Point A: At start-up the temperature will be higher than wanted in the evaporator and therefore a higher pressure than the Cut-in level and the compressor

must run. Another situation could be that the start situation is where the feedback is between Cut-out and Cut-in. In that case no STOP is initiated.

Point B: After some time the cut-out level may be reached and the compressor must be shut off.

Point C: Cut-in is reached and the compressor is restarted.

NB!

When using the TPF together with the Pack Controller further consideration must be taken. The Cut-Out value should be below the -

Zone setting (see par 25-22). Cut-In should be set above the set-point and within the neutral zone (par. 25-20).

20-40 Thermostat/Pressostat Function

Set whether the Thermostat/ Pressostat function is active (On) or inactive (Off).

Option:

[0] *

Off

[1]

20-41 Cut-out Value

Range:

1 bar*

[-3000 - par.20-42]

20-42 Cut-in Value

Range:

3 bar*

[Par. 20-41 - 3000]

3.15.6 20-7* PID autotuning

The frequency converter PID Closed Loop controller (parameters 20-**, FC Closed Loop) can be auto-tuned, simplifying and saving time during com-

missioning, whilst ensuring accurate PID control adjustment. To use auto-tuning it is necessary for the frequency converter to be configured for closed

Configuration Mode

loop in par.1-00

A Graphical Local Control Panel (LCP) must be used in order to react on messages during the auto-tuning sequence.

Enabling par.20-79

PID Autotuning

, puts the frequency converter into auto-tuning mode. The LCP then directs the user with on-screen instructions.

The fan/pump is started by pressing [Auto On] button on the LCP and applying a start signal. The speed is adjusted manually by pressing the [

▼

[

] navigation keys on the LCP to a level where the feedback is around the system set-point.

NB!

It is not possible to run the motor at maximum or minimum speed, when manually adjusting the motor speed due to the need of giving

the motor a step in the speed during auto-tuning.

PID auto-tuning functions by introducing step changes whilst operating at a steady state and then monitoring the feedback. From the feedback response,

PID Proportional Gain

the required values for par.20-93

value 0 (zero). par. 20-81

PID Normal/ Inverse Control

These calculated values are presented on the LCP and the user can decide whether to accept or reject them. Once accepted, the values are written to

the relevant parameters and auto-tuning mode is disabled in par.20-79

carry out auto-tuning could be several minutes.

It is advised to set the ramp times in par.3-41

Ramp 2 Ramp Down Time

3-52

according to the load inertia before carrying out PID autotuning. If PID autotuning is carried out with slow ramp times,

Function: