Sauter flexotron®800
ventilation
Functional description
P100012082
41
5.1.6
Free cooling
This function is used during the summer to cool the building night-time using cool
outdoor air, thereby reducing the need for cooling during the day and saving energy.
Free cooling requires an outdoor sensor (or an inlet temperature sensor) and either a
room sensor
or
an extract air sensor. The outdoor sensor can be placed in the fresh air
inlet duct.
Free cooling is only activated when all the start conditions are fulfilled.
Start conditions:
Less than four days have passed since the unit was last in running mode.
The outdoor temperature during the previous running period exceeded a set
limit (22°C).
It is between 00:00 and 07:00:00 in the day (settable).
The timer outputs for "normal speed", "Extended running, Normal" and
"External switch" are Off.
A timer channel will be On sometime during the recently started 24 hours.
If the outdoor sensor is located in the fresh air inlet duct and/or an extract air sensor is
selected and ALL the start conditions are fulfilled, free cooling is activated and will run
for 3 minutes to ensure that the temperature measurement when using an extract air
sensor reflects the corresponding room temperature and that the outdoor temperature
sensor senses the outdoor temperature even if it is placed in the fresh air inlet duct. If
the outdoor sensor is not located in the fresh air inlet duct and a room sensor is
selected, the unit will not start free cooling as long as all the temperatures are not within
the start and stop temperature intervals.
After three minutes, the stop conditions will be controlled.
Stop conditions:
Outdoor temp above the set max. value (18°C) or below the set min. value
(condensation risk, 10°C).
The room temp/extract air temp. is below the set stop value (18°C).
The timer outputs for "normal speed", "Extended running, Normal" or "External
switch" are On.
It is past 07:00:00 in the day.
If any stop condition is fulfilled after three minutes, the unit will stop again. Otherwise,
operation will continue until a stop condition is fulfilled.
When free cooling is active, the fans run at normal speed or the set value for
pressure/flow control and the digital output "Free cooling operation" is active. The
outputs "Y1-Heating", "Y2-Heat exchanger" and "Y3-Cooling" are shut down. After free
cooling has been active, the heating output is blocked for 60 minutes (configurable
time).
In- and outputs
AI
Outdoor temperature sensor
or
Intake
temperature
AI
Room sensor
or
Extract air sensor
DO
Free cooling operation