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 the input value is "999".

To enable this function, connect:

Fixed RWT Setpoint

The return temperature setpoint is a fixed value as defined by the datapoint connected to the input "PriRetTempSp" if
RWT-04 = 1. During legionella protection, the primary return temperature setpoint will be increased by the value of the parameter RWT-01.

Table 3.   Parameter List

Description

Value Range

Default Value

Unit

RWT-01: return water setpoint increase during legionella protection

0...50

20

K

RWT-04: return water control configuration

1 = fixed setpoint

2 = outside air temperature compensated

3 = DST compensated

1...3

1

-


RWT Setpoint with OAT Compensation

The return water temperature setpoint will be compensated by the outside air temperature if RWT-04 = 2. The relationship between the calculated return temperature setpoint "CalcRWTempSp" and the outside air temperature is shown in the next figure. To disable this function, set RWT-04 to a value different from 2 or set RWT-03 = 0.

During legionella protection, the primary return temperature setpoint will be increased by the value of the parameter RWT-01.

Fig. 5.   RWT Setpoint with OAT Compensation


Table 4.   Parameter List

Description

Value Range

Default Value

Unit

RWT-01: return water setpoint increase during legionella protection

0...50

20

K

RWT-03: return water setpoint increase at high DST or low OAT

0...50

20

K

RWT-04: return water control configuration;

1 = fixed setpoint

2 = outside air temperature compensated

3 = DST compensated

1...3

1

-

OAT-02: minimum outside air temperature

-50...50

-10

°C

OAT-03: maximum outside air temperature

-50...50

20

°C


RWT Setpoint with DST Compensation

The return water temperature setpoint will be compensated by the district heating supply temperature (DST) if RWT-04 = 3. The relationship between the calculated return temperature setpoint "CalcRWTempSp" and the district heating supply temperature is shown in the figure below.

If the DST sensor is connected to the input "DistrHtgSupTemp", the return temperature setpoint will be compensated by DST. To disable this function, set RWT-04 to a value different of 3 or RWT-03 = 0.

During legionella protection, the primary return temperature setpoint will be increased by the value of the parameter RWT-01.

Fig. 6.   RWT Setpoint with DST Compensation


Table 5.   Parameter List

Description

Value Range

Default Value

Unit

RWT-01: return water setpoint increase during legionella protection

0...50

20

K

RWT-03: return water setpoint increase at high DST or low OAT

0...50

20

K

RWT-04: return water control configuration

1 = fixed setpoint

2 = outside air temperature compensated

3 = DST compensated

1...3

1

-

DST-01: minimum district supply temperature

0...200

75

°C

DST-02: maximum district supply temperature

0...200

115

°C