User Manual

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Siemens Central apartment unit QAX910 CE1N2707en
Building Technologies 06.01.2009
Specific functions for heating plants
The central apartment unit generates heat demand signals based on the collected
heat requests and forwards the signals to the controller for heat generation.
The heat demand signals can be delivered via the universal relay output (switch-
ing) or the DC 0…10 V output (modulating) of an RRV912 heating circuit controller
or RRV934 multi-controller.
The flow temperature is controlled via the RRV934 multi-controller. It is regulated
with the help of the heat demand signals. Also, minimum and maximum limitation
of the flow temperature can be provided. If the temperature request is invalid, flow
regulation will be deactivated and the controlling elements closed (no output). The
central apartment unit supports 2 room groups (e.g. floor heating and radiators)
which can be controlled independently of one another.
Return temperature limitation is adjustable, enabling it to be kept at a high or low
level. It is thus possible to prevent too hot water from returning to the heat source,
for example. Return temperature limitation is given priority over flow temperature
limitation. It acts on the mixing valve of the room group.
If a room unit and 1 or 2 room temperature sensors are assigned to a room, the
central apartment unit calculates the mean value and uses it for room temperature
control.
Several heating circuits connected to an RRV912 / RRV918 heating circuit control-
ler can be combined to one room and operated in parallel. In that case, the first
channel ensures room temperature control and, at the same time, controls the
other assigned channels.
Up to 6 SSA955 radiator control actuators can be combined to one room and oper-
ated in parallel.
In that case, the radiator control actuator connected first (lead controller) ensures
actual room control plus wireless control of the other assigned radiator control ac-
tuators (lag controllers).
Several heating circuits connected to a common heat distributor can be jointly con-
trolled as one zone. The zone valve (3-position) is controlled based on the room
temperature acquired by the room unit installed in the reference room and / or the
room temperature sensor.
The central apartment unit ensures release of the room group pumps. The pumps
can be connected either to the internal relay output or a relay output of one of the
RRV912 / RRV918 heating circuit controllers or the RRV934 multi-controller.
The QAX910 can trigger the antilime function at regular intervals, aimed at prevent-
ing valve plugs and pump impellers from seizing during longer off periods. The
function ensures that the valve actuators will travel to the fully open and then to the
fully closed position and that the pumps will be activated for short periods of time
(valve kick). Both frequency and time of day at which the function is performed can
be selected.
The antilime function acts either locally or on plant components connected to the
RRV912 / RRV918 heating circuit controller and the wireless SSA955 radiator con-
trol actuators.
Heat request
Flow temperature
control / limitation
Return temperature
limitation
Room unit / room
temperature sensor
Parallel operation
of heating circuit
controllers
Parallel operation
of radiator control
actuators
Zone control
Room group pumps
Antilime function