Circuit Lead/Lag Selection (Multi-Circuit Units); Circuit Capacity Loading Sequence; High Condensing Temperature; Head Pressure Control - Carrier Touch Pilot Manual

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.
The.circuit.authorised.to.start.first.is.the.lead.circuit..Lead.
circuit.is.used.first.for.capacity.increases.and.at.the.same.time.
should be decreased last when decreasing capacity. The lead/
lag circuits can be selected manually or automatically
according.to.the.unit.configuration.(GEN_CONF).
• Automatic lead/lag circuit determination: The control
system determines the lead circuit to equalise the
operating.time.of.each.circuit.(value.weighted.by.the.
number of start-ups of each circuit). As a result, the
circuit with the lowest number of operating hours
always.starts.first.
• Manual lead/lag circuit determination: Circuit A or B
selected as the lead circuit. The selected circuit is always
the.leader..It.is.the.first.to.start.and.the.last.to.stop..

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
slide.valve..Three.types.of.sequencing.are.available.and.can.
be.configured.by.the.user.via.the.Touch.Pilot.user.interface.
(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
the.load.is.decreasing,.the.lag.circuit.is.unloaded.first..
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
Lead circuit (%) Lag circuit (%)
0 0
50 0
55 0
60 0
65 0
70 0
70 50
70 55
70 65
70 70
75 70
75 75
80 75
80 80
85 80
85 85
90 85
90 90
95 90
95 95
100 95
100 100
100 100
Unloading sequence
Lead circuit (%) Lag circuit (%)
100 100
100 95
95 95
95 90
90 90
90 85
85 85
85 80
80 80
80 75
75 75
75 70
70 70
70 65
65 65
65 60
60 60
60 55
60 50
60 0
55 0
50 0
0 0
7.12.2 - Dual circuit – staged capacity loading
Loading sequence
Lead circuit (%) Lag circuit (%)
0 0
50 0
55 0
60 0
65 0
70 0
75 0
80 0
85 0
90 0
95 0
100 0
100 50
100 55
100 60
100 65
100 70
100 75
100 80
100 85
100 90
100 95
100 100
7.12.3 - Dual circuit – smart capacity loading
Loading sequence
Lead circuit (%) Lag circuit (%)
0 0
50 0
55 0
60 0
65 0
70 0
75 0
80 0
85 0
90 0
95 0
100 0
70 50
70 55
70 60
70 65
70 70
75 70
75 75
80 75
80 80
85 80
85 85
90 85
90 90
95 90
95 95
100 95
100 100

7.13 - High condensing temperature

61XWHZE units are high condensing units for which the
maximum.condenser.leaving.water.temperature.can.be.set.
to 85°C.

7.14 - Head pressure control

For water-cooled 61XWHZE units, condensing pressure
control.is.assured.if.the.three-way.valve.option.is.selected..
The saturated condensing temperature is controlled based
on. a. user-configurable. fixed. setpoint. (SETPOINT. menu)..
The. three-way. valve. control. can. be. configured. only. by.
Carrier.service.technicians.
Unloading sequence
Lead circuit (%) Lag circuit (%)
100 100
100 95
100 90
100 85
100 80
100 75
100 70
100 65
100 60
100 55
100 50
95 50
90 50
85 50
80 50
75 50
70 50
70 0
65 0
60 0
55 0
50 0
0 0
Unloading sequence
Lead circuit (%) Lag circuit (%)
100 100
100 95
95 95
95 90
90 90
90 85
85 85
85 80
80 80
80 75
75 75
75 70
70 70
70 65
65 65
65 60
60 60
60 55
60 50
80 0
75 0
70 0
65 0
60 0
55 0
50 0
0 0
- -
- -
27