26 Chapter 8 Control principles RCF manual
Control principle at Heating/Cooling with electric heater
and change-over on DO5
RCF-230CTD(-EC) has a function for pulse/pause control of electric heaters. This function is
similar to the control of a thermal actuator.
When using an electric heater, the fan will run for an additional 2 minutes after the heater has
been shut down in order to cool it off. When an electric heater is used, an external unit (such
as PULSER-ADD or a solid state relay) must be connected between RCF-230CTD(-EC) and
the heater. NOTE: RCF-230CTD(-EC) has no indication capable of showing if the fan
breaks or if the heater should overheat. This requires all safety connections to be made
externally. An overheating protection or similar can be used to cut the supply voltage.
When using an electric heater while change-over is set to heating, RCF-230CTD(-EC) will
work using the sequence heating/heating, where DO5 will be activated first. If change-over is
set to cooling, DO5 will be the cooling output and DO4 will supply support heating if
needed.
If no change-over-sensor is used, cooling mode is activated using parameter 2 in the menu or
via SCADA communication.
The picture describes the DO4 and DO5 outputs as a function of the temperature when the
controller is set to Heating/Heating.
The picture describes the DO4 and DO5 outputs as a function of the temperature when
change-over is set to cooling control.
Min and max supply air limitation
Analogue input 1 (AI1) can be configured for use with a supply air temperature limitation
sensor. The controller will then automatically switch to cascade control. There are four
values for min and max limitation. The settable range is 10°C...50°C. The default setting is:
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