Danfoss ECL Comfort 296 Operating Manual page 70

Operating Guide ECL Comfort 210 / 296, application A267
MENU > Settings > Control parameters
Nz (neutral zone)
When the actual flow temperature is within the neutral zone, the controller
does not activate the motorized control valve.
See Appendix "Parameter ID overview"
Set the acceptable flow temperature deviation.
Set the neutral zone to a high value if you can accept a high
variation in flow temperature.
MENU > Settings > Control parameters
Min. act. time (min. activation time gear motor)
The min. pulse period of 20 ms (milliseconds ) for activation of the gear
motor.
See Appendix "Parameter ID overview"
If you want to tune the PI regulation precisely, you can use the following method:
• Set the 'Tn' (integration time constant) to its max. value (999 sec.).
• Decrease the value for the 'Xp' (proportional band) until the system starts hunting (i.e. gets unstable) with a constant amplitude (it
might be necessary to force the system by setting an extreme low value).
• Find the critical time period on the temperature recorder or use a stop watch.
This critical time period will be characteristic for the system, and you can evaluate the settings from this critical period.
'Tn' = 0.85 x critical time period
'Xp' = 2.2 x proportional band value in the critical time period
If the regulation seems to be too slow, you can decrease the proportional band value by 10%. Make sure there is a consumption
when you set the parameters.
70 | © Danfoss | 2018.01
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Temp. Critical time period
The neutral zone is symmetrical around the desired flow temperature
value, i.e. half the value is above and half the value is below this
temperature.
Setting example
2
10
50
The setting should be kept as high as acceptable to increase the
lifetime of the actuator (gear motor).
Value x 20 ms
40 ms
200 ms
1000 ms
Time
VI.GU.G2.02