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Installation instructions
17.4 Free cooling function
There can be climatic conditions during the year that
make it impractical to recover heat from extracted
air for treating fresh air from outside.
For example, in mid-season, the outdoor air temperature
can be lower than the indoor air temperature due to solar
and internal factors, and this tends to occur when the
indoor temperature is between 22 and 26°C so there is
more of a need for cooling than for heating. In this case it
is advisable to use free-cooling, i.e. fresh air from outdoors
to cool for free, bypassing the heat recovery unit.
Conversely, it is possible to use fresh air for heating
during a change in season, in which case the process is
known as free-heating.
The units are equipped with a bypass damper system
that totally disables use of the recovery heat exchanger
to permit free-cooling (or free-heating).
The system is controlled on the basis of a logic subject to
the feedback of the integrated temperature probes.
Fig. 69 Free cooling graph
35
30
26
25
T1 [C°]
t
20
15
10
10
42
FREE-HEATING
MODE
heating
WINTER
RECOVERY
15
Lindab reserves the right to make changes without prior notice
li n d a b | w e s i m p l i fy c o n s t r u c t ion
The logic is as follows:
The indoor air temperature setpoints of the air conditioning
system in winter and summer are defined in order to
maintain conditions of comfort
t heating
normally
normally t cooling =
t cooling
(temperatures can be modified by the installer according to
the actual settings of the plant)
The following are also defined:
t i = indoor air temperature (return air)
EAT = External Air Temperature
FREE-COOLING CONDITION
EAT > t heating and simultaneously t i >EAT
FREE-HEATING CONDITION
EAT < t cooling and simultaneously t i <EAT
SUMMER
RECOVERY
FREE-COOLING
20
25
T3 [C°]
2022-01-28
RHR-CF
:
t heating
=
20°C
26°C
t
cooling
MODE
30
35
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