Pre-Start-Up; Digital Scroll Option; System Check; Configuring Minimum Load Control - Carrier AquaSnap 30MPA Series Controls, Start-Up, Operation, Service, And Troubleshooting

Digital Scroll Option —
a factory-installed option for a digital scroll compressor which
provides additional stages of unloading for the unit. The digital
compressor is always installed in the A1 compressor location.
When a digital compressor is installed, a digital unloader sole-
noid (DUS) is used on the digital compressor. Digital Scroll
Option not available for units controlled by the Multi-
Chiller Controller Accessory panel.
DIGITAL SCROLL OPERATION — A digital scroll oper-
ates in two stages — the "loaded state" when the solenoid
valve is de-energized and the "unloaded state" when the sole-
noid valve is energized. During the loaded state, the compres-
sor operates like a standard scroll and delivers full capacity and
mass flow.
However, during the unloaded state, there is no capacity
and no mass flow through the compressor. The capacity of the
system is varied by varying the time the compressor operates
in an unloaded and loaded state during a 15-second period. If
the DUS is energized for 7 seconds, the compressor will be
operating at 47% capacity. If the DUS is energized for 10 sec-
onds, the compressor will be operating at approximately 33%
of its capacity. Capacity is the time averaged summation of
loaded and unloaded states, and its range is continuous from
the minimum configured capacity to 100%. Regardless of
capacity, the compressor always rotates with constant speed.
As the compressor transitions from a loaded to unloaded state,
the discharge and suction pressures will fluctuate and the com-
pressor sound will change.
The ComfortLink controller controls and integrates the op-
eration of the DUS into the compressor staging routine to
maintain temperature control. When a digital compressor is in-
stalled, an additional discharge gas temperature thermistor
(DTT) is installed along with the AUX board for control of the
DUS.
DIGITAL COMPRESSOR CONFIGURATION — When a
digital compressor is installed, the configuration parameter
 
(Configuration UNIT A1.TY) is configured to YES.
There is also a maximum unload time configuration, (Config-
 
uration UNIT MAX.T) that is set to 10 seconds (sizes
020,030) or 7 seconds (sizes 040,045), which indicates the
maximum unloading for the digital compressor is 47%. This is
done to optimize efficiency of the system.
MINIMUM LOAD CONTROL — Minimum load control is
generally not recommended for split systems. If installed, the
feature must be enabled in the controls. Minimum load control
or hot gas bypass cannot be used in conjunction with the digital
scroll option.
Minimum load control can only be added to standard com-
pressor units in the field. This feature will not operate with an
optional digital compressor and when the digital function is en-

abled (Configuration Unit
minimum load valve, confirm that the digital compressor op-
tion is disabled and set Minimum Load Valve Select to YES,
 
(Configuration OPT1 MLV.S=YES). See Table 32.
NOTE: Minimum Load Control and Digital Compressor oper-
ation cannot be used together.
Table 32 — Configuring Minimum Load Control
CONFIGURATIONUNIT
ITEM EXPANSION
Compressor A1
A1.TY
Digital?
CONFIGURATIONOPT1
Minimum Load Vlv
MLV.S
Select
The 30MP020-045 units have

A1.TY=YES). To enable the
COMMENTS
Range: NO/YES
Default: Depends on prod-
uct configuration
NO = Not Equipped
Value must be set to NO
Range: NO/YES
Default: NO
Set to YES to activate
If equipped and enabled, the Minimum Load Control valve
is active as the last stage of capacity when the unit is unloading.
MAINTENANCE REMINDER — The 30MP ComfortLink
controls have the ability to provide a reminder for service per-
sonnel that regularly scheduled strainer maintenance is re-
quired. Maintenance interval is a field-configurable item. The
service interval should be adjusted for the job site conditions.
See Table 33.
Table 33 — Configuring Maintenance Reminder
RUN STATUSPMSTRN
ITEM EXPANSION
SI.ST Strainer Srvc Interval

PRE-START-UP

IMPORTANT: Before beginning Pre-Start-Up or Start-Up,
complete Start-Up Checklist for 30MP Liquid Chiller at
end of this publication (pages CL-1 to CL-8). The checklist
assures proper start-up of a unit, and provides a record of
unit condition, application requirements, system informa-
tion, and operation at initial start-up.
Do not attempt to start the chiller until following checks
have been completed.

System Check

1. Check all auxiliary components, such as chilled fluid
pumps, air-handling equipment, condenser pump or other
equipment to which the chiller supplies liquid. Consult
manufacturer's instructions. Verify that any pump inter-
lock contacts have been properly installed. If the unit has
field-installed accessories, be sure all are properly in-
stalled and wired correctly. Refer to unit wiring diagrams.
2. Use the scrolling marquee display to adjust the Cooling
Set Point.
3. Fill chilled fluid circuit with clean water (with recom-
mended inhibitor added) or other non-corrosive fluid to
be cooled. Bleed all air out of the high points of the sys-
tem. If chilled water is to be maintained at a temperature
below 40 F (4.4 C), a brine of sufficient concentration
must be used to prevent freeze-up at anticipated suction
temperatures. To ensure sufficient loop volume, see
Tables 34 and 35.
4. Check tightness of all electrical connections.
5. Oil should be visible in the compressor sight glass(es).
See Fig. 25. An acceptable oil level in the compressors is
from 1 / to 3 / of sight glass when the compressors are off.
8 8
Adjust the oil level as required. See Oil Charge section on
page 45 for Carrier approved oils.
6. Crankcase heaters must be firmly attached to compres-
sors, and must be on for 24 hours prior to start-up
(30MPA015-045, 30MPA,MPW050-071 only).
7. Electrical power source must agree with unit nameplate.
8. Check rotation of scroll compressors. Monitor control
alarms during first compressor start-up for reverse rota-
tion protection alarm.
36
COMMENTS
Range: 0 to 65,500 hrs
Default: 8760 hrs
Setting SI.ST to 0 disables
the feature