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KNX ADVANCED COURSE

A room thermostat can be used as a two-step controller (thermostat) or as a continuous-
action controller (P / PI controller) both for pure heat or cool mode and for combined heat
and cool mode. The relevant application program compares the actual measured
temperature value with the required setpoint temperature value and calculates the
appropriate control variable.
The calculated control variable is then transmitted as a switching command (on/off) to the
actuators such as a binary output for controlling electrothermal valves (two-step control)
or as a control command (0 .... 100%) for controlling a motor-driven valve drive
(continuous control). Different operating states can be set both via external commands
and locally:
comfort, standby, night reduction, frost protection (when the windows are open or as a
permanent setting e.g. in the summer), which leads to a change in the setpoint value.

1.5.1 Two-step Individual Room Control

Figure 10: Behaviour of two-step control

Two-step control is characterised by the fact that there is a (slight) oscillation in the
steady state.

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