[Pu27] Pump, pressure-controlled VSD bypass

Program block, name / node subtype: [Pu27] Pump, pressure-controlled VSD bypass

Library hierarchy: Universal equipment

Family: Pu

Project tree	Diagram

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

Controls a variable speed pump and performs pressure control.

The program block "Variable speed control bypass" (VsdBy21) performs a control of the pump with constant speed in the event of a problem with the variable speed drive.

There is a filter function for the measured value for pressure. However, its time constant is set to a short value, e.g., 1 second. The reason for this is that there is already a pre-filtering with the setting for the COV for the predefined IO, e.g., 5 kPa, and, in addition, the PID controller has a preset neutral zone, e.g., 6 kPa.

A minimum speed, e.g., 10 %, is preset with the property "Controller output minimum" of the BACnet object of the controller. The speed can be adjusted.

This program block has the following optional functions:

Option: Command (1xBO)

Enables the variable speed drive.

Some motor control units, e.g., some EC motors, only need an analog signal, e.g., 0-10 V, and do not need a binary output.

Option: Fault (1xBI)

Reads the fault signal from the pump control unit and generates an alarm.

Option: Feedback (1xBI)

Reads the feedback signal, e.g., from a pump control unit, and generates an alarm if feedback is missing when the pump must run.

A parameter in the program defines the source for the feedback (from the VSD or fan control unit or from an external source):

0 = Feedback from the VSD

1 = Feedback from external source

Option: Flow detector (1xBI)

Reads the signal from a flow detector and generates an alarm if flow is missing when the pump must run.

Option: Kick function

Prevents standstill damage by generating a pulse that starts the pump at a configured time with a defined pulse length after a minimum off time has elapsed.

This is configured in the program.

Option: Maintenance switch (1xBI)

Reads the signal from the maintenance switch and generates an alarm. If active, then the outputs of the pump are stopped with very high priority (priority 2).

Mandatory elements

Name	Description	Type	Alarm / Notification class	Trend / Type
VsdBy	Variable speed control (VSD) bypass	[VsdBy21] Variable speed control bypass	N/A	N/A
DiffP	Differential pressure	AI: Analog input	No	Yes, 2
Spd	Speed	AO: Analog output	No	Yes, 2
PCtr	Pressure controller	Ctr: Controller	N/A	N/A
SpDiffP	Setpoint differential pressure	ACnfVal: Analog configuration value	No	No

See also

Optional elements

Name	Description	Type	Alarm / Notification class	Trend / Type
Cmd	Command	BO: Binary output	No	Yes, 4
Flt	Fault	BI: Binary input	Yes, 4/5	No
MntnSwi	Maintenance switch	BI: Binary input	Yes, 5	No
FlDet	Flow detector	BO: Binary output	Yes, 4	No
Fb	Feedback	BI: Binary input	Yes, 4	No

See also

Further options

Description
Kick function