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Siemens
RXB (KNX) application library
FNC Description of functions for FC-10, FC-11, FC-12 CM110385en_05
Building Technologies
Control sequences
28 Feb 2009
The following conditions must be fulfilled:
– The room controller must be in
Comfort
mode
– The radiator must not be disabled (e.g. by
application mode
= COOL).
8.6
Outside air damper fan coils ("Economizer",
FNC10, FNC12)
The outside air damper mainly serves to provide the room with fresh outside air. In
addition, the outside air can be used to cool the room.
The outside air damper is
always
operated in
Comfort
and
Precomfort
modes.
In
Economy
mode,
it is operated only in conjunction with the following special functions
(see page 128 ff. for a description):
Pre-Cool, Free Cool, Night Purge and Fan-Only.
The damper is controlled through a stroke model calculated from the runtime of the
actuator.
The Economizer setpoint
Outside air temp. min. damper pos.
defines at which outside
temperature the
outside air damper is opened to an adjustable minimum position.
This minimum position ensures a constant air supply below the outside air temperature.
The
Outside air temp. min. damper pos.
setpoint should be selected to ensure that
there is at least a difference of 4 K between this value and the cooling setpoint and that,
at the same time, no draught is caused by the inflow of cold outside air.
The Economizer setpoint should not be much lower than the
Comfort
heating setpoint,
otherwise too much cool air would come into the room during the heating sequence.
Above the
Outside air temp. min. damper pos.
setpoint, the
damper is opened
beyond the minimum position
if:
– the outside temperature is below the room temperature and
– either the room controller is in
Comfort
or
Precomfort
room operating mode
or
one of the special functions "Pre-Cool", "Free Cool", "Night Purge" or "Fan-Only" is
active
The
damper is fully closed
if:
– the outdoor temperature drops below the
frost protection
limit (see page 33)
– the safty thermostat for the outdoor temperature is activated (see page 126)
– the special function "Emergency Heat" is active in
Economy
mode
– the outside air temperature is above the room temperature.
1
038
5D
18
Y [%]
100
min
0
SpFr SpEmc SpC
TO [°C]
Y
Position of damper actuator
min
Min. damper position
TO
Outside air temperature
SpC Cooling
setpoint
SpEcm Economizer setpoint
= Outdoor temp. min. damper position
SpFr
Frost protection
limit value
Enabling the function
Control sequence,
damper actuator
