Flow Rate Requirements; Operation Sequence; Refrigerant Circuit; Field Wiring - Carrier Air Conditioner Operation And Service Manual

Consult application data section in the Product Data litera-
ture and job design requirements to determine flow rate re-
quirements for a particular installation.
Table 36 — Nominal and Minimum Cooler
Fluid Flow Rates
UNIT SIZE
30GTN,R
AND 30GUN,R
Gpm
040
045
050
060
070
080,230B
090,245B
100,255B,270B
110,290B,315B
130
150,230A-255A
170,270A,330A/B,
360B (50 Hz)
190,290A,360A/B (60 Hz),
360A (50 Hz), 390B
210,315A,390A,420A/B
LEGEND
ARI — Air Conditioning and Refrigeration Institute
Gpm — Gallons per minute (U.S.)
L/s — Liters per second
N — Liters per kW
V — Gallons per ton
*Nominal flow rates required at ARI conditions are 44 F (6.7 C) leaving-fluid
temperature, 54 F (12.2 C) entering-fluid temperature, 95 F(35 C) ambient.
⋅ hr ⋅ F/Btu (.000018 m
2
Fouling factor is .00001 ft
NOTES:
1. Minimum flow based on 1.0 fps (0.30 m/s) velocity in cooler without special
cooler baffling.
2. Minimum Loop Volumes:
Gallons = V x ARI Cap. in tons
Liters = N x ARI Cap. in kW
APPLICATION
Normal Air Conditioning
Process Type Cooling
Low Ambient Unit Operation
Operation Sequence —
case heaters are energized. If ambient temperature is below
36 F (2 C), cooler heaters (if equipped) are energized.
The unit is started by putting the ENABLE/OFF/REMOTE
CONTACT switch in ENABLE or REMOTE position. When
the unit receives a call for cooling (either from the internal
control or CCN network command or remote contact closure),
the unit stages up in capacity to maintain the cooler fluid set
point. The first compressor starts 1
for cooling.
The lead circuit can be specifically designated or randomly
selected by the controls, depending on how the unit is field
configured (for 040-070 sizes, Circuit A leads unless an
accessory unloader is installed on Circuit B). A field configura-
tion is also available to determine if the unit should stage up
both circuits equally or load one circuit completely before
bringing on the other.
When the lead circuit compressor starts, the unit starts with
a pumpout routine. On units with the electronic expansion
valve (EXV), compressor starts and continues to run with the
EXV at minimum position for 10 seconds to purge the refriger-
ant lines and cooler of refrigerant. The EXV then moves to
23% and the compressor superheat control routine takes over,
modulating the valve to feed refrigerant into the cooler.
On units with thermostatic expansion valve (TXV)
(30GTN,R and 30GUN,R 040,045 units with brine option),
head pressure control is based on set point control. When the
lead compressor starts, the liquid line solenoid valve (LLSV) is
MINIMUM
NOMINAL
FLOW RATE
FLOW RATE*
(See Notes)
L/s Gpm L/s
86 5.43 36.8 2.32
101 6.37 37.7 2.38
123 7.76 37.7 2.38
151 9.53 47.5 3.00
173 10.91 47.5 3.00
192 12.11 66.7 4.20
216 13.62 59.5 3.75
240 15.14 84.1 5.30
264 16.65 84.1 5.30
300 18.9 110 6.9
348 21.9 110 6.9
384 24.2 120 7.5
432 27.2 120 7.5
480 30.2 148 9.3
⋅ K/W).
2
V N
3 3.25
6 to 10 6.5 to 10.8
6 to 10 6.5 to 10.8
During unit off cycle, crank-
1
/ to 3 minutes after the call
2
kept closed for 15 seconds by a time delay relay. The micropro-
cessor stages fans to maintain the set point temperature speci-
fied by the controller. There is no pumpout sequence during
shutdown of TXV controlled chillers.
On all other units (EXV units), the head pressure is con-
trolled by fan cycling. The desired head pressure set point is
entered, and is controlled by EXV position or saturated con-
densing temperature measurement (T3 and T4). For proper op-
eration, maintain set point of 113 F (45 C) as shipped from fac-
tory. The default head pressure control method is set point con-
trol. The head pressure control can also be set to EXV control
or a combination of the 2 methods between circuits.
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.
On EXV units, when the occupied period ends, or when the
building load drops low enough, the lag compressors shut
down. The lead compressors continue to run as the EXV clos-
es, and until the conditions of pumpout are satisfied. If a fault
condition is signaled requiring immediate shutdown, pumpout
is omitted.
Loading sequence for compressors is shown in Tables 5A
and 5B.

Refrigerant Circuit

LEAK TESTING — Units are shipped with complete operat-
ing charge of refrigerant R-22 for 30GTN,R and R-134a for
30GUN,R (see Physical Data tables supplied in the chiller's
installation instructions) and should be under sufficient pres-
sure to conduct a leak test. If there is no pressure in the system,
introduce enough nitrogen to search for the leak. Repair the
leak using good refrigeration practices. After leaks are
repaired, system must be evacuated and dehydrated.
REFRIGERANT CHARGE (Refer to Physical Data tables
supplied in the chiller's installation instructions) — Immedi-
ately ahead of filter drier in each circuit is a factory-installed
liquid line service valve. Each valve has a
nection for charging liquid refrigerant.
Charging with Unit Off and Evacuated — Close liquid line
service valve before charging. Weigh in charge shown on unit
nameplate (also in Physical Data tables supplied in the chiller's
installation instructions). Open liquid line service valve; start
unit and allow it to run several minutes fully loaded. Check for
a clear sight glass. Be sure clear condition is liquid and not
vapor.
Charging with Unit Running — If charge is to be added while
unit is operating, all condenser fans and compressors must be
operating. It may be necessary to block condenser coils at low
ambient temperatures to raise condensing pressure to approxi-
mately 280 psig (1931 kPa) to turn all condenser fans on. Do
not totally block a coil to do this. Partially block all coils in uni-
form pattern. Charge each circuit until sight glass shows clear
liquid, then weigh in amount over a clear sight glass as listed
in Physical data tables supplied in chiller's installation
instructions.
IMPORTANT: When adjusting refrigerant charge, circu-
late fluid through cooler continuously to prevent freez-
ing and possible damage to the cooler. Do not
overcharge, and never charge liquid into low-pressure
side of system.

FIELD WIRING

Field wiring is shown in Fig. 36-41.
67
1
/ -in. Schrader con-
4