Return Limit - Danfoss ECL Comfort 210 Operating Manual

Operating Guide ECL Comfort 210/296/310, application A232 / A332

5.4 Return limit

The return temperature limitation is based on a selectable
temperature value. 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.
This limitation is based on a PI regulation where P ('Infl.' factor)
responds quickly to deviations and I ('Adapt. time') responds slower
and over time removes the small offsets between the desired and
actual values. This is done by changing the desired flow / duct
temperature.
Typical for heating systems is that the return temperature must be
as low as possible.
Typical for cooling systems is that the return temperature must be
as high as possible.
Some parameter descriptions refer to "duct temperature" because
the parameter in question is used in other applications too.
Some parameter descriptions refer to "surface temperature"
because the parameter in question is used in other applications too.
The return temperature limitation is based on the outdoor
temperature. Typically in district heating systems a higher return
temperature is accepted at a decrease in outdoor temperature. The
relationship between the return temperature limits and outdoor
temperature is set in two coordinates.
The outdoor temperature coordinates are set in 'High T out X1'
and 'Low T out X2' . The return temperature coordinates are set in
'High limit Y2' and 'Low limit Y1' .
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 calculated limit.
This limitation is based on a PI regulation where P ('Infl.' factor)
responds quickly to deviations and I ('Adapt. 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.
76 | © Danfoss | 2017.08
Influence
If the 'Infl. ' factor is too high and / or the 'Adapt. time' too low, there is
a risk of unstable control.
= Outdoor temperature
X
= Limitation temperature
Y
= High T out (1x031)
# X1 #
= Low T out (1x033)
# X2 #
= Low limit (1x032)
# Y1#
= High limit (1x034)
# Y2 #
The calculated limit is shown in brackets ( ) in the monitoring display.
See the section "Monitoring temperatures and system components".
'Infl. - min.' > 0
'Limit'
'Infl. - max.' > 0
Return temperature
'Infl. - max.' < 0
'Infl. - min.' < 0
VI.JM.G2.02