Boiler control with the heating control strategy

Each boiler in a group needs a position number, defined by parameter SYS-01, starting with “1” and ascending without gaps.


In a heating system with multiple boilers, the boilers can be arranged into groups and will be controlled in sequence or parallel, according to the configuration of the heating control strategy.


With the parameters ST1-01 and ST1-02 the minimum on and off times of Stage1Cmd are defined. The parameters ST1-03 and ST1-04 define the Stage1Cmd blocking times for the next stage or boiler on or off. For Stage2Cmd these parameters are respectively ST2-01, ST2-02, ST2-03 and ST2-04.

The figure shows the operation of the blocking signal for a staged heat generators:

Fig. 2.   Blocking times for a staged heat generator

When the minimum on time (ST1-02 or ST2-02) is over and the heat generator stage switches off, the blocking time (ST1-04 or ST2-04) to switch on other heat generators will be reset.

When the minimum of time (ST1-03 or ST2-04) is over and the heat generator stage switches on, the blocking time (ST1-05 or ST2-05) to switch off other heat generators will be reset.

Table 8.   Blocking signal values

Value DISP-01

Function

0; 1

no blocking

2

blocking increasing the number of stages

3

blocking decreasing the number of stages

4

blocking increasing and decreasing the number of stages


When a boiler is in operation, the boiler specific minimum supply temperature, defined by parameter BST-04 is transmitted to the heating control strategy macro, to maintain the required boiler temperature limits within the whole heating system.

When a boiler is in operation, the boiler specific minimum return temperature, defined by input “RetTempSp” is transmitted to the heating control strategy macro, to maintain the return temperature only if minimum return temperature control was configured (SYS-02 = 1).

For details of grouping, sequencing and cyclic changeover of the heat generators, please refer to the documentation of the heating control strategy.

Table 9.   Parameter List

Description

Value Range

Default Value

Unit

BST-04: minimum boiler supply temperature

0...500

10

°C

ST1-02: minimum on time stage 1

0...3600

240

sec

ST1-03: minimum off time stage 1

0...3600.

240

sec

ST1-04: blocking time to switch on next stage or boiler

0...3600

600

sec

ST1-05: blocking time to switch off next stage or boiler

0...3600

300

sec

ST2-02: minimum on time stage 2

0...3600

240

sec

ST2-03: minimum off time stage 2

0...3600

240

sec

ST2-04: blocking time to switch on next stage or boiler

0...3600

300

sec

ST2-05: blocking time to switch off next stage or boiler

0...3600

300

sec

SYS-01: position number

1...16

1

-

SYS-02: configuration boiler type

1 = minimum return temperature control

2 = maximum return temperature control

3 = no return temperature control

1...3

3

-