Operation Sequence; Service; Electronic Components; Control Components - Carrier AquaSnap 30RAP011-060 Controls, Start-Up, Operation, Service, And Troubleshooting

2. Determine maximum deviation from average voltage:
(AB) 243 – 239 = 4 v
(BC) 239 – 236 = 3 v
(AC) 239 – 238 = 1 v
Maximum deviation is 4 v.
3. Determine percent voltage imbalance:
% Voltage Imbalance = 100 x
This voltage imbalance is satisfactory as it is below the maximum
allowable of 2%.
IMPORTANT: If the supply voltage phase imbalance is more
than 2%, contact your local electric utility company immediate-
ly. Do not operate unit until imbalance condition is corrected.
Control Circuit Power
Power for the control circuit is supplied from the main incoming
power through a factory-installed control power transformer
(TRAN1) for all models. Field wiring connections are made to the
LVT.

OPERATION SEQUENCE

During unit off cycle, the control monitors the outdoor air tem-
perature. If the ambient temperature drops below 40°F (4.4°C),
cooler and hydronic system heaters (if either are factory installed)
are energized.
The unit is started by putting the Enable/Off/Remote Control
switch in the ENABLE or Remote Control position. When the
unit receives a call for cooling (either from the internal control or
CCN network command or Remote Control closure), the unit
stages up in capacity to maintain the leaving fluid set point. The
first compressor starts 1- / to 3 minutes after the call for cooling.
1
2
The lead circuit can be specifically designated on all models or se-
lected based on compressor run hours and starts depending on
field configuration. The unit control will override this selection
under certain starting conditions to properly maintain oil return to
the compressors. In general, on dual compressor circuits, the con-
trol will most often start the A1 or B1 compressor first, especially
after long off periods. The MBB controls fan stages to maintain
the head pressure set point and will automatically adjust unit ca-
pacity as required to keep compressors from operating outside of
the specified envelope. There are no pumpout or pumpdown se-
quences on these chillers.
For all units, if temperature reset is being used, the unit controls to
a higher leaving-fluid temperature as the building load reduces. If
demand limit is used, the unit may temporarily be unable to main-
tain the desired leaving-fluid temperature because of imposed
power limitations.

SERVICE

WARNING
Electrical shock can cause personal injury and death. Shut off
all power to this equipment during service. There may be more
than one disconnect switch. Tag all disconnect locations to
alert others not to restore power until work is completed.

Electronic Components

CONTROL COMPONENTS

Unit uses an advanced electronic control system that normally
does not require service.
4
239
= 1.7%
Access to the compressors is through latched panels from beneath
the control box on all models or from opposite the coil side (sizes
010-030 only). The front door(s) provide access to the compres-
sor(s) and all components of the refrigeration system. For size
010-030 units, access to the controls is through the upper latched
outer door above the compressor access door. Similarly, the upper
center latched door on sizes 035-150 gives access to the controls.
Inner panels are secured in place and should not be removed un-
less all power to the chiller is off.

Electronic Expansion Valve (EXV)

See Fig. 40 for a cutaway view of the EXV. High-pressure liquid
refrigerant enters valve through the top. As refrigerant passes
through the orifice, pressure drops and refrigerant changes to a 2-
phase condition (liquid and vapor). The electronic expansion
valve operates through an electronically controlled activation of a
stepper motor. The stepper motor stays in position, unless power
pulses initiate the two discrete sets of motor stator windings for
rotation in either direction. The direction depends on the phase
relationship of the power pulses.
As the stepper motor rotates, its motion is transferred to linear
movement by a lead screw. Refrigerant flow is modulated by ei-
ther opening or closing the port. The valve includes a positive
shut-off when closed.
1. Cable
2. Glass Seal
3. Motor Housing
4. Stepper Motor
5. Bearing
6. Lead Screw
7. Insert
8. Valve Piston
9. Valve Seat
10. Valve Port
Fig. 40 — Cutaway View of the Electronic
Expansion Valve (Size 070-150 Shown)
There are four different EXVs. Table 32 shows the number of
steps, by unit size, for each type of EXV. The EXV motor moves
at 200 or 150 steps per second, respectively, for sizes 010-060 or
sizes 070-150. Commanding the valve to either 0% or 100% will
add extra steps to the move, to ensure the value is open or closed
completely.
Table 32 — EXV Steps
UNIT SIZE 30RAP
010-020
025,030
035-045
050-060
070-090, 100 CKT A
100 CKT B, 110-150
The EXV board controls the valve. Each circuit has a thermistor
located in a well in the suction manifold before the compressor.
Suction pressure as measured by the suction pressure transducer is
54
EXV STEPS
1596
2500
1596
2500
2785
3690