Carrier 38AU - Manual (Page 13)

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Table 9 — Refrigerant Specialities Part Numbers.
Refer to Table 9 for recommendations on refrigeration
specialties.
In some applications, depending on space and convenience re-
quirements, it may be desirable to install 2 filter driers and sight
glasses in a single circuit application. One filter drier and sight
glass may be installed at A locations in Fig. 7, or 2 filter driers
and sight glasses may be installed at B locations.
Select the filter drier for maximum unit capacity and minimum
pressure drop. Complete the refrigerant piping from the indoor
unit to the outdoor unit before opening the liquid and suction
lines at the outdoor unit.
INSTALL LIQUID LINE SOLENOID VALVE —
It is recommended that a solenoid valve be placed in the main
liquid line (see Fig. 7) between the condensing unit and the
evaporator coil. Locate the solenoid valve at the outlet end of
the liquid line, near the evaporator coil connections, with flow
direction arrow pointed at the evaporator coil. Refer to Table 9.
(A liquid line solenoid valve is required when the liquid line
length exceeds 23 m [75 ft].) This valve prevents refrigerant
migration (which causes oil dilution) to the compressor during
the off cycle, at low outdoor ambient temperatures. Wire the
solenoid in parallel with the compressor contactor coil (see
Fig. 7). This means of electrical control is referred to as sole-
noid drop control.
CAPACITY CONTROL LIQUID LINE SOLENOID VALVE
Evaporator capacity control via liquid solenoid valve is not rec-
ommended for use with 38AU models.
MAKE PIPING CONNECTIONS — Piping connections at
the 38AU unit are ball valves with stub tube extensions. Do not
open the unit service valves until all interconnecting tube braz-
ing as been completed.
The stub tube connections include ¼-in SAE service fittings
with Schrader valve cores (see Fig. 9). Before making any
brazed connections to the unit service valves, remove both
Schrader valve caps and cores and save for re-installation. Con-
nect a source for nitrogen to one of these service fittings during
tube brazing to prevent the formation of copper oxides inside
the tubes at brazed joints.
When connecting the field tubing to the 38AU service valves,
wrap the valves in wet rags to prevent overheating
Pressure-test all joints from outdoor unit connections over to
the evaporator coil, using nitrogen as pressure and with soap-
and-bubbles.
When pressure-testing is completed, remove the nitrogen
source at the outdoor unit service valves and re-install the two
Schrader valve cores. Torque the cores to 23-34 N-cm
(2-3 in-lbs).
Fig. 7 — Location of Sight Glass(es) and Filter Driers
Typical 38AUZ Systems
LIQUID LINE
SIZE (in.)
LIQUID LINE
SOLENOID VALVE (LLSV)
LLSV
COIL
SIGHT
GLASS
FILTER
DRIER
3 /
8
ALC-066208 AMG-24/50-60 HMI-1TT3
Provided with unit
See Table 8
1 /
2
ALC-066209 AMG-24/50-60 HMI-1TT4
5 /
8
ALC-066212 AMG-24/50-60 HMI-1TT5
38AUD units require TWO sets of parts.
INDOOR
COIL CKT 2
AIRFLOW
INDOOR
COIL CKT 1
AIRFLOW
15 DIAMS
MIN 10
DIAMS
8 DIAMS
MIN
TXV
SENSING
BULB
EQUALIZER LINE
SIGHT GLASS
A LOCATION
SIGHT
GLASSES
B LOCATION
TXV
CKT 2
FILTER DRIER
A LOCATION
FILTER
DRIERS
B LOCATION
DROP
CONTROL
SOLENOID
VALVE
FLOW
TXV
SENSING
BULB
TXV
CKT 1
8 DIAMS
MIN
15 DIAMS
MIN 10
DIAMS
Single Circuit Coil Piping Configuration
For single compressor condensing units
Dual Circuit Coil Piping Configuration
For single compressor condensing units
15 DIAMS
MIN 10
DIAMS
8 DIAMS
MIN
INDOOR
COIL CKT
AIRFLOW
TXV
SENSING
BULB
EQUALIZER LINE
SIGHT GLASS
A LOCATION
TXV FILTER DRIER
A LOCATION
DROP
CONTROL
SOLENOID
VALVE
FLOW
LEGEND
TXV — Thermostatic Expansion Valve