York Geysir User Manual page 12

If you increase the CURVE value, the heat curve will become steeper and when you reduce
it, it will become flatter.
The most energy efficient and cost effective setting is achieved by changing the CURVE
value to adjust the temperature in the house to an even and constant temperature. For a
temporary increase or reduction, adjust the ROOM value instead.
ROOM
If you wish to increase or reduce the indoor temperature, change the ROOM value. The
difference between changing the ROOM value and the CURVE value is that the system's
heat curve does not become steeper or flatter if the ROOM value is changed, which the
curve becomes if the CURVE value changes, instead the entire heat curve is moved by 3°C
for every degree change of the ROOM value. The reason that the curve is adjusted 3° is that
an approximate 3° increase in supply temperature is needed to increase the indoor tempera-
ture 1°.
Supply temperature
Figure 8: Changing the ROOM value changes the heat curve upwards or downwards .
The relationship of the supply temperature to outdoor temperature will not be affected. The
supply temperature will be increased or reduced by the same number of degrees all along
the heat curve. that is, the entire heat curve rises or drops instead of the curve gradient
changing.
This method of adjusting the indoor temperatures can only be for a rise or fall.
Sometimes, at outdoor temperatures between -5°C and +5°C, part of the heat curve may
need adjusting if the indoor temperature is not constant. For this reason, the control system
includes a function for adjusting the curve at three outdoor temperatures: -5°C, 0°C, +5°C.
If, for example, the outdoor temperature is -5°C, the supply temperature will change gradua-
lly between 0°C and -10°C, maximum adjustment being reached at -5°C. The figure below
shows the adjusted CURVE -5. The adjustment can be seen in the graph in the form of a
bump.
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ENGLISH
Maximum supply tem-
perature
Outdoor temperature