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7.11 - Circuit lead/lag selection (multi-circuit units)
This function determines the lead and lag circuit on dual-
circuit units. It controls the start/stop sequence of the
refrigeration circuits called circuit A or circuit B.
should be decreased last when decreasing capacity. The lead/
lag circuits can be selected manually or automatically
• Automatic lead/lag circuit determination: The control
system determines the lead circuit to equalise the
number of start-ups of each circuit). As a result, the
circuit with the lowest number of operating hours
• Manual lead/lag circuit determination: Circuit A or B
selected as the lead circuit. The selected circuit is always
7.12 - Circuit capacity loading sequence
This function determines in which order the circuit capacity
is changed. Compressor loading is managed by starting/
stopping the compressors and controlling the position of the
(GEN_CONF).
• Balanced loading sequence: The control maintains
equal capacity between all circuits as the machine loads
and unloads. See also section 7.12.1.
• Staged loading sequence: The control loads the lead
circuit completely before the lag circuit is started. When
See also section 7.12.2.
• Smart circuit loading: The control loads the lead circuit
completely before decreasing in order to make the
global unit load increasing smoother. For unloading
sequence the lead circuit is increased when the lag
circuit is stopped. See also section 7.12.3.
7.12.1 - Dual circuit – balanced capacity loading
Loading sequence Unloading sequence
Lead circuit (%) Lag circuit (%) Lead circuit (%) Lag circuit (%)
0 0 100 100
50 0 100 95
55 0 95 95
60 0 95 90
65 0 90 90
70 0 90 85
70 50 85 85
70 55 85 80
70 65 80 80
70 70 80 75
75 70 75 75
75 75 75 70
80 75 70 70
80 80 70 65
85 80 65 65
85 85 65 60
90 85 60 60
90 90 60 55
95 90 60 50
95 95 60 0
100 95 55 0
100 100 50 0
100 100 0 0
7.12.2 - Dual circuit – staged capacity loading
Loading sequence Unloading sequence
Lead circuit (%) Lag circuit (%) Lead circuit (%) Lag circuit (%)
0 0 100 100
50 0 100 95
55 0 100 90
60 0 100 85
65 0 100 80
70 0 100 75
75 0 100 70
80 0 100 65
85 0 100 60
90 0 100 55
95 0 100 50
100 0 95 50
100 50 90 50
100 55 85 50
100 60 80 50
100 65 75 50
100 70 70 50
100 75 70 0
100 80 65 0
100 85 60 0
100 90 55 0
100 95 50 0
100 100 0 0
7.12.3 - Dual circuit – smart capacity loading
Loading sequence Unloading sequence
Lead circuit (%) Lag circuit (%) Lead circuit (%) Lag circuit (%)
0 0 100 100
50 0 100 95
55 0 95 95
60 0 95 90
65 0 90 90
70 0 90 85
75 0 85 85
80 0 85 80
85 0 80 80
90 0 80 75
95 0 75 75
100 0 75 70
70 50 70 70
70 55 70 65
70 60 65 65
70 65 65 60
70 70 60 60
75 70 60 55
75 75 60 50
80 75 80 0
80 80 75 0
85 80 70 0
85 85 65 0
90 85 60 0
90 90 55 0
95 90 50 0
95 95 0 0
100 95 - -
100 100 - -
7.13 - High condensing temperature
61XWHZE units are high condensing units for which the
to 85°C.
7.14 - Head pressure control
For water-cooled 61XWHZE units, condensing pressure
The saturated condensing temperature is controlled based
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