Parameter description:
P1: Setpoint / DeltaW for control circuit 2
Adjusting the setpoint of control circuit 2.
If A5=1, the setpoints for control circuit 1 and 2 are linked with one another via switching difference DeltaW,
which can be adjusted with P1. (operation with DeltaW)
The following applies: setpoint thermostat 2 = setpoint control circuit 1 + delta W2.
This difference can take positive or negative values. Thus, a leading or following contact can be realised.
P2: Hysteresis contact K1
P3: Hysteresis contact K2
The hysteresis can be set symmetrically or one-sided at the setpoint (see A40, A41).
At one-sided setting, the hysteresis works downward with heating contact and upward with cooling contact.
At symmetrical hysteresis, half of the hysteresis’ value is effective below and half of the value above the
switching point (see fig. 1 and 2).
Fig. 1:
Heating controller, one-sided hysteresis
Fig. 2:
Cooling controller, symmetrical hysteresis
P4: Control range limitation – minimum setpoint
P5: Control range limitation – maximum setpoint
The adjustment range of the setpoint can be limited in both directions. This is to prevent the end user of a
unit from setting inadmissible or dangerous setpoints.
P6: Actual value correction
This parameter allows the correction of actual value deviations caused for example by sensor tolerances or
extremely long sensor lines. The regulation measure value is increased or decreased by the here adjusted
value.
P19: Key-lock
The key-lock allows blocking of the control keys. In locked condition parameter adjustments with keys is not
possible. At the attempt to adjust the parameters despite key-lock the message "===" appears in the display.
P30: Lower alarm value
P31: Upper alarm value
The exit alarm is a boundary alarm or a range alarm with symmetrical hysteresis (see P32). Both at the
boundary alarm and the range alarm, limit values can be relative, i.e. going along with the setpoint, or
absolute, i.e. independent of the setpoint. The operation mode is set with parameter A30. If, in case of
boundary alarm and only one switching point is required the not used second switching point should be
adjusted to a value above or below the operating range of the controller.
Summary of Contents for ST72-31.03
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