Viessmann VITOTRONIC 200 Service Instructions Manual page 62

Function description
Mechanical ventilation with Vitovent 200-C/300-F
Without electric preheating coil
Defrost func- Description
tion
Shutdown of If the heat exchanger is iced-up, both fans are switched off.
fans
Defrosting via If the heat exchanger is iced-up, the bypass opens and the cool outdoor
bypass air is routed past the heat exchanger. The extract air additionally heats
the heat exchanger. This causes the ice to melt and drain off as con-
densate.
Note
Condensate may form in the cooling supply air pipes.
In the case of persistent ice formation both fans are switched off.
Defrosting by If the heat exchanger is iced-up, the supply air fan is switched off. The
means of disba- extract air heats the heat exchanger. This causes the ice to melt and
lance drain off as condensate.
In the case of persistent ice formation both fans are switched off.
With electric preheating coil
Defrost func- Description
tion
Defrosting via If the heat exchanger is iced-up the electric preheating coil is switched
bypass on and the bypass is activated. The ice melts and drains off as conden-
sate.
If the output of the preheating coil is not enough, the supply air flow rate
is additionally reduced in stages.
Frost protection comfort function
With the frost protection comfort function, ice formation
on the heat exchanger is largely prevented. If "Enable
preheater bank electric 7D01" is set to "2", this func-
tion is always active.
The electric preheating coil is switched on if the differ-
ential between supply air and extract air temperature
exceeds 4.5 K. This protects the heat exchanger of the
ventilation unit against icing up.
If the output of the electric preheating coil is no longer
adequate due to low outside temperatures, the supply
air flow rate is incrementally reduced.
With frost protection comfort function the bypass is not
active. Heat recovery remains switched on.
The frost protection comfort function prevents uncom-
fortable supply air temperatures, however, the energy
demand during extreme weather conditions is slightly
higher than when defrosting via bypass.
62
(cont.)
Starting the fans up again
If the temperature conditions during an active defrost
or frost protection function cause the fans to be shut
down, the fans can not start back up until the next start
time is reached.
Requirement: The temperature conditions for start up
are met.
The start times are set with "Starting block, ventila-
tion periods part 1 7D5E" and "Starting block, ven-
tilation periods part 2 7D5F".
Setting
"7D01" "7D2C"
"0" "0"
"0" "1"
"0" "2"
Setting
"7D01" "7D2C"
"1"
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