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In some cases the autotune function does not perform well or does not perform at all:

1.  The system is affected by process disturbances external to the control loop during autotuning (windows opened, load variation)

2.  The system is very dynamic. This is the case in which the heating or cooling power is too high for the volume of room regulated. 

Considering the conditions for autotuning cycle, some large overshoots can be verified.

3.  The system is very insulated and cannot cool down (heating season) or heat up (cooling season) in a timely manner. For such 

systems the autotuning cycle would take a very long time to complete with questionable results.

During autotuning the period of oscillations, overshoots and undershoots are measured. At the end of the cycle Bp, Ti parameters 

are calculated.

aPPEnDiX  2

Manual parameters setting

Proportional band

The width of the proportional band depends of the dynamics of the system. The first question to ask is, how strong must my 

output be to eliminate the error between the setpoint and temperature ?

The larger the proportional band (low gain), the less reactive the process. A proportional band too large, however, can lead to 

process wandering or sluggishness. The smaller the proportional band (high gain), the more reactive the output becomes. A 

proportional band too small, can lead to over-responsiveness leading to process oscillation.

A proportional band with is correct in width approaches the setpoint as fast as possible while minimizing overshoot. If a faster 

approach to setpoint is desired and process overshoot is not a problem, a smaller or narrower proportional band may be used.  

If process overshoot cannot be tolerated and the approach to setpoint does not have to be quick, a larger proportional band 

can be choosen.

integral time 

With proportional band alone, the process tend to reach a point away from setpoint. This offset is due to the difference betwe-

en the output needed to mantain setpoint and the ouptut of the proportional band at setpoint.

In the case of 2 pipe system with MAr=5V (50% of proportional band) if it is necessary a voltage different from 50% to mantain 

the setpoint, the offset is the difference between them.The integral action eliminates this difference. 

The integral action eliminates this difference by adding or substracting a value to the proportional action alone.

Integral time is the speed at which the controller corrects for offset. A short integral time means the controller corrects for offset 

quickly. If the integral time is too short, the controller would react before the effect of previous output shift, due to dead time or 

lag time, could be sensed causing oscillations. 

A long integral time means the controller corrects the offset over a long time. If the integral time is too long, the offset will remain 

for some time causing slow responding or sluggish control.

Proportional band with 

correct width

Proportional band 

too small

Proportional band 

too large

Summary of Contents for DB-TA-33A

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Page 2: ...ay Wait for another 4 s until is visualized the room temperature on the display The parameters are then saved and the unit is ready to do the regulation Instruction for other parameters setting level 2 or 3 To access the parameters of level 2 or 3 proceed with the following procedure Push until the message PAS is visualized on the display several seconds Push the value 6 0 appears on the display P...

Page 3: ...n direct action tI Integral time The integral time is the speed at which a corrective increase or decrease in ouput is made to compensate for offset which usually accompanies proportional only processes The more integral time entered the slower the action The less integral time entered the faster the action A too small integral time can make the system oscillating To exclude integral action and ma...

Page 4: ... setpoint for economy function in cooling mode independently of main setpoint SEt The unit works with main setpoint if the contact ECO connected between terminals 3 and 12 is open If contact is closed the unit works with economy cooling setpoint if cooling mode is selected Setting range 6 0 45 0 C default value 25 0 C SoH Economy setpoint for heatin It defines the setpoint for economy function in ...

Page 5: ...e the unit a proportional regulator set the value of parameter to noI with key Setting range 1 0 30 0 minutes with integral action noI without integral action default value 20 0 minutes dEZ Dead zone It defines the dead zone between heat and cool where there is not any regulation only for proportional action Setting range 0 5 4 0 C default value 1 0 C COr Correction of temperature It allows to add...

Page 6: ... 0 10 V heating output if at the beginning of autotuning cycle temperature is lower than setpoint On this case autotuning is done in heating If temperature is upper than the setpoint at the beginning of the autotuning cycle the active 0 10 V output is the cooling output The autotuning is done on this case in cooling Choose a level that avoid high oscillations Setting range 0 10 0 V default value 5...

Page 7: ... or minimum value of para meter calculated is assigned For instance if Ti calculated is upper than 30 minutes Ti max Ti is set to 30 If Ti calculated is lower than 1 minute the value 1 minute is set to parameter Ti Setting range no YES default value no TECHNICAL FEATURES Power supply 24 Vac 10 50 60 Hz Sensor internal NTC 10K or remote sensor NT0220 NTC10 02 code Measuring range 0 55 C Setpoint ra...

Page 8: ...unting or H05VC F otherwise APPENDIX 1 Autotuning The regulator calculates optimum parameters PI for the room regulated and save them in EEPROM so that when the controller is powered up after being shut down the controller does not need to be autotuned again The regulator use the same parameters until the cycle is again initiated The autotune parameters are only good for the process the autotune f...

Page 9: ...on A proportional band with is correct in width approaches the setpoint as fast as possible while minimizing overshoot If a faster approach to setpoint is desired and process overshoot is not a problem a smaller or narrower proportional band may be used If process overshoot cannot be tolerated and the approach to setpoint does not have to be quick a larger proportional band can be choosen Integral...

Page 10: ...the value in half Change the setpoint a little and observe how the system is reacting If the system is still sluggish and does not oscillate tighten by decrease the value in half again 5 Repeat the point 4 until the system begins to oscillate constantly 6 Multiply last proportional band set by 2 Integral time added 1 Set a large integral time 2 Change the setpoint a little and observe how the syst...

Page 11: ...et parameter POE to PI in order to use the unit as an automatic regulator T2 T1 K POE2 POE1 Subject to change without notice Tight the screws on the wall box MOUNTING OF THE UNIT AND CLOSING OF THE COVER OPENING THE COVER MOUNTING ON THE WALL SURFACE 1 tight the screws on the wall box 2 connect cables 3 push on the cover MOUNTING 1 2 3 110 DB TA_33A_EN_210715 ...

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