Danfoss ECL Comfort 110 User Manual, Installation & Maintenance page 10

Return T limit (return temp. limitation)
The controller automatically changes the desired flow temperature to obtain an
acceptable return temperature when the return temperature falls below or gets higher
than the set limit.
Influence
This limitation is based on a PI regulation where P (Gain) responds quickly to deviations
and I (Intgr. time) responds slower and over time removes the small offsets between the
desired and actual values. This is done by changing the desired flow temperature.
If the 'Gain' is too high and / or the 'Intgr. time' too low, there is a risk of unstable control.
Limit (return temp. limitation)
Setting range
10 ... 110 °C
Set the return temperature you accept for the system.
Set the acceptable return temperature limit.
When the return temperature falls below or gets higher than the set value, the controller
automatically changes the desired flow temperature to obtain an acceptable return
temperature. The influence is set in lines 4035 and 4036.
18 VI.KT.G2.02
4000
'Gain - min.' > 0
'Limit'
'Gain max.' > 0
Return temperature
'Gain - max.' < 0
'Gain - min.' < 0
4030
Factory setting
50 °C
© Danfoss 05/2007 DH-SMT/DK
Gain - max. (return temp. limitation - max. influence)
Setting range
-9.9 ... 9.9
Determines how much the flow temperature will be influenced if the return temperature is higher than
the desired 'Limit' (line 4030) (P control).
Influence higher than 0:
The desired flow temperature is increased, when the return temperature gets higher
than the set limit.
Influence lower than 0:
The desired flow temperature is decreased, when the return temperature gets higher
than the set limit.
Example
The return limit is active above 50 °C.
The influence is set to -2.0.
The actual return temperature is 2 degrees too high.
Result:
The desired flow temperature is changed by -2.0 x 2 = -4.0 degrees.
Normally, the setting in line 4035 is lower than 0 in district heating systems to avoid a too
high return temperature.
Typically, the setting in line 4035 is 0 in boiler systems because a higher return temperature
is acceptable (see also line 4036).
Gain - min. (return temp. limitation - min. influence)
Setting range
-9.9 ... 9.9
Determines how much the flow temperature will be influenced if the return temperature is lower than
the desired 'Limit' (line 4030) (P control).
Influence higher than 0:
The desired flow temperature is increased, when the return temperature gets below the
set limit.
Influence lower than 0:
The desired flow temperature is decreased, when the return temperature gets below the
set limit.
VI.KT.G2.02
DH-SMT/DK
4035
Factory setting
-2.0
4036
Factory setting
0.0
© Danfoss 05/2007
19