Installation manual
12
1.2
same time, the costs for tapping the heat source system are
lower.
Refer to the relevant chapters for further information on how to
dimension heat source systems for brine-to-water and water-to-
water heat pumps.
1.2 Heat Pumps for New Systems
1.2.1 Calculating the heat consumption of the building
The maximum hourly heat consumption
h
is calculated
according to the respective national standards. It is possible to
approximately estimate the heat consumption using the living
space A (m
2
) that is to be heated:
Table 1.1: Estimated specific heat consumption values
1.2.2 Determining the flow temperatures
When dimensioning the heat distribution system of a heat pump
heating system, it should be borne in mind that the required heat
consumption should be assigned on the basis of the lowest
possible flow temperatures, because every 1 °C reduction in the
flow temperature yields a savings in energy consumption of
approx. 2.5 %. Extensive heating surfaces, e.g. underfloor
heating, are ideal. The required flow temperature should
generally be 55 °C max. to enable the use of low-temperature
heat pumps. If higher flow temperatures are necessary, medium
or high-temperature heat pumps must be used (Chap. 1.1.3 on p.
11).
1.2.3 Selecting the heat source
The decision as to whether air, brine (ground heat collector,
borehole heat exchanger) or water (well system) should be used
as the heat source should be made on the basis of the following
factors.
a) Investment costs
In addition to the costs for the heat pump and the heating
system (radiators and circulation pump), the investment
costs are heavily influenced by the costs of tapping the heat
source.
b) Operating costs
The expected annual performance factors of the heat pump
heating system have a large influence on the operating
costs. These are primarily affected by the type of heat pump,
the average heat source temperature and the required
heating flow temperatures.
NOTE
The annual performance factors which can be expected for air-to-water
heat pumps are lower than for water and geothermal systems. However,
the costs for tapping the heat source system are also lower.
1.3 Additional Power Requirements
1.3.1 Shut-off times of the utility company
Most utility companies offer special agreements with a lower
electricity tariff if heat pumps have been installed. According to
the German Federal Tariff Ordinance, the utility company may
offer such an agreement if it is able to switch off and block heat
pumps at times of peak demand in the supply network.
The heat pump is then no longer available for heating the house
during these shut-off times. Therefore, surplus energy must be
produced during the periods in which the heat pump is not
available for use. Hence, the heat pump should be
overdimensioned to allow for this.
Utility company shut-off times normally last up to 4 hours a day,
which must be allowed for with a factor of 1.2.
Dimensioning
The calculated heat consumption values for heating and
domestic hot water preparation should be added together.
Unless a second heat generator is additionally used during the
shut-off time, the sum of the heat consumption values must be
multiplied by the dimensioning factor f:
Basis of the calculation:
Table 1.2: Dimensioning factor f for taking shut-off times into consideration
The existing heat storage capacity of solidly built houses,
particularly those with underfloor heating, is normally sufficient to
also bridge longer shut-off times with only a small loss of comfort
so that it is not necessary to use a second heat generator (e.g.
boiler). However, an increase in output of the heat pump is
necessary because of the need for reheating the storage mass.
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= 0.03 kW/m
2
Low-energy house
= 0.05 kW/m
2
Acc. to thermal insulation ordinance 95 and/
or the EnEV minimum insulation standard
= 0.08 kW/m
2
For a house with normal thermal insulation
(built approx. in 1980 or later)
= 0.12 kW/m
2
For older walls without special thermal
insulation
T
T
T
T
Blocking time (total) Dimensioning factor
2 h 1.1
4 h 1.2
6 h 1.3
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