Operating Instructions

Table Of Contents
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Siemens RXB (KNX) application library RXB Description of functions for FC-10, FC-11, FC-12, FC-13 CM110385en_08
Building Technologies General and central functions 2013-06-17
11.14 Free cooling (Freecool, 10)
This function is used to precool rooms to the Comfort cooling setpoint, in readiness for
normal occupancy. It uses both fan and cooling coil.
This function is meaningful only if low-tariff energy is available.
During occupancy (Comfort / Precomfort) normal mode applies.
3-step fan DC 0...10 V fan
100
TR
10385D28
0
Y [%]
SpH
Cmf
SpC
Cmf
100
TR
10788z09
0
Y [%]
SpH
Cmf
SpC
Cmf
Fan
Cooling coil
The function can be disabled in the room controller by means of P135 or the ETS tool, ,
together with Pre-cooling, see central functions, page 139.
The function must be enabled via the building automation and control system
(communication object Application mode, see page 145).
The function is disabled via the building automation and control system.
11.15 Alarm
Alarms differ in S-mode and LTE mode.
RXB controllers support different alarms:
Room temperature frost If the room temperature or the return temperature in a fan-coil
application drops below the fixed frost protection limit (5 °C or
adjustable for outside air applications), an alarm is generated.
Outside air temperature frost In applications with outside air damper, a safety thermostat in the
outside air duct can be connected to the digital input.
Overheating alarm If the digital input of an RXB22.... controller is used as an overheating
alarm (see page 96), the information is transmitted in this alarm
message.
Supply air sensor error,
Room sensor error
Sensor fault or short circuit.
PPS2 fault If the PPS2 communication between a controller and the room unit is
interrupted, or the room unit has an internal fault, the information is
transmitted in this alarm message.
No air flow If a digital input of an RXB39.1 controller is used for air flow monitoring
(see section 11.2), an alarm is created when the sensor trips.
Enabling the function
Initiating the function
Terminating the function