Danfoss DHP-AX User Manual page 16

3.4.8 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 sup-
ply temperature, t1 and the calculated supply temperature, 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 inte-
gral value is forced to either the start value INTEGRAL A1 or to the stop value 0°min.
SUPPLY TEMP.
INTEGRAL
Figure 9: Conditions for HYSTERESIS to force the integral value to change.
3.4.9 DEFR CURVE
To start defrosting the outdoor unit, the control system makes a calculation using
the temperature of the refrigerant return and the outdoor temperature.
What guides the calculation is a linear defrosting curve that can be set so that the
heat pump and outdoor unit work optimally. The setting of three different values
can be changed: DEFR CURVE 0 , DEFR CURVE –20 and OUTDOOR STOP. The defrost-
ing sequence starts when the temperature of the refrigerant return reaches the set
parameter value at an outdoor temperature somewhere along the set defrosting
curve.
The two parameters that are mainly changed are DEFR CURVE 0 and DEFR CURVE
-16. The numbers behind the DEFR CURVE display what outdoor temperature the
setting is for, that is to say at 0°C for DEFR CURVE 0 and -16 for DEFR CURVE -16. The
DHP-AX – 16
HYSTERESIS
(∆t) ≥ x
Compressor start
(A1)
VUBMI102
t1
t2
HYSTERESIS
(∆t) ≥ x
Compressor stop (0)
TIME