Carrier 38AUZ*07 Series Installation, Start-Up And Service Instructions Manual page 13

LIQUID LINE
SIZE (in.)
3
/
8
1
/
2
5
/
8
38AUD units require TWO sets of parts.
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).
Table 9 — Refrigerant Specialities Part Numbers.
LIQUID LINE
SOLENOID VALVE (LLSV)
ALC-066208
ALC-066209
ALC-066212
LLSV SIGHT
COIL GLASS
AMG-24/50-60 HMI-1TT3
AMG-24/50-60 HMI-1TT4
AMG-24/50-60 HMI-1TT5
TXV
INDOOR SENSING
COIL CKT BULB
15 DIAMS
AIRFLOW
10
MIN
DIAMS
Single Circuit Coil Piping Configuration
For single compressor condensing units
TXV
INDOOR SENSING
COIL CKT 2 BULB
AIRFLOW 15 DIAMS
10
MIN
DIAMS
TXV
SENSING
INDOOR
BULB
COIL CKT 1
15 DIAMS
AIRFLOW
10
MIN
DIAMS
Dual Circuit Coil Piping Configuration
For single compressor condensing units
TXV — Thermostatic Expansion Valve
Fig. 7 — Location of Sight Glass(es) and Filter Driers
Typical 38AUZ Systems
13
FILTER
DRIER
Provided with unit
See Table 8
EQUALIZER LINE
SIGHT GLASS
A LOCATION
TXV FILTER DRIER
A LOCATION
8 DIAMS
MIN
EQUALIZER LINE
SIGHT GLASS
A LOCATION
TXV FILTER DRIER
CKT 2 A LOCATION
8 DIAMS
SIGHT
MIN
GLASSES
B LOCATION
FILTER
DRIERS
B LOCATION
TXV
CKT 1
8 DIAMS
MIN
LEGEND
DROP
CONTROL
SOLENOID
VALVE
DROP
CONTROL
SOLENOID
VALVE