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Electric heater
Changeover between heating and cooling operation
!
Valves
Fan operation
4/10
Siemens Building Technologies
HVAC Products
There is also an inbuilt relay for direct connection of an electric heater.
The control of the heater depends on the control deviation (pulse duration modulated)
The P-band of the electric heater is:
Control sequence 2-pipe fan coil c/o (changeover) cooling = 2 K (S5=on)
−
Control sequence 2-pipe fan coil c/o (changeover) cooling = 4 K (S5=off)
−
Control sequence 2-pipe fan coil c/o (changeover) heating = 0.4 K (S5=on)
−
Control sequence 2-pipe fan coil c/o (changeover) heating = 0.8 K (S5=off)
−
The cycle time is 240 s. For safety reasons, max. 50 % of heating output is manual
possible at fan speed I (relay 120 s "on" and 120 s "off"), at speed II max. 80 % and at
speed III max. 100 %.
If no C/O (changeover) sensor is connected and terminals B2-M are open, the control-
ler is in cooling operation. Changeover to heating operation takes place manually on
the device. If a C/O sensor type QAH11 is connected, or terminals B2-M are getting
bridged by means of an external switch, changeover is automatic. The controller de-
tects a C/O sensor automatically. In this case, the manual C/O switch is deactivated.
Above the entry key of the changeover sensor, the types ACR12.320 and 340 are indi-
cating with LED`s, the operation of heating or cooling.
( See also on page 6: Factory settings )
The switching hysteresis is shown in the following diagram.
S11 = on
17°C
27°C
Changeover hysteresis
heating
cooling
Thermic valves with AC 230 V control must be used.
The control algorithm is optimised for STE2x actuators.
Motoric on/off valves must not be used.
The fan can be controlled in two different automatic operation modes (manual fan
speed selector switch on the controller set to "Auto"). Ventilation can remain set at
speed I in the neutral zone (control-free zone) or be switched off.The fan start from 0 to
stage 1 is linked with a booster call instruction, to beginn with stage 3 for 1 s to warrent
a safety start.
Fan coil controller for wall mounting ACR12
S11 = off
M off
T
35°C
17°C
M
fan
T
temperature
T
39°C
CE1N3573E
17.08.2001
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