User Manual

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Siemens HVAC central apartment unit with consumption data acquisition QAX903 CE1N2741en
Building Technologies 2016-01-30
The Economy room temperature setpoint to heat all rooms is increased dependent
on the composite outside temperature. The transitions are adjustable and help
prevent peak loads during changeover, for example, from Economy to Precomfort
or Comfort.
T
he minimum flow temperature setpoint is increased depending on the composite
outside air temperature, ensuring a minimum flow temperature in uncontrolled
rooms.
T
he central apartment unit triggers summer operation. Changeover can occur
manually, by date, as per attenuated outside air temperature, via a digital input, or
through active changeover to cooling mode.
The heating circuit valves connected to an RRV912 / RRV918 heating circuit con-
troller have a position of 0% or 100% and the SSA955 radiator control actuators
are driven to the preselected valve positions.
S
pecific functions for floor cooling
4 cooling setpoints can be preset for each room. A flow refrigeration request is
calculated per room group for primary processing. The room group controller
RRV934 controls the flow temperature depending on composite outside air tem-
perature and individually adjustable cooling curve.
QAX903 can override room controllers RRV912, RRV918 and SSA955 in cooling
mode.
A
condensation monitor (QXA2000, AQX2000) monitors the dew point on the flow
pipe.
The condensation monitor acts simultaneously on both room groups (1 dew point
monitor per QAX903).
F
loor cooling is enabled:
− Manually on the QAX903.
− Via external switch (digital).
− Via programmable date.
− Via composite outside air temperature.
− Via KNX S-mode.
Specific functions for ventilation and air conditioning units
The QAX903 can control a ventilation plant with up to 3 ventilation stages via multi-
controller RRV934. The stages can be controlled manually, via a weekly scheduler
or using an air quality or humidity sensor. Ventilation may be influenced by ab-
sences, holiday functions or an open window.
The following operating and control functions are available:
− The apartment timer activates apartment operating mode "Comfort" for an
adjustable period.
− Rapid ventilation activates the maximum ventilation stage for a predefined
period.
− Cooler outside air flows through the heat recovery bypass in summer mode as
part of active night cooling.
− Count operating hours to generate a maintenance message.
− Enable kitchen fume hood via an open window to ensure replacement air.
− Display active chimney ventilation mode (external plant).
Outside air
temperature-controlled
night setback
Minimum
flow setpoint
Summer operation
Room control
Dew point monitoring
Floor cooling enable
Ventilation