Figure 2-35 Control behaviour for the H VAV controller mode when the maximum VAV output on heating
demand setting is applied.
2.7 Forced ventilation
Forced ventilation is a control function that is used to improve the air quality in a room through increased
airflow. This is achieved by fully opening the damper that regulates the airflow into the room, which
provides an additional amount of fresh air and decreases the CO
2
level. The forced ventilation function can
also be used to boost the heating or cooling distribution when the heating, cooling, or VAV output signal has
reached its maximum.
The forced ventilation function can be used in all controller modes, and is enabled by applying the
Forced
ventilation active
or
Forced ventilation active at max output
configuration settings, that is, changing them from
their
Off
values.
The forced ventilation function is activated when the controller changes to bypass state and any of the
conditions specified by the
Forced ventilation active
or
Forced ventilation active at max output
settings are
fulfilled. See section
for information about bypass state.
When the forced ventilation function is active, a digital controller output that is configured with the
Forced
ventilation
value is active, and the analog VAV output signal is set to its maximum for the controller modes
that include a VAV sequence. Optionally, for the C VAV and H C VAV controller
modes, the cooling output signal can be configured to also be set to its maximum when the forced
ventilation is active.
The forced ventilation configuration settings in Application tool are shown in
Figure 2-36 Forced ventilation configuration settings in Application tool.
Heating signal
VAV signal
Output
Max: 100%
Heating
setpoint
Cooling
setpoint
Min: 0%
Deadband
Room temperature
100%
100%
0%
0%
Cooling demand
Heating demand
Max VAV at
heating demand: 50%
Regio
Ardo
manual, Rev. D
41