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Siemens Standard application AHU CE1P3977en_02
Building Technologies Functions 01.02.2010
5.2.6 Night cooling (Free Cooling)
Night cooling (free cooling) is enabled.
Main Index > Configuration > Configuration 2 > Night cooling <> No
Night cooling cools down a building at night using cool outside air without auxiliary
energy for high daytime temperatures.
• Night cooling is switched on in the following cases:
– Outside air temperature is greater than the lower level: Out tmp > Min outs
tmp
and
– Outside air temperature is less than the difference from room temperature and
switch-on differential: Out tmp < Room tmp - Delta
and
– Room temperature is greater than the sum of the room setpoint and hystere-
sis: Room tmp > Room tmp setpoint + hysteresis.
• Night cooling is switched off in the following cases:
– Timer Min run time = 0
and
– Plant switches on.
or
– Outside air temperature is less than the difference from room temperature and
switch-off differential: Out tmp > Room tmp – 1 or
– Room temperature is less than or equal to room setpoint: Room tmp <= Room
tmp setpoint
The function is disabled for faulty outside air or room temperature.
Main Index > Unit > Operating mode > Night cooling
Parameter Range Function
Room tmp setpoint
-64.0…64.0 [°C]
Room setpoint for night cooling. Setpoint applies to return air
for night cooling with a return air sensor.
Hysteresis 0.0…64.0 [°C] Hysteresis for switch on.
Delta 1.0…64.0 [°C] Minimum difference between room and outside air tempera-
ture.
Min outs tmp -64.0…64.0 [°C] Minimum outside air temperature to activate night cooling.
Min run time 0…999 [min] Minimum runtime after a start.
5.2.7 Temperature difference start
Plant start by temperature difference is enabled:
Main Index > Configuration > Configuration 2 > Tmp start <> No
Plant night start based on temperature difference prevents the building from cool-
ing down or heating up too much. It is controlled to a separate setpoint for heating
and cooling.
The heating and or cooling start can be enabled separately:
Main Index > Configuration > Configuration 2 > Tmp start
The function can be implemented using a return air sensor if no room sensor is
available.
Prerequisite
Function
Note
Parameter
Prerequisite
Function
Basis Document Siemens Climatix Control System
BDCX.100820.01GB
Page 44
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