Return Limit - Danfoss ECL Comfort 210 Operating Manual

Operating Guide ECL Comfort 210/296/310, application A237/A337

5.4 Return limit

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.
DHW circuit
The return temperature limitation is based on a constant
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 temperature.
62 | © Danfoss | 2017.05
= 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".
= Return temperature
X
= Limitation temperature
# 1 #
= Negative influence (1x035) when return temp. gets higher than
# 2 #
limit. temp.
= Negative influence (1x036) when return temp. gets lower than
# 3 #
limit. temp.
= Positive influence (1x036) when return temp. gets lower than limit.
# 4 #
temp.
= Positive influence (1x035) when return temp. gets higher than
# 5 #
limit. temp.
If the 'Infl. ' factor is too high and / or the 'Adapt. time' too low, there is
a risk of unstable control.
VI.LG.R3.02