Danfoss DHP-AX Installation And Service Instructions Manual page 26

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 adjusting the curve
at three outdoor temperatures: -5°C, 0°C, +5°C. This function will allow you to increase or reduce the setpoint
value for the supply line temperature, without affecting the rest of the heat curve, at three specific outdoor
temperatures. If, for example, the outdoor temperature is -5°C, the supply temperature will change gradually
between 0°C and -10°C, maximum adjustment being reached at -5°C. The figure above shows the adjusted
CURVE -5. The adjustment can be seen in the graph in the form of a bump.
You can choose to adjust the heat curve individually at three specified outdoor temperatures: -5°C, 0°C and
+5°C. The supply temperature can be changed by plus/minus 5 degrees.
11.5.4 HEAT STOP
The HEAT STOP function automatically stops all production of radiator heat when the outdoor temperature is
equal to, or higher than, the value entered for heat stop.
When the heat stop function is activated, the circulation pump will be turned off - except when hot water is
being produced. The circulation pump will be "exercised" for 1 minute per day. The factory set value for activat-
ing heat stop is an outdoor temperature of 17°C. If the heat stop function is active, the outdoor temperature
must drop 3°C when setting, before the heat stop stops.
11.5.5 MIN and MAX
The MIN and MAX values are the lowest, respectively highest set point values that are allowed for the supply
temperature.
Adjusting the minimum and maximum set point value for the temperatures is particularly important if your
home has under floor heating.
If your house has under floor heating and parquet floors, the supply temperature must not be too high.
Otherwise there is a risk that the parquet floors might be damaged. If you have under floor heating and stone
floors, MIN should not be too low in order to achieve a comfortable floor temperature in the summer time
when heating is not required. A possible solution to obtain optimum temperatures is to use a shunt group for
under floor heating.
If your house has a basement, the MIN value should be adjusted to a suitable temperature for the basement in
summer. A condition for maintaining the heat in the basement in the summer is that all radiators have thermo-
stat valves that switch off the heat in the rest of the house. It is extremely important that the heating system
and the radiator valves are trimmed correctly. As it is usually the end customers themselves who have to carry
out trimming, remember to inform them how to carry it out correctly. Also remember that the value for HEAT
STOP needs adjusting upwards for summer heating.
11.5.6 TEMPERATURES
The heat pump can display a graph showing the history of the various sensors' temperatures and you can see
how they have changed over 60 measurement points in time. The time interval between the measurement
points can be adjusted between one minute and one hour, factory setting is one minute.
History is available for all sensors, but only the set value is shown in the display for the room sensor. The inte-
gral value that may appear is the heating system's energy balance.
11.5.7 INTEGRAL
The heat demand in the house depends on the season and weather conditions and is not constant. The heat
demand can be expressed as temperature difference over time and can be calculated giving an integral value as a
result (heat demand). To calculate the integral value, the control system uses several parameters.
A heat deficit is needed to start the heat pump, and there are two integral values, A1 (default value = -60), which
starts the compressor and A2, (default value = -600), which starts the auxiliary heater. During heat production, the
deficit reduces and when the heat pump stops, the inertia in the system causes a surplus of heat.
26 – Service
Supply temperature
Figure 22: The adjusted curve at -5°C
Local higher supply temperature
at -5°
VMBMH302
Outdoor temperature