Installation manual

14
1.3.4.2
Experience has shown that a heat pump should be selected
which cuts the heating characteristic curve for a limit temperature
(bivalence point) of approx. -5 °C.
According to the DIN 4701 T10 standard, this yields a 2 % ratio
for the second heat generator (e.g. heating element) when
operated as a bivalent-parallel system.
Fig. 1.3 on p. 14 shows the annual characteristic curve of the
external temperature in Essen, Germany. According to this, there
are less than 10 days annually with an external temperature
under -5 °C.
Fig. 1.3: Annual characteristic curve: Number of days on which the external
temperature is below the specified value
Example for Table 1.5 on p. 14:
A bivalence point of -5 °C yields a heat pump proportion of
approx. 98 % for a bivalent-parallel (mono energy) mode of
operation.
Table 1.5: Coverage ratio of the heat pump of a mono energy system or a system operated as a bivalent system according to bivalence point and mode of operation
(source: Table 5.3-4 DIN 4701 T10)
1.3.4.2 Dimensioning example for an air-to-water heat pump
The heat pump is dimensioned on the basis of the heat
consumption of the building in relation to the outside temperature
(simplified as a straight line) in the heat output diagram and the
heat output curve of the heat pump. The building's heat
consumption in relation to the external temperature is entered on
the basis of the selected room temperature (corresponding to the
external temperature point 1) on the horizontal axis (x axis) for
the calculated heat output (point 2) for the standard external
temperature according to national standards.
Fig. 1.4: Heat output curves for two air-to-water heat pumps with different
heat outputs for flow temperatures of 35 °C and a building heat
consumption in relationship to the outside temperature
The approach is illustrated by the example from Fig. 1.4 on p. 14
with a total heat consumption for the house of 11.0 kW at a
standard outside temperature of -16 °C and a selected room
temperature of +20 °C. The diagram shows the heat output
curves of two heat pumps at a hot water flow temperature of
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Bivalence point [°C] -10-9-8-7-6-5-4-3-2-1012345
Coverage ratio [-] for
biv.-paral. operation
1.00 0.99 0.99 0.99 0.99 0.98 0.97 0.96 0.95 0.93 0.90 0.87 0.83 0.77 0.70 0.61
Coverage ratio [-] for
biv.- altern. operation
0.96 0.96 0.95 0.94 0.93 0.91 0.87 0.83 0.78 0.71 0.64 0.55 0.46 0.37 0.28 0.19
 Mono energy mode of operation:
Heat pump with electric heating element
 Heating system with a maximum flow
temperature of 35 °C
 Selected heat consumption of the building to
be heated
9.0 kW
 Additionally selected heat consumption for
domestic hot water preparation and
swimming pool heating
1.0 kW
 (heat consumption of the building +
additional heat consumption) x factor f from
Table 1.2 on p. 12 (with e.g. a 2-h shut-off
time) = (9.0 kW + 1 kW) x 1.1 =
11.0 kW
= required heat output of the heat pump on the
basis of the standard outside temperature
according to national standards.
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