Primary Return Temperature Limitation

In district heating systems or if the heat generators are condensing boilers, it is required and useful to limit the primary return temperature. This function is disabled when you add this macro to your control loop, since the default input value is "999".

To enable this function, connect:

During legionella protection, the primary return temperature setpoint will be increased by the value of the parameter RWT-01. Depending on the calculated P-band (RWT-02) and the primary return temperature setpoint, the control signal varies from the valve position limit 0 ...100%, as shown in the next figure.

Fig. 5.   Primary Return Temperature Limitation


Table 6.   Parameter List

Description

Value Range

Default Value

Unit

RWT-01: return water setpoint increase during legionella

0...50

20

K

RWT-02: P-band return temperature control

1...20

10

K

VLV-01: valve position limit

0...100

100

%