder) [ACalcVal] Present temperature setpoint [AI] Temperature (1) [AI] Temperature (2) [AI] Temperature (3) [AI] Temperature (4)

Component

Function

BACnet object

Chilled water storage tank

Chilled water storage tank with four sensors and charging logic.

Temperature (1) is the highest and temperature (4) the lowest temperature measurement.

Charge:

The storage tank is discharged and charging is required if temperature (3) is above the chilled water temperature setpoint.

Charged:

The storage tank is charged if temperature (1) has a switching difference, e.g. 1K, below the chilled water temperature setpoint.

Chilled water storage tank (Folder)

[ACalcVal] Present temperature setpoint

[AI] Temperature (1)

[AI] Temperature (2)

[AI] Temperature (3)

[AI] Temperature (4)

Functions and diagrams

Chiller with external control of the compressor, hydraulics for the evaporator and condenser group

Operating modes: Off, on

Components, sequence, and function in CMDSEQ_B

Plant operating mode	Component
	Cds	Evp	RfCrtExtCtl
Off	Off	Off	Off
On	On	On	On

Sequences
Start sequence	1	2	3
Start function	Delay	Delay	AND (Group with next aggregate)
Start delay	30 s	30 s	-

Stop sequence	3	2	1
Stop function	AND (Group with next aggregate)	Delay	Delay
Stop delay	-	30 s	30 s

[CMDSEQ_B] Command sequence for binary

Start sequence

The hydraulics for the condenser group switch on with a delay of 30 seconds (function Delay).
The hydraulics for the evaporator group switch on with a delay of 30 seconds (function Delay).
External cooling group control switches on.

Stop sequence

External cooling group control switches off with a delay of 30 seconds (function Delay).
The hydraulics for the evaporator group switch off with a delay of 30 seconds (function Delay).
The hydraulics for the condenser group switch off.

Controller

Name	Description	Object type	Default value
Ch'Evp'Vlv'TCtr	Temperature controller for chiller, evaporator, valve Controls the evaporator outlet temperature.	Controller	N/A
Ch'Evp'Vlv'TCtr	The temperature controller acts as a PI controller and compares the temperature setpoint chiller [SpTChw] against the outlet temperature on evaporator ['Evp'T] and calculates the modulating control for valve position [Ch'Evp'Vlv'Pos]. The following controller variables are preset: - Controller gain: 2.5 [%/K] - Integral action time Tn: 120 [s]
Ch'Cds'Vlv'TCtr	Temperature controller for chiller, evaporator, valve Controls the condenser inlet temperature.	Controller	N/A
Ch'Cds'Vlv'TCtr	The temperature controller acts as a PI controller and compares the minimum inlet temperature setpoint on the condenser [Ch'Cds'SpTInMin] against the inlet temperature on the condenser [Ch'Cds'TIn] and calculates the modulating control for valve position [Ch'Evp'Vlv'Pos]. The following controller variables are preset: - Controller gain: 2.5 [%/K] - Integral action time Tn: 120 [s]

Plant operating modes and control sequence

Plant operating modes:

Off (1)
On (2)

The operating modes are reported on [MCalcVal] object 'Present operating mode'.

At the same time, the reason for the present operating mode is reported to another [MCalcVal] object:

Exception (1)
Operating mode switch (2), resulting from an active (not equal to Auto) operating mode switch
Operating mode (3), resulting from an active (not equal to Auto) manual operating mode selection
Cooling request (4)
Request from chilled water storage tank (5)

There is a normal mode and exception mode.

Normal mode

Sources for normal mode:

[MI] Operating mode switch
[MCnfVal] Manual operating mode selection
[CReq (1)] Cooling demand
Request from chilled water storage tank

In normal mode, in operating mode 'On', the chiller switches on with function block CMDSEQ_B.
[CMDSEQ_B] Command sequence for binary

Exception mode

Sources for exception mode:

Fire detection contact
Gas detector
Chiller faults:

Fault on or missing feedback from the evaporator pump

No flow in evaporator circuit

Fault to external cooling group control

Fault on or missing feedback from the condenser pump

In exception mode, all outputs are switched off directly at priority 5 and the present operating mode is set to 'Off'.

It is reported at input [RpdOff] for CMDSEQ_B on the chiller.

Start-up control and alarm handling

Start-up control (nested chart SttUpAlmHdl)

The following functionality is available for an automatic startup of the plant, e.g. after a loss of power and return of power:

Fixed switch-on delay (can be set on input pin [DlySttUp])
The plant remains off to ensure communications are reliable and cross-check references are triggered. 'Exception' is reported as the reason for the present operating mode.
Automatic acknowledge (2x) of possible pending alarms during a fixed switch-on delay.
Additional adjustable delay for staged plant ramp-up (can be set on input pin [DlyOn])

Alarm handling (nested chart SttUpAlmHdl)

The state of events on the plant is acquired by BACnet object 'Plant state'. The state is mapped on function block CMN_EVT.
[CMN_EVT] Common event

The following functions are available:

Automatic acknowledge (2x) after startup
Alarm acknowledgement with a value object
Alarm indication:
- For pending alarms On
- For unprocessed alarms flashing
Ability to connect the acknowledge button [BI]
Ability to connect to an alarm indication [BO], e.g. an alarm lamp through an output block [BO]
Ability to connect to other alarm handling functions on other plants, e.g. acknowledge button and alarm indication for multiple plants in the same control cabinet

Startup function and alarm handling for flat plants

I/O data points

Name	Description	Type	Signal/connection	State text	Engineering unit
FireDetCont	Fire detection contact Alarm function: Extended (Notification class 7) Reference value: Tripped Time deviation: 0 [s]	BI	NC contact	Normal \| Tripped	N/A
GasDet	Gas detector Alarm function: Extended (Notification class 7) Reference value: Tripped Time deviation: 0 [s]	BI	NC contact	Normal \| Tripped	N/A
OpModSwi	Operating mode switch	MI	N/A	Auto \| Off \| On	N/A
Ch'Cds'TIn	Chiller condenser inlet temperature	AI	LG-Ni1000	N/A	0...100 [°C]
Ch'Cds'TOut	Chiller condenser outlet temperature	AI	LG-Ni1000	N/A	0...100 [°C]
Ch'Cds'Pu'Cmd	Chiller condenser pump command Alarm function: Extended (Notification class 7) Reference value: Ch'Evp'Pu'Fb Time deviation: 10 [s]	BO	NO contact	Off \| On	N/A
Ch'Cds'Pu'Fb	Chiller condenser pump feedback message	BI	NO contact	Off \| On	N/A
Ch'Cds'Pu'Flt	Chiller condenser pump fault Alarm function: Extended (Notification class 7) Reference value: Tripped Time deviation: 0 [s]	BI	NO contact	Normal \| Tripped	N/A
Ch'Cds'Vlv'Pos	Chiller condenser valve position	AO	0...10V	N/A	0...100 [%]
Ch'Cds'ReCCmd	Chiller condenser recooling command	BO	NO contact	Off \| On	N/A
Ch'RfCrtExtCtl'Flt	External cooling group control compressor fault Alarm function: Basic (Notification class 8) Reference value: Tripped Time deviation: 0 [s]	BI	NO contact	Normal \| Tripped	N/A
Ch'RfCrtExtCtl'Fb	External cooling group control compressor feedback message	BI	NO contact	Off \| On	N/A
Ch'RfCrtExtCtl'SpT	External cooling group control compressor temperature setpoint	AO	0...10V	N/A	0...20 [°C]
Ch'RfCrtExtCtl'Cmd	External cooling group control compressor command	BO	NO contact	Off \| On	N/A
Ch'Evp'FlDet	Chiller evaporator flow detector Alarm function: Extended (Notification class 7) Reference value: Tripped Time deviation: 10 [s]	BI	NO contact	Normal \| Tripped	N/A
Ch'Evp'TIn	Chiller evaporator inlet temperature	AI	LG-Ni1000	N/A	0...100 [°C]
Ch'Evp'TOut	Chiller evaporator outlet temperature	AI	LG-Ni1000	N/A	0...100 [°C]
Ch'Evp'Pu'Cmd	Chiller evaporator pump command Alarm function: Extended (Notification class 7) Reference value: Ch'Evp'Pu'Fb Time deviation: 10 [s]	BO	NO contact	Off \| On	N/A
Ch'Evp'Pu'Fb	Chiller evaporator pump feedback message	BI	NO contact	Off \| On	N/A
Ch'Evp'Pu'Flt	Chiller evaporator pump fault Alarm function: Extended (Notification class 7) Reference value: Tripped Time deviation: 0 [s]	BI	NO contact	Normal \| Tripped	N/A
Ch'Evp'Vlv'Pos	Chiller evaporator valve position	AO	0...10V	N/A	0...100 [%]
ChwStk'T(1)	Chilled water storage tank temperature (1)	AI	LG-Ni1000	N/A	0...100 [°C]
ChwStk'T(2)	Chilled water storage tank temperature (2)	AI	LG-Ni1000	N/A	0...100 [°C]
ChwStk'T(3)	Chilled water storage tank temperature (3)	AI	LG-Ni1000	N/A	0...100 [°C]
ChwStk'T(4)	Chilled water storage tank temperature (4)	AI	LG-Ni1000	N/A	0...100 [°C]