Operation Sequence - Carrier 30GTN Service And Troubleshooting Manual

Consult application data section in the Product Data lit-
erature and job design requirements to determine flow rate
requirements for a particular installation.
Table 34 — Nominal and Minimum Cooler
Fluid Flow Rates
NOMINAL FLOW
30GTN,R
UNIT
SIZE
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. Fouling factor is .00001 ft
K/W).
NOTES:
1. Minimum flow based on 1.0 fps (0.30 m/s) velocity in cooler with-
out 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
MINIMUM FLOW
RATE* RATE (See Notes)
Gpm L/s Gpm
86 5.43 36.8
101 6.37 37.7
123 7.76 37.7
151 9.53 47.5
173 10.91 47.5
192 12.11 66.7
216 13.62 59.5
240 15.14 84.1
264 16.65 84.1
300 18.9 110
348 21.9 110
384 24.2 120
432 27.2 120
480 30.2 148
2
hr F/Btu (.000018 m
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-
control or CCN network command or remote contact clo-
sure), the unit stages up in capacity to maintain the cooler
fluid set point. The first compressor starts 1
after the call for cooling.
The lead circuit can be specifically designated or ran-
domly 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 con-
figuration is also available to determine if the unit should
L/s
stage up both circuits equally or load one circuit completely
before bringing on the other.
2.32
2.38
When the lead circuit compressor starts, the unit starts with
2.38
a pumpout routine. On units with the electronic expansion
3.00 valve (EXV), compressor starts and continues to run with
the EXV at minimum position for 10 seconds to purge the
3.00
refrigerant lines and cooler of refrigerant. The EXV then moves
4.20
to 23% and the compressor superheat control routine takes
3.75
over, modulating the valve to feed refrigerant into the cooler.
5.30
On units with thermostatic expansion valve (TXV)
5.30
(30GTN,R040,045 units with brine option), head pressure
6.9
control is based on set point control. When the lead com-
6.9
pressor starts, the liquid line solenoid valve (LLSV) is kept
7.5
closed for 15 seconds by a time delay relay. The micro-
processor stages fans to maintain the set point temperature
7.5
specified by the controller. There is no pumpout sequence
during shutdown of TXV controlled chillers.
9.3
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
operation, maintain set point of 113 F (45 C) as shipped from
factory. The default head pressure control method is set point
control. The head pressure control can also be set to EXV
control or a combination of the 2 methods between circuits.
2
For all units, if temperature reset is being used, the unit
controls to a higher leaving-fluid temperature as the build-
ing load reduces. If demand limit is used, the unit may tem-
porarily be unable to maintain the desired leaving-fluid tem-
perature because 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 closes,
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.
66
1 ⁄ to 3 minutes
2