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19.1.1
Proportional Action
The proportional action sets a basic control action for what is currently happening. The value of this action is proportional to the
error, i.e. the deviation of the measured unit in relation to the setpoint.
This action is defined using the proportional constant K
Where B
is the value of the proportional band defined by one of the following parameters:
p
•
P20.18 (for temperature adjustment).
•
P20.21 (for humidity adjustment).
The proportional band B
defines the maximum error capable of bringing the proportional action to 100%.
p
A low B
value can therefore cause an extreme reaction even when there are slight variations in the error, while a high value
p
ensures little variation of the control variable even when there are serious errors.
The following table shows the reactions on the system caused by the decrease of the proportional band and resulting increase
of the proportional constant.
Parameter
Constant
(Decreases)
(Increases)
B
K
p
p
19.1.2
Integral Action
The integral action is an action of control on the basis of what has happened in the past. The value of this action is proportional
to the sum of the errors of the previous moments.
This action is defined using the integral constant K
T
is the value of the integral time defined by one of the following parameters:
i
•
P20.05 (for the adjustment of direct expansion units with on/off compressor or chilled water units).
•
P20.06 (for the adjustment of direct expansion units with inverter compressor).
•
P20.22 (for humidifier adjustment).
•
P20.95 (for the adjustment of direct expansion units with compressors with delivery air adjustment active and Free
Cooling).
The following table shows the reactions on the system caused by the decrease of the integral time and resulting increase of
the integral constant:
Parameter
Constant
(Decreases)
(Increases
)
T
K
i
i
The integral action can be disabled by setting the integral time to 0.
Version 38
(also known as proportional gain) calculated with this formula:
p
Promptness
Overshoot
of response
Increases
Increases
(also known as integral gain) calculated with this formula:
i
Promptness of
Overshoot
response
Increases
Increases
100
��
=
��
��
��
Balancing time
Decreases (slightly)
��
��
��
=
��
��
��
Balancing time
Increases
Error at full power
Stability
Decreases
Worsens
Error at full
Stability
power
Cancels out
Worsens
228
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