Passive Cooling - Viessmann VITOTRONIC 200 Service Instructions Manual

Function description
Mechanical ventilation with Vitovent...
If an enthalpy heat exchanger is installed in the ventila-
tion unit, a part of the humidity is also transferred to
the supply air stream in addition to the thermal energy.
This contributes to a healthy ambience.
During heat recovery and humidity control the bypass
is not active.
For passive cooling the bypass is switched on: See
chapter "Passive cooling".
Balancing of the supply air and extract air flow
rates
Due to the conditions in the building, an unwanted flow
rate differential (disbalance) may occur between the
supply air and extract air side, e.g. through different
lengths of pipework for outdoor/supply air and extract/
exhaust air.
Note
To determine the flow rate differential, the captured
flow rates of all supply air apertures must be added
together and compared to the total flow rates of all
extract air apertures.

Passive cooling

With passive cooling, the ventilation unit uses the out-
door air for central cooling.
Note
Subject to the temperature conditions, only low cooling
capacities are available during passive cooling.
With passive cooling, the outdoor air is not routed via
the heat exchanger, but instead via the bypass directly
into the rooms. The bypass opens and closes automat-
ically, depending on the following conditions:
Conditions for passive cooling
Passive cooling ON
All of the following conditions must be met:
Outdoor air temperature (heat exchanger air inlet) >
■
7 °C
Extract air temperature > "Set room temperature
■
C108" plus 2 K
Extract air temperature > outdoor air temperature
■
Passive cooling will not start if one of the following
conditions is met (bypass not 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 C108" is set min. 4 K
higher than "Standard room temperature 2000".
66
(cont.)
Ventilation unit installation and service instruc-
tions
Flow rate differentials > 10 % must be balanced out as
follows:
Vitovent 200-W:
The air flow rates for supply air and extract air can
■
be set separately for each ventilation level, e.g.
"Standard ventilation C10B" for the supply air
stream and "Standard ventilation, second fan
duct C18B" for the extract air stream.
Vitovent 300-C/300-W:
■ To enable the balancing of flow rate differences
between the supply and extract air sides, "Imbal-
ance permitted C1A2" must be set to "1".
The increasing or decreasing of the supply air
stream in comparison to the extract air stream can
be set with "Specified imbalance C1A3".
Enabling required
Parameter
"Bypass mode C1A0"
Passive cooling OFF
One of the following conditions must be met:
Outdoor air temperature (heat exchanger air intake)
■
6.5 °C
Extract air temperature
■
C108" minus 0.5 K
Extract air temperature
■
nus 0.5 K
Setting
"0"
"Set room temperature
≤
outdoor air temperature mi-
≤
≤