Outside Air Damper Fan Coils ("Economizer", Fnc10, Fnc12) - Siemens Desigo RXB Technical Manual

Enabling the function
Control sequence,
damper actuator
Siemens
Building Technologies
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.
Y [%]
100
min
0
SpFr SpEmc SpC
RXB (KNX) application library
Control sequences
Y
min
TO
SpC
SpEcm Economizer setpoint
SpFr
TO [°C]
FNC Description of functions for FC-10, FC-11, FC-12
Position of damper actuator
Min. damper position
Outside air temperature
Cooling setpoint
= Outdoor temp. min. damper position
Frost protection limit value
CM110385en_05
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28 Feb 2009