Specifications

29
Table 20 — Temperature Limits for
Standard 30MP Units
LEGEND
*For sustained operation, EWT should not exceed 85 F (29.4 C).
†Unit requires modification below this temperature.
VOLTAGE — ALL UNITS
Main Power Supply
— Minimum and maximum acceptable
supply voltages are listed in the Installation Instructions.
Unbalanced 3-Phase Supply Voltage — Never operate a motor
where a phase imbalance between phases is greater than 2%.
To determine percent voltage imbalance:
The maximum voltage deviation is the largest difference
between a voltage measurement across 2 legs and the average
across all 3 legs.
Example: Supply voltage is 240-3-60.
AB = 243 v
BC = 236 v
AC = 238 v
1. Determine average voltage:
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:
This voltage imbalance is satisfactory as it is below the
maximum allowable of 2%.
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
The unit is started by putting the ENABLE/OFF/REMOTE
CONTACT switch in the ENABLE or REMOTE CONTACT
position. When the unit receives a call for cooling (either from
the internal control or CCN network command or remote con-
tact closure), the unit stages up in capacity to maintain the leav-
ing fluid set point. The first compressor starts 1
1
/
2
to 3 minutes
after the call for cooling.
For all units, if temperature reset is being used, the unit con-
trols to a higher leaving-fluid temperature as the building load
reduces. If demand limit is used, the unit may temporarily be
unable to maintain the desired leaving-fluid temperature be-
cause of imposed power limitations.
SERVICE
Electronic Components
CONTROL COMPONENTS — Unit uses an advanced elec-
tronic control system that normally does not require service.
For details on controls refer to Controls section.
Access to the controls is through a hinged panel. Inner pan-
els are secured in place and should not be removed unless all
power to the chiller is off.
Compressor Replacement — All models contain
scroll compressors and have two or three compressors. A com-
pressor is most easily removed from the side of the unit or
above, depending on where clearance space was allowed dur-
ing unit installation. See Fig. 21.
Remove the junction box cover bolts and disconnect the
compressor power and crankcase heater connections (30MPA
only). Remove the cable from the compressor junction box.
Remove the connections from the high-pressure switch. Re-
move the crankcase heater. Knock the same holes out of the
new compressor junction box and install the cable connectors
from the old compressor.
The compressors are bolted to rails, which are in turn bolted
to the unit basepan for all sizes. Remove the 4 bolts holding the
compressor to the rail on the basepan. Save the mounting hard-
ware for use with the new compressor. Carefully cut the com-
pressor suction and discharge lines with a tubing cutter as close
to the compressor as feasible. Remove high-pressure switch
and pressure transducer(s) if required for compressor removal.
Lift one corner of the compressor at a time and remove all the
steel spacers. Remove the old compressor from the unit.
Slide the new compressor in place on the rails. Lifting one
side of the compressor at a time, replace all of the compressor
mounting hardware. Using new tubing as required, reconnect
compressor suction and discharge lines. Using hardware saved,
reinstall the mounting bolts and washers through the compres-
sor feet. Using proper techniques, braze suction and discharge
lines and check for leaks. Reconnect oil equalization line.
Re-install the crankcase heater (30MPA units). Reconnect
the compressor power connections and high-pressure switch
wiring as on the old compressor. Refer to Fig. 21. Following
TEMPERATURE LIMIT F C
Maximum Condenser LWT
140 60
Minimum Condenser EWT
65 18
Maximum Cooler EWT*
95 35
Maximum Cooler LWT
70 21
Minimum Cooler LWT†
40 4
EWT —
Entering Fluid (Water) Temperature
LWT —
Leaving Fluid (Water) Temperature
IMPORTANT: Medium temperature brine duty application
(below 32 F [0° C] LCWT) for chiller normally requires
factory modification. Contact your Carrier representative
for applicable LCWT range for standard water-cooled
chiller in a specific application.
% Voltage Imbalance = 100 x
max voltage deviation
from avg voltage
average voltage
Average voltage =
243 + 236 + 238
3
=
717
3
= 239
% Voltage Imbalance = 100 x
4
239
= 1.7%
IMPORTANT: If the supply voltage phase imbalance is
more than 2%, contact your local electric utility company
immediately. Do not operate unit until imbalance condition
is corrected.
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.