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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.
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