Danfoss DHP-AX Installation And Service Instructions Manual page 27

The integral value is a measurement of the surface under the time axle and is expressed in degree minutes. The
figure below shows the factory settings for the integral values that the heat pump has. When the integral value
has reached the set value for INTEGRAL A1, the compressor starts and if the integral value does not drop but
continues to rise, the auxiliary heater starts when the integral value has reached the set value for INTEGRAL
A1+A2.
Integral
Heat surplus
(Heat demand)
Compressor start (A1)
Aux. heater start
(A1+A2)
No operation
The calculation of the integral value stops during heat stop. Integral value calculation resumes two minutes
after completed hot water production to give the heating system time to stabilise the temperature.
11.5.8 HYSTERESIS
In order to start the heat in advance during sudden changes of the heat demand, there is a value, HYSTERESIS,
which controls the difference between the actual supply temperature, t1 and the calculated supply tempera-
ture, t2. If the difference is the same or greater than the set HYSTERESIS value (x), i.e. there is a heat demand, or
the heat demand disappears, quicker than the usual integral calculation, the integral value is forced to either
the start value INTEGRAL A1 or to the stop value 0°min.
SUPPLY TEMP.
INTEGRAL
INTEGRAL A1
INTEGRAL A2
Heating deficit
Aux. heater
Compressor
Figure 23: Starting and stopping heat pump operation based on integral values.
HYSTERESIS
(∆t) ≥ x
Compressor start
(-60)
Figure 24: Conditions for HYSTERESIS to force the integral value to change.
Heat surplus
Compressor stop (≥0)
Compressor start
(A1)
Aux. Heater stop Aux. heater start
(latest by A1) (A1+A2)
No operation
t
1
t
HYSTERESIS
(∆t) ≥ x
Compressor stop
(0)
VMBMH302
INTEGRAL A1
INTEGRAL A2
Aux. heater
Compressor
2
TIME
Time
Heat pump operation
Service – 27