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17
General terms
Annual power input factor
The annual power input factor indicates the power
input (e.g. electrical energy) required in order to
achieve a certain benefit (e.g. heating energy). The
annual power input factor includes the energy
required for auxiliary drives. Calculation of the
annual power input factor is undertaken according
to VDI – Directive 4650.
Bivalent mode
The heat pump provides the entire heating energy
down to a predetermined outdoor temperature
(e.g. 0°C). If the temperature drops below this
value, the heat pump switches off and the secon-
dary heating appliance takes over the heating, e.g.
a heating boiler.
Coefficient of performance
The current ratio of thermal output produced by the
heat pump to the consumed electrical power is
referred to as the coefficient of performance, as
measured under standardised boundary conditions
according to EN 255 / EN 14511. A coefficient of
performance of 4 means that a usable thermal
output amounting to 4-times the electrical power
consumption is available.
Compressor (condenser)
Unit designed for the mechanical conveyance and
compression of gasses. Compression serves to
significantly increase the pressure and tempera-
ture of the medium.
Condenser
Heat exchanger on a refrigerant plant which lique-
fies a working medium in order to transmit heat to
its environment (e.g. the heating system).
Defrost
At outdoor temperatures below 5°C it is possible
that ice may form on the evaporators of air/water
heat pumps. The removal of this ice is referred to
as defrosting and is undertaken by supplying heat,
either regularly or as requirements dictate. Air/
water heat pumps with circuit reversal are distin-
guished by their requirements-based, quick and
energy-efficient defrosting system.
Energy supply company switching
Certain energy supply companies offer special tar-
iffs for the operation of heat pumps.
Evaporator
Heat exchanger on a refrigerant plant which uses
the evaporation of a working medium in order to
extract heat from its environment at low tempera-
tures (e.g. the outdoor air).
Expansion valve
Heat pump component for lowering the condensing
pressure on the vapour tension. In addition, the
expansion valve regulates the quantity of injected
refrigerant in relation to the evaporator load.
Heat carrier
Liquid or gas medium (e.g. water, brine or air), in
which heat is transported.
Heat pump system
A heat pump system consists of a heat pump and
a heat source system. For brine and water/water
heat pumps, the heat source system must be
made available separately.
Heat requirement assessment
A precise dimensioning of the system must be car-
ried out for heat pump systems in order to maxi-
mise efficiency. Calculation of the heat require-
ment is undertaken according to national
standards. However, approximate requirements
can be determined based on the W/m² tables mul-
tiplied by living space to be heated. The result of
this is the overall heat requirement, which includes
the transmission heat requirement and the infiltra-
tion heat loss.
Heat source
Medium from which the heat pump derives heat, in
other words, soil, air and water.
Heating output
Flow of heat emitted from the liquefier to the envi-
ronment. The heating output is the sum of the elec-
trical power consumed by the condenser and the
heat flux obtained from the environment.
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