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Technical Manual – Room Temperature Controller SCN-RT1
The PI control continuous is a continuous controlling with proportional amount, the Proportional
range, and an integral amount, the reset time. The size of the proportional range is indicated in K,
whereas the I-amount is indicated in minutes.
The control value is controlled in steps from 0% to the adjusted maximum (have a look at 4.5.2.1 Max
value of control value) for the PI-control. A big deviation causes at normal direction, a big control
value to eliminate the deviation as fast as possible.
4.5.2.1 Max value of control value
By the setting "Max value of control value" can be adjusted which maximum value the control value
can assume. To prevent switching processes at large control values, a maximum can be defined by
the setting "Max value of control value". So the control value cannot exceed this value.
4.5.2.2 Heating/ cooling system
The control parameter (P-amount and I-amount) are adjusted by the setting for the used heating/
cooling system. You can use preset values, which fit to determined heating or cooling systems, or
parameterize the proportional range and the reset time freely. The preset values for the
corresponding heating or cooling system are based on empirical values and lead often to good
controlling results.
By choosing "Adjustment via control parameter", the proportional range and the reset time can be
parameterized freely. This setting requires a good knowledge in the field of control technology.
4.5.2.3 Proportional range
The proportional range describes the P-amount of the controlling. The P-amount produces a
proportional increment to the deviation of the control value.
A small proportional range causes a short recovery time of the deviation. The controller reacts
thereby almost immediately and sets the control value already at a small deviation almost to the
maximum value (=100%). If the proportional range is chosen too small, the system will swing across.
A proportional range of 4K means a control deviation of 4°C causes a control value of 100%. So a
control deviation of 1°C will cause a control value of 25%.
The following setting rules can be defined:
•
small proportional range: swing across possible at change of setpoint; usage at fast systems;
small recovery times
•
big proportional range: almost no danger of swing across; long recovery times, usage at slow
systems which need huge amplifications (big heating power etc.)
MDT technologies GmbH • 51766 Engelskirchen • Papiermühle 1
33
Phone: +49-2263-880 • Fax: +49-2263-4588 • knx@mdt.de • www.mdt.de
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