Minimum boiler return temperature control

The boiler minimum return temperature control is switched off by default due the value “999” at the input “RetTempSp”.

You can enter another fixed value  as a default at the input “RetTempSp” or you can connect a time schedule or any other program code to override this input.

The boiler return temperature control can be defined as a P- or PI-controller.

Depending on the minimum boiler return temperature setpoint, the P-band and the I-time, respectively defined by the input “RetTempSp” and the parameters BRT-01 and BRT-02, the output signal to the boiler valve varies from 0...100%. If the I-time BRT-02 is set to “0”, then the valve control is according to left figure; if the I-time BRT-02 is set to a value greater than ”0”, the right figure shows the valve control. If no boiler release is available the boiler valve will be closed.


Fig. 8.   Minimum boiler return temperature control

Table 15.   Parameter List

Description

Value Range

Default Value

Unit

BRT-01: P-band boiler return temperature

1...500

100

K

BRT-02: I-time boiler return temperature

0…3600

30

sec