Control functions
2.2.2 Heating/Cooling function settings
Parameter Description
1 Basic setpoint (SP
basic)
2 Hysteresis used for setpoint calculation at Occupied state (heating and cooling)
3 Hysteresis used for setpoint calculation at Standby state (heating and cooling)
7
DeltaT, temperature span for On/Off control
Modbus register Modbus address Description
Holding register 1 Basic setpoint (SP
basic)
Holding register 2 Hysteresis used for setpoint calculation at Occupied state (heating and
cooling)
Holding register 3 Hysteresis used for setpoint calculation at Standby state (heating and cooling)
Holding register 4 DeltaT, temperature span for On/Off control
2.3 Change-over
2.3.1 General
Change-over is a control function that enables the thermostat to provide either a heating or a cooling signal
on the same output. This is achieved by shifting the change-over state from heating to cooling, and vice versa.
The change-over function makes it possible to use the thermostat in a 2-pipe change-over HVAC system,
where warm or cold media flow in the same pipes and one valve is used to regulate both heating and cooling
distribution.
The change-over state can be set to either heating or cooling.
The change-over state is managed with one of the available change-over modes:
✓ Manually heat
The thermostat works solely as a heating unit
✓ Manually cool
The thermostat works solely as an cooling unit
✓ Change-over, manual/automatic
The thermostat works as a heating or cooling unit depending on the change-over state. The change-
over may be set manually, by communication or by the temperature sensor on AI Temp or switch on
DI.
The heat or cool symbol is shown in the display depending on the current change-over state (heating or
cooling).
Figure 2-4 Heating symbol in the display at change-over state heating
Figure 2-5 Cooling symbol in the display at change-over state cooling
8 RCFD-230C manual, Rev. A
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