183
English
• 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 midseason, 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.
Energy Plus units are equipped with a bypass
damper that disables use of the recovery
exchanger to permit free-cooling (or free-hea-
ting).
The damper is controlled on the basis of a
logic subject to the feedback of the integrated
temperature probes.
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 t
heating
= 20°C
t
cooling
normally t
cooling
= 26°C
The following are also defined:
t
i
= internal 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
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