SDC / DHC
Hydraulic Components
EN2H-0221GE51 R0808
145
7.2.1 On/Off operation of the district heating valve
To always ensure a minimum flow so that the heat meter can
work precisely, pure on/off switching is provided in low load mode.
Code 03 is suitable for this function as shown in the following
diagram.
100 %
100 %
0 %
x
y
a
a Minimum
travel
y Controller
output
x Valve
travel
Para-
meter
Designation
Range
Presetti
ng
Step
Unit
03 Minimum
travel
0 ... 50 10
1
%
Should the secondary flow temperature controller output fall
below the settable minimum travel in % (code 03), two-step
operation begins and the valve is closed. The valve remains
closed until the internal controller output reaches 10% again. If a
10% controller output is reached, the valve opens again to the
minimum travel. If the controller output drops below 10% again,
the valve closes again and the cycle starts from the beginning.
This means that whenever there are demands of up to 10% on
the heat generator the valve is operated in On/Off mode and the
secondary flow temperature is controlled this way.
7.2.2 Continuous
heat
exchanger valve control
If the output of the secondary flow temperature controller rises
above 10%, the PI controller controls the secondary flow