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For water [brine] circuits, if the Saturated Suction tempera-
ture falls below 34 F (1.1 C) [the Brine Freeze Point], the unit
capacity will not increase. If the Saturated Suction temperature
falls below 28 F (–2.2 C), [the Brine Freeze Point minus 6° F
(3.3° C)], for 90 seconds, all loaders in the circuit are turned
off. If this condition continues for a total of 3 minutes, the cir-
cuit will alarm and shut down.
High Condensing Temperature Unloading — Every 10 sec-
onds the control checks for the conditions below. Loaders will
be cycled as needed to control the saturated condensing tem-
perature below the configured maximum condensing tempera-
ture. Configured maximums are 154 F (67.8 C) for 30GX,
152 F (66.7 C) for 30HXA, and 122 F (50 C) for 30HXC units.
If a circuit's saturated condensing temperature is more than
12° F (6.7° C) below the maximum condensing temperature,
the circuit capacity is not allowed to increase. If the saturated
condensing temperature is more than 2° F (1.1° C) above the
maximum condensing temperature for 60 seconds, a loader is
turned off. If the saturated condensing temperature rises to
more than 5° F (2.8° C) above the maximum condensing tem-
perature during the 60 seconds, a loader is turned off immedi-
ately. If all the loaders were already off, the compressor is shut
down and an alarm is generated.
MOP (Maximum Operating Pressure) Override — The con-
trol monitors saturated condensing and suction temperature for
each circuit as well as differential oil pressure. Based on a con-
figurable maximum operating set point (saturated suction tem-
perature), set maximum condensing temperature, and mini-
mum differential oil pressure, the control may reduce the num-
ber of capacity stages being used and/or may lower the EXD
position when system pressures approach the set parameters.
Head Pressure Control
GENERAL — The microprocessor controls the condenser
fans (30GX) or water valve (30HXC) to maintain the saturated
condensing temperature to a configurable set point. The
30HXA condenserless units with a 09DK condenser use a
combination of factory-supplied fan cycling pressure switches
(shipped in the 30HXA control box), temperature switches,
and an accessory Motormaster
50DJ902811) or Motormaster III (part no. 30GT910-079) con-
trol to control head pressure independent of 30HXA unit con-
trol. The fans are staged or speed varied (30GX) or water valve
controlled (30HXC) based on each circuit's saturated condens-
ing temperature and compressor status. Water cooled units
(30HXC) operating at less than 70 F (21.1 C) for entering con-
denser water require the use of head pressure control.
The chiller must be field configured for the options shown
in Table 6. Fan stage settings are shown in Table 7.
47
8
46
45
7
44
43
6
42
5
41
LEGEND
LWT — Leaving Water
Temperature
®
(part no. 50DJ902801 or
DEADBAND EXAMPLE
0
200
STANDARD
DEADBAND
Fig. 4 — Deadband Multiplier
AIR-COOLED UNITS (30GX) — See Fig. 5 for condenser
fan locations.
Without Motormaster® Control — The first stage of fans are
turned on based on compressor status or a Head Pressure Set
Point based on Saturated Condensing Temperature (SCT).
Additional fan stages are added when the SCT exceeds the
Head Pressure Set Point. The Head Pressure Set Point is con-
figurable in the Set Point subfunction. The default is 113 F
(45 C). Once a fan stage has been added, the software tempo-
rarily modifies the head pressure set point by adding 15° F
(8.3° C) for 35 seconds. A fan stage will be removed when the
Saturated Condensing Temperature has been less than the
Head Pressure Set Point minus 35 F (19.4 C) for 2 minutes.
The control uses the higher of the 2 Saturated Condensing
Temperature values for 30GX080-150 and 160 units. For the
30GX151 and 161-350 units, each circuit's fan stages are inde-
pendently controlled based on the circuit Saturated Condens-
ing Temperature. Refer to Table 7 for condenser fan control
information. See Fig. 6A.
With Motormaster Control — For low-ambient operation, the
lead fan in each circuit can be equipped with the optional or
accessory Motormaster III head pressure controller. If factory
installed, the controller will be configured for 4 to 20 mA con-
trol. With the Motormaster III option enabled, the PSIO-1
module calculates the required output based on Saturated Con-
densing temperature, Head Pressure set point, and a PID (pro-
portional integral derivative) loop calculation. This 4 to 20 mA
output is driven through the PSIO-2 module. Proportional,
Integral, and Derivative gain parameters for air cooled controls
are adjustable and can be found in the Service subfunction.
Checkout and adjustment of the PID loop should only be
performed by certified Carrier Comfort Network technicians.
To obtain this accessory for field installation, order by part
number 30GX-900---012 for a single controller package
(30GX080-150 and 160). Order part number 30GX-900---014
for a dual controller package (30GX151 and 161-350). These
packages contain all the hardware required to install the acces-
sory. See Fig. 6B.
The control will use the higher of the 2 Saturated Condens-
ing Temperature values for 30GX080-150 and 160 units. For
the 30GX151 and 161-350 units, each circuit's fan stages are
independently controlled based on the circuit Saturated Con-
densing Temperature. Refer to Table 8 for condenser fan stag-
ing information.
400
600
TIME (SECONDS)
10
2 STARTS
800
1000
3 STARTS
MODIFIED
DEADBAND
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Troubleshooting
