Technical data
Selection and Dimensioning of Heat Pumps for Heating and Cooling 1.2
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1 Selection and Dimensioning of Heat Pumps for Heating and
Cooling
1.1 Calculating the Heat Consumption of the Building
The maximum hourly heat consumption
h
is calculated
according to respective national standards. It is possible to
estimate the approximate heat consumption using the living
space A (m2) that is to be heated:
Table 1.1: Estimated specific heat consumption values for Germany
Dimensioning 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 based on the lowest possible flow
temperatures, because every 1 °C reduction in the flow
temperature for the same heating consumption yields a saving in
energy consumption of approx. 2.5 %. Extensive heating
surfaces such as underfloor heating or fan convectors with
maximum flow temperatures of about 40°C are ideal.
1.1.1 DHW heating
To meet normal requirements regarding comfort, allowance
should be made for a peak hot water consumption of approx. 80-
100 litres per person per day based on a hot water temperature
of 45 °C. In this case, allowance should be made for a heat
output of 0.2 kW per person.
The maximum possible number of persons should be assumed
when dimensioning and any special usage (e.g. whirlpool)
should also be taken into consideration.
The heat pump manager regulates domestic hot water
preparation. It activates hot water preparation depending on
need and the type of operation.
When an electrically-operated flange heater is used in the hot
water cylinder for hot water preparation, this can be used in the
calculation of the design (e.g. -16°C). In this case, the heat
output for DHW preparation should not be added to the heating
load.
Circulation pipes
Circulation pipes immediately provide hot water at the extraction
point, but this also considerably increases the amount of heat
required for hot water heating. The increase in consumption
which should be allowed for is dependent on the runtime, the
length of the circulation pipes and the quality of the pipe
insulation. If a circulation system can not be dispensed with
because of long pipe runs, a circulation pump should be used
which can be activated by a flow sensor, pushbutton, etc. if
required.
ATTENTION!
Circulation pipes increase the number of requests for hot water due to
heat losses. In case of active cooling, every request for hot water causes
an interruption of the cooling operation (see Chap. 7.4.3 on p. 50).
1.2 Method for Calculating the Cooling Requirements of the Building
Cooling systems are used to prevent rooms from overheating
due to the effects of undesired heat loads. The cooling capacity
is determined primarily by the outdoor climate, the requirements
for the indoor environment, the internal and external heat loads,
as well as the orientation and the construction of the building.
ATTENTION!
Due to the strong influence of solar radiation and internal heat loads, it is
not possible to make an estimate of the cooling requirements simply on
the basis of the surfaces to be cooled.
Internal loads include e.g. waste heat from appliances, lighting
as well as the occupants themselves. External loads are
defined as the heat input caused by solar radiation, transmission
heat gains from the surfaces enclosing rooms as well as
ventilation gains caused by the entry of warmer air from outside.
The cooling load in air-conditioned rooms is calculated according
to the respective national standards. In Germany, for example,
the national standard is VDI 2078 (VDI cooling load regulations).
This guideline contains two calculation methods (the “short
method” and the computer method) as well as additional
information for calculating the cooling load of air-conditioned
rooms and buildings. The computer method does not serve to
improve accuracy for standard conditions. However, it can be
used to expand the range of applications to include almost any
boundary conditions (variable blind systems, room temperature,
etc.). In actual use, this method is too complex for standard
conditions.
In the case of simple types of buildings such as offices, doctors'
practices, shops or private residences, it is practical to make a
rough calculation with values based on past experience or using
the so-called HEA short method from the German “Fachverband
für Energie-Marketing und - Anwendung e.V.” (English: Trade
Association for Energy Marketing and Use).
NOTE
Visit www.dimplex.de to use our online planner to calculate the
approximate cooling load.
= 0.03 kW/m
2
Low-energy house
= 0.05 kW/m
2
Acc. to thermal insulation ordinance 95 or
the EnEV (Energy Saving Regulation) 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
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