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instabus KNX/EIB System
Sensor
3. Switching 2-state control:
The 2-state control represents a very simple temperature control. For this type of control, two hysteresis
temperature values are predefined. The controller addresses the actuating elements via switch-on and switch-off
actuating variable commands (1-bit). A continuous actuating variable will not be calculated with this type of
control. The room temperature is evaluated periodically every 30 seconds as well, i.e. the actuating variables, if
required, will change only during these times.
While the 2-state temperature control is very simple, the fluctuating temperature is a disadvantage. For this
reason, no fast responding heating or cooling systems should be controlled via a 2-state control as it may result
in very strong temperature overshoot and thus in a loss of comfort.
When defining the hysteresis limit settings, one has to distinguish between the control options:
• Individual control options "heating" or "cooling":
While in heating mode the controller will switch-on the heater , if the temperature falls below a preset limit. In the
heating mode the controller will switch-off the heater only, if an adjusted temperature limit has been exceeded.
In the cooling mode the controller will switch-on the cooling, if the room temperature has exceeded a preset limit.
While in the cooling mode, the controller will switch-off the cooling only if the temperature has fallen below an
adjusted temperature limit.
Depending on the switching state of the actuating variable, a "1" or "0" will be output, if the value exceeds or
remains under the hysteresis limits.
In case of a 2-step control, the LEDs "heating" or "cooling" will light up or the signalling objects for heating and
cooling will already become active as soon as the temperature falls short of the temperature setpoint in case of
heating or exceeds the temperature setpoint in case of cooling. In this case, the hysteresis is not being
considered.
The upper and lower hysteresis limits are to be parameterized in the ETS for both control options.
The following figure shows a 2-state control for the individual control options "heating" or "cooling" (heating on the
left, cooling on the right; two temperature setpoints; one-stage heating or cooling; non-inverted actuating variable
output):
Room temperature
Setpt. temp. 2
Setpt. temp. 1
Variable
ON
OFF
An additional 2-state control heating or cooling stage works in exactly the same way as the 2-state control of the
basic stage. The difference is that the setpoint and the hysteresis values will shift by taking into account the
parameterized stage offset.
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Heating
Time
Time
Room temperature
Setpt. temp. 2
Setpt. temp. 1
Variable
ON
OFF
Cooling
07 /17
Subject to change without notice
Time
Time
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