Technichal Manual Heating Actuators AKH
MDT technologies GmbH •
51766 Engelskirchen
• Papiermühle 1
Tel.: +49-2263-
880 • Fax: +49
-2263-4588
• [email protected] • www.mdt.de
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4.5.6.1 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.)
4.5.6.2 Reset time
The reset time describes the I-amount of the controlling. The I-amount of a controlling causes an
integral convergence of the actual value to the setpoint. A short reset time indicates a strong I-
amount.
A short reset time causes that the control value approaches fast to the control value, which is set by
the proportional range. A big reset time causes a slow approach to this value.
To note is, that a reset time, which is adjusted too small, can cause across swinging. In principle you
can say each carrier the system, each bigger the reset time.
The following setting rules can be defined:
small reset time:
fast regulating of deviations; usage at fast systems and at places with
changing environmental conditions (disturbance variables like draft); danger of swinging
across
big reset time:
slow regulating of deviations; almost no danger for swinging across; usage at
slow systems as underfloor heating
