Maximum Return Temperature Control

This function is required in case of district heating applications. The heating circuit return water temperature (RWT) can be limited by a maximum setpoint, in order to override the heating valve output to close, if the return water temperature becomes too high. The relationship between the calculated return water setpoint and the outside air temperature is shown in the next figure. The calculated return temperature setpoint is displayed in the setting DISP-04 and the macro output "CalcRetTmpSp".

Fig. 13.   Return water temperature setpoint

Depending on the P-band RWT-05, the I-time RWT-06 and the calculated return water temperature setpoint, the control signal varies from 0...100% as shown in the next figure.


Fig. 14.   Return water temperature control

Table 17.   Parameter List

Description

Value Range

Default Value

Unit

RWT-01: min. OAT RWT control

-50…150

-10

°C

RWT-02: max. OAT RWT control

-50…150

10

°C

RWT-03: low setpoint

0…150

65

°C

RWT-04: high setpoint

0…150

85

°C

RWT-05: P-band RWT control

1…50

10

K

RWT-06: I-time RWT control

0…3600

0

sec

DISP-04: calculated return water temperature setpoint

0…150

-

°C