5.3 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.
Return temperature limitation
High limit Y2
Low limit Y1
Outdoor temp.
Low T out X2 High T out X1
The calculated limit is shown in brackets ( ) in the monitoring display.
See the section "Monitoring temperatures and system components".
MENU > Settings > Return limit
High T out X1 (return temp. limitation, high limit, X-axis)
1x031
Set the outdoor temperature value for the low return temperature limitation.
See Appendix “Parameter ID overview”
The corresponding Y coordinate is set in 'Low limit Y1'.
MENU > Settings > Return limit
Low limit Y1 (return temp. limitation, low limit, Y-axis)
1x032
Set the return temperature limitation referring to the outdoor temperature
value set in 'High T out X1'.
See Appendix “Parameter ID overview”
The corresponding X coordinate is set in 'High T out X1'.
MENU > Settings > Return limit
Low T out X2 (return temp. limitation, low limit, X-axis)
1x033
Set the outdoor temperature value for the high return temperature
limitation.
See Appendix “Parameter ID overview”
The corresponding Y coordinate is set in 'High limit Y2'.
76 | © Danfoss | 2017.09
VI.GU.T2.02
Operating Guide ECL Comfort 310, application A333
