Nibe S735 - Heat Pump Function

This exhaust air heat pump uses the heat that is in the
building’s ventilation air and the outdoor air to heat the
home. The conversion of the air's energy to domestic heating
is performed in three different circuits. Heating energy is
retrieved from the outgoing air (1) from the home and
transported to the heat pump. The heat pump increases the
recovered heat’s low temperature to a high temperature in
the refrigerant circuit (2). The heat is distributed around the
house in the heating medium circuit (3).
-15 ºC
-15 ºC
-5 ºC
100 ºC
55 ºC 45 ºC
22 ºC
Heating medium
Refrigerant
Evaporator
Condenser
Compressor
1
2
3
Expansion valve
Exhaust air
Extract air
Outdoor
air
A
B
C
D
F
E
G
I H
The temperatures are only examples and may vary between
different installations and time of year.
Ventilation air
The hot air is transferred from the rooms to the heat pump
via the house ventilation system. Outdoor air is only used if
necessary.
A
The fan then routes the air to the heat pump’s evaporator.
Here, the air releases the heating energy and the air's tem-
perature drops significantly. The cold air is then blown out
of the house.
B
Refrigerant circuit
A liquid, a refrigerant, circulates in a closed system in the
heat pump which also passes the evaporator. The refrigerant
has a very low boiling point. In the evaporator the refrigerant
receives the heat energy from the ventilation air and starts
to boil.
C
The gas that is produced during boiling is routed into an
electrically powered compressor. When the gas is com-
pressed, the pressure increases and the gas’s temperature
increases considerably, from approx. -5°C to approx. 100°C.
D
From the compressor, the gas is forced into a heat exchanger,
condenser, where it releases heat energy to the heat pump’s
heating section, whereupon the gas is cooled and condenses
to liquid form again.
E
As the pressure is still high, the refrigerant can pass an ex-
pansion valve, where the pressure drops so that the refriger-
ant returns to its original temperature. The refrigerant has
now completed a full cycle. It is routed to the evaporator
again and the process is repeated.
F
Heat medium circuit
The heat energy that the refrigerant produces in the condens-
er is retrieved by the climate system's water, heating medium,
which is heated to 55 °C (supply temperature).
G
The heating medium circulates in a closed system and
transports the heated water's heat energy to the heat pump's
integrated hot water heater and the radiators/heating coils
of the house.
H
The heat pump’s integrated water heater is in the heating
section. The heating medium heats the hot water.
I
NIBE S735Chapter 2 | Heat pump function6
Heat pump function