Installation manual

16
1.3.4.5
Heat pump output
The heat output should be dimensioned for a limit temperature
below -10 °C. This yields a heat pump output of 75 % to 95 %
measured as a percentage of the total heat consumption based
on the lowest external temperature.
Heat source variables
When using earth energy as the heat source (ground source),
the ground heat collector or borehole heat exchanger should be
dimensioned on the basis of the total heat consumption to ensure
that any formation of ice thaws in the spring. When dimensioning
the well for water-to-water heat pumps, no further requirements
for mono energy operation need to be taken into consideration
apart from standard design criteria.
1.3.4.5 Air-to-water heat pump (bivalent operation)
When a system is operated as a bivalent-parallel system
(existing older building), a second heat generator (oil or gas
boiler) assists the heat pump from the bivalence point of < 4 °C.
It is often useful to select a smaller sized heat pump since the
heat pump's percentage of annual heat output fluctuates very
little. A prerequisite is that long-term operation of a bivalent
system is planned.
NOTE
Experience has shown that, in the case of bivalent systems used in
modernisation projects, the existing oil or gas boiler will be taken out of
service after a few years, for a variety of reasons. Therefore,
dimensioning should always be carried out analogue to the mono energy
system (bivalence point is approx. -5 °C). At the same time, the buffer
tank should also be integrated into the heat flow.
1.3.4.6 Water-to-water and brine-to-water heat pumps (bivalent operation)
The same interrelationships generally apply for bivalent
operation of water-to-water and brine-to-water heat pumps as for
air-to-water heat pumps. However, other dimensioning factors
must be considered depending on the layout of the heat source
system.
Ask our heat pump system specialists if you have any questions
on this topic.
1.3.4.7 Drying-out of buildings
When a house is being built, large quantities of water are
normally used for mortar, rendering, plaster and wall paper,
which only evaporates very slowly from the building. In addition,
rain can decisively increase the humidity in the building's
structure. This increased humidity in the entire structure causes
an increase in the heat consumption of the house during the first
two heating periods.
For this reason, buildings should be dried out using specially
designed dehumidifiers. Particularly if brine-to-water heat pumps
are implemented, we recommend installing an additional heating
element to compensate for the increased heat consumption if the
heat outputs of the heat pump have been marginally calculated
and the respective building is to be dried out in autumn or in the
winter. In the case of brine-to-water heat pumps, this heating
element should then only be activated during the first heating
period on the basis of the brine flow temperature (approx. 0 °C)
or on the basis of the limit temperature (0 °C to 5 °C).
NOTE
In the case of brine-to-water heat pumps, the increased compressor
runtimes could cause the heat source to supercool in turn causing the
heat pump to automatically switch off.