Technical data

1.3
4
The values specified by this method are calculated on the basis
of the VDI 2078 cooling load regulations. The calculation is
based on a room temperature of 27 °C, an external temperature
of 32 °C and continuous operation of the cooler.
NOTE
The cooling requirements of the building are calculated by adding up the
cooling loads of the individual rooms. Depending on the type of building,
a simultaneity factor can be used under certain circumstances because
rooms on the east and west sides do not have to dissipate solar heat
loads simultaneously.
1.3 Checking the Operating Limits
1.3.1 Maximum Heat Output of the Heat Pump
If the heat consumption of the building is higher than its cooling
requirements, the heat pump should be configured for heating
operation. Then it must be checked if the cooling output of the
heat pump system is higher than the cooling requirement of the
building.
Chap. 1.3.3 on p. 6 shows possibilities for reducing the cooling
requirements of the building calculated for each room.
If the heat consumption of the building is lower than its cooling
requirements, the heat pump can also be configured for cooling
requirements.
1.3.1.1 Monovalent operation
In this mode of operation, the heat pump covers the heat
consumption of the building throughout the whole year - 100% -
by itself. Brine-to-water heat pumps are normally operated in
monovalent mode. Refer to the Device Information of the
respective device for the actual heat outputs at each respective
flow temperature and minimum heat source temperatures.
Table 1.2: Example of calculating the heat output
1.3.1.2 Mono Energy Operation
Air-to-water heat pumps are primarily operated in mono energy
systems. The heat pump should cover at least 95% of the heat
consumption. At lower temperatures and high heat consumption,
the electrically operated immersion heater is switched on
automatically.
In the case of mono energy systems, dimensioning of the heat
pump output has a particularly strong influence on the level of the
investment and the annual heating costs.
The higher the annual energy demand for heating met by the
heat pump, the greater the investment costs and the lower the
annual operating costs.
For example:
Calculating the necessary heat requirements to dimension a heat
pump for heating and cooling with central hot water preparation
for 5 persons.
 Heat consumption of
building to be heated 11 kW
 Additional heat requirement
for hot water preparation 1 kW
Heat requirement + hot water preparation
= 11 kW + 1 kW 12 kW
Dimensioning of a reversible air-to-water heat
pump with mono energy operating mode:
The design is to be determined for the dimensioning of the heat
pump. The design is made up, on the one hand, of the required
heat consumption and, on the other hand, of the lowest possible
external temperature (coldest day). This means that the heat
pump system must cover the max. possible heat consumption
(12 kW) at the min. possible external temperature (coldest day).
The determined design is to be entered in the diagram with the
various characteristic curves of the possible air-to-water heat
pumps (see Fig. 1.1 on p. 5 and Fig. 1.2 on p. 5) as intersection
of heat consumption and minimum external temperature (section
).
The further design is done via the external temperature-
dependent heat consumption of the building. The latter is drawn
in the diagram in simplified fashion as a straight line between the
design and point 20 °C/0 kW. When using this procedure, it is
assumed that no more heat consumption (straight line ) exists
above an external temperature of 20 °C (air intake temperature
of the heat pump).
The intersection of the straight lines (design to the end point at 20
°C/0 kW) with the respective heating output curves determines
the theoretical bivalence points when using the individual heat
pumps (section ). The bivalence point enables a statement to
be made about up to which external temperature the heat pump
can cover the entire heat consumption alone (above the
bivalence point) and from which time the heating element must
be theoretically activated (below the bivalence point). The
bivalence point is often lower in practice because of actual usage
(e.g. unheated bedrooms, kitchen or hobby room with reduced
temperature).
NOTE
The remaining output of the heating element still required in the design
may not exceed a max. value of 6 kW.
Brine-to-water
heat pump
Water-to-water
heat pump
Maximum
flow temperature
35°C 35°C
Minimum heat
source
temperature
Brine 0 °C Ground water 10 °C
Operating point for
determination of
the heat output
B0 / W35 W10 / W35