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HDG HYDRONIC CONTROL FUNCTIONS
BASIC FUNCTIONS OF THE
HEATING CIRCUIT CONTROL
The heating circuit control always operates at a characteristic heating
curve controlled by the outdoor air temperature. For each heating
system, the characteristic heating curve is used to calculate the
supply water temperature which is appropriate for the current
outdoor temperature. Other factors which influence the calculated
water temperature are the steepness of the characteristic heating
curve, the correction for this (parallel shift) and the preset value for
the room temperature.
If the heating circuit control is operating, room temperature will be
adjusted to a preset daytime or night-time value.
Example:
Outdoor temperature -5 °C
Steepness 1.6
Parallel shift 5°C
With these presumed values, you can see in Figure 3/5 - Diagram of
the temperature of water leaving the boiler that the heating circuit
supply temperature of the water is 67 °C.
If an indoor thermostat unit is also connected, the comparison
between the preset and the actual room temperature and the room
influence factor are also included in the calculation of the required
water temperature leaving the boiler. The temperature difference is
multiplied by the room influence factor and is then added to the
preset room temperature. The room influence factor expresses how
strongly any deviation of the room temperature should affect the
water temperature leaving the boiler.
If no indoor thermostat unit is connected, the preset day and night
temperatures are used for the calculation.
O
UTDOOR TEMPERATURE
SWITCH-OFF
If the outdoor temperature exceeds the preset room temperature or
the preset outdoor switch-off temperature, the status of the heating
circuit changes to OFF.
Figure 3/5 - Diagram of the temperature of water leaving the boiler
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