Vitovent 200-C: Frost Protection - Viessmann VITOTRONIC 200 Service Instructions Manual

Mechanical ventilation with Vitovent 200-C/300-F
Vitovent 300-F: Conditions for passive cooling
Note
Ventilation level is set while the bypass opens or
1
closes.
Passive cooling ON
All of the following conditions must be met:
Outdoor air temperature (heat exchanger air intake) <
■
extract air temperature minus 4 K
Supply air temperature > "Min. supply air tempera-
■
ture for bypass 7D0F" minus 1.5 K
Outdoor air temperature (heat exchanger air intake) >
■
"Min. supply air temperature for bypass 7D0F"
plus 1.5 K
Extract air temperature > "Set room temperature
■
7D08" plus 1 K
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.
■ If central heating is switched on:
Central heating via one heating circuit that also sup-
plies the ventilated rooms ("Heating circuit for
blocking bypass damper 7D21").
This prevents heat supplied via the heating circuits
being routed outside via the bypass.
■ "Set room temperature 7D08" is set min. 4 K
higher than "Standard room temperature 2000".

Vitovent 200-C: 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.
(cont.)
Passive cooling OFF
One of the following conditions must be met:
Outdoor air temperature (heat exchanger air intake)
■
extract air temperature minus 3 K
Supply air temperature
■ ≤
ture for bypass 7D0F" minus 1.5 K
Outdoor air temperature (heat exchanger air intake)
■
"Min. supply air temperature for bypass 7D0F"
plus 1.5 K
Extract air temperature
■
7D08"
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
"Min. supply air tempera-
"Set room temperature
≤
≥
≤
61