Data Sheet for Product

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Building Technologies Fan coil controller for wall mounting ACR12 CE1N3578en
HVAC Products 03.10.2005
Changeover between heating and cooling operation
Controllers for 4 pipe fan-coils change automatically between heating and cooling.
Controllers for 2 pipe fan-coils need information about the water temperature. They
receive this information either from a water temperature sensor (changeover sensor) or
from a remote central station or from the operator through the C/O (changeover) key.
If no C/O sensor is connected and the terminals B2-M are open and P18 = 1 (if avail-
able) then the C/O key on the controller is active and is used for switching between
heating and cooling. Pressing the key once switches the mode immediately and the
new active mode is shown by the heating or cooling symbol or by the LEDs.
With a remote switch connected to the terminals B2-M then the controller is in cooling
operation when the switch is open or in heating when the switch is closed. Since an
open input also enables manual switching, a resistor of 10 K Ohm must be connected
to B2-M (in parallel to the contact) or the manual switching must be inhibited by P18 = 0
(if parameter entry is available). Note that if P18 = 0 then the 10 K Ohm resistor is not
used to inhibit the manual switching.
If a C/O sensor type QAH11 is connected to the terminals B2-M for measuring the wa-
ter temperature then the diagrams below show the switching between heating an cool-
ing (note that the behaviour depends on P11):
P11 = ON or 1
Hysteresis between 17°C and 27 °C
P11 = OFF or 0
Hysteresis between 17°C and 39 °C
Fan is switched OFF if the water temperature
falls below 35 °C in heating mode
17°C
39°C
T
27°C
T
3574D05
35°C
Fan OFF
if Heating
17°C
heating
T water temperature
cooling
Manual changeover
Remote changeover
Local changeover