Configuring The Dual Mode Point - Wolf BWL-1 S Installation And Operating Instructions Manual

Configuration example
Central heating demand (building heat load) to DIN 4701 or EN 12831 of 7.7 kW. A DHW demand for 4 people (0.25 kW/person)
and a standard outside temperature of -16 °C are assumed.
The power supply utility specifies a blocking time of 2 x 2 hours. The blocking time factor Z is 1.1.
Using these figures, the required heat pump output is calculated as follows:
.
Q
.
Q
.
Q
.
HP
Q
.
B
Q
.
DHW
Q
.
E-rod
Q
HP,Tn
Z
Diagram for calculating the dual
mode point and the output of the
electric heating rod
.
Q
HP
1
9.6
.
Q
E-rod
6
.
5.6
Q
HP,Tn
Standard outside temperature
As can be seen from the diagram, the theoretical heating output for the standard design point is approx. 5.6 kW. Since a 4 kW
heater rod is also installed, the maximum available heating output is 9.6 kW at an outside temperature of -16 °C.
This results in a dual mode point of approx. -4 °C.
The closer the dual mode point gets to the standard outside temperature, the lower the proportion of booster heating.
As a rule, the booster heater is responsible for approx. 30 - 60 % of the required heating output. Though the proportion of output
attributable to the booster heater is relatively large, the proportion of work is only approx. 2 - 5 % of the annual heating load.
In the example shown, a DHW cylinder with a water capacity of 300 litres can meet the daily requirements of a 4-person
household (detached house, high demand of 4 x 70 litres/day = 400 l DHW cylinder).
No changes would be made to the selected heat pump type in this example.
82
33. Configuring the dual mode point
.
.
= (Q + Q ) x Z
HP B DHW
.
.
= Q - Q
E-rod HP HP,Tn
:
Required peak output of the heat pump system
:
Building heat load (building heat demand, central heating demand)
:
Output demand for DHW heating
:
Heater rod output
:
Heating output of heat pump for standard design point
:
Blocking time factor
5
4
2
-16 -4
Dual mode point
= (7.7 kW + 1.0 kW) x 1.1 = 9.6 kW
= 9.6 kW - 5.6 kW = 4.0 kW
Max. compressor speed
3
Heating limit temperature
Nominal compressor speed
Min. compressor speed
Air inlet temperature [°C]
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