49
Conditions for passive cooling
Passive cooling ON Passive cooling OFF
All of the following conditions must be met:
■
Outdoor air temperature (heat exchanger air intake) is
< extract air temperature minus 4 K
■
Outdoor air temperature (heat exchanger air intake) is
> "Min. supply air temperature for bypass 7D0F"
plus 0.5 K
■
Extract air temperature > "Set extract air tempera-
ture 7D08" plus 1 K
One of the following conditions must be met:
■
Outdoor air temperature (heat exchanger air intake) is
≥ extract air temperature minus 0.5 K
■
Outdoor air temperature (heat exchanger air intake) is
≤ "Min. supply air temperature for bypass 7D0F"
plus 0.5 K
■
Extract air temperature ≤ "Set extract air tempera-
ture 7D08"
Passive cooling will not start if one of the following
conditions is met (bypass not active):
■
A sensor or fan fault has occurred.
■
Frost protection is active.
■
The electric preheating coil has been on in the last
10 min.
Frost protection
Defrost functions
The degree of icing up of the heat exchanger is moni-
tored. The selected defrost function is activated
according to the degree of ice formation: See following
table.
The determine the degree of ice formation the two fol-
lowing variables are observed and additional condi-
tions are taken into account, e.g. the installation posi-
tion of the ventilation unit ("Installation position
7D2F").
■
Fan speeds:
The pressure differential in the heat exchanger rises
with increasing ice formation. The fan speeds are
automatically increased to maintain a constant air
flow rate. From a certain speed onwards it is
assumed that the heat exchanger is iced up.
■
Supply air temperature:
The heat exchanger transfers less heat from the
extract air to the outdoor air due to ice formation.
The supply air temperature drops. From a certain
supply air temperature threshold onwards it is
assumed that the heat exchanger is iced up.
Monitoring of ice formation is active under the following
conditions:
■
The outdoor air temperature is below 2 °C.
■
No defrost function was active during the last 15 min.
■
The fans are switched on.
■
None of the temperature sensors in the ventilation
unit is faulty.
The defrost function is selected with the parameters
"Enable preheater bank electric 7D01" and "Strat-
egy, passive frost protection 7D2C".
Function description
Mechanical ventilation with Vitovent 200-C (cont.)
5816558
Functions
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