Carrier 38AUD Installation, Start-Up And Service Instructions Manual page 16

TXV
SENSING
BULB
AIRFLOW
15 DIAMS
10
MIN
DIAMS
TXV
SENSING
BULB
15 DIAMS
AIRFLOW
10
MIN
DIAMS
SUCTION
CIRCUIT 1
SUCTION
CIRCUIT 2
Dual Circuit Coil Piping Configuration
For two circuit condensing units
Fig. 8 - - Location of Sight Glasses and Filter Driers
Typical 38AUD Systems
Install Liquid Line Solenoid Valve —
It is recommended that a solenoid valve be placed in the
main liquid line (see Figs. 7 & 8) 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.
Solenoid drop control wiring: control the power to the
liquid line solenoid through a Solenoid Valve Relay (SVR)
in all units. Use part number HN61PC005 (field- - supplied,
installed). 38AUZ unit requires one SVR; 38AUD unit
requires two relays.
38AUD units also require a separate control power
transformer for the liquid solenoid valve loads. Use
transformer part number HT01BD602, according to unit
power supply.
Mount the SVR (and transformer TRAN3 when used) in
unit control box. Connect per wiring schematic label on
unit or per Fig. 24 (38AUZ) or Fig. 25 (38AUD).
Capacity Control Liquid
Evaporator capacity staging control via direct thermostat
control of a liquid solenoid valve on the evaporator's
second stage circuit is not possible with 38AU models. If
this installation is a retrofit for a unit that included
automatic pressure- - operated unloading, check the existing
thermostat and liquid solenoid valve wiring for possible
direct thermostat control of a solenoid valve; re- - wire per
Figs. 12 or 13 and 24 or 25.
Selecting an Accumulator –
Because all 38AU models use scroll compressors, an
accumulator is not required. If an accumulator is to be
added, check the accumulator manufacturer's literature
EQUALIZER LINE
TXV
CKT 2
8 DIAMS
MIN
SIGHT
GLASSES
LIQUID LINE
SOLENOID VALVE
FILTER
CIRCUIT 2
DRIERS
TXV
CKT 1
8 DIAMS
MIN
LIQUID LINE
SOLENOID VALVE
CIRCUIT 1
C10072
Line Solenoid Valve:
carefully for indication of its suitability for use with
R- - 410A; look for minimum working pressure of 1380 kPa
(200 psig). Select the accumulator first on the basis of its
cataloged minimum capacity (tons) to ensure oil return from
the accumulator, then on tube size or holding capacity.
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 brazing has been completed.
The stub tube connections include
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. Connect 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.
Factory
High-Flow
Access Port
Service Valve
with Stem Cap
Fig. 9 - - Typical Piping Connection Assembly
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).
Evacuation/Dehydration —
Evacuate and dehydrate the connected refrigeration
system(s) (excluding the 38AU unit) to 500 microns using
a two-stage vacuum pump attached to the service ports
outside the 38AU service valves, following description in
GTAC II, Module 4, System Dehydration.
WARNING
!
UNIT OPERATION AND SAFETY HAZARD
Failure to follow this warning could cause personal
injury, death and/or equipment damage.
R
Puron (R- - 410A) refrigerant systems operate at
higher pressure than standard R- - 22 systems. Do not
use R- - 22 service equipment or components on Puron
refrigerant equipment.
16
1
/ -in SAE service
4
Field Service
Access Port
(Schrader core)
Sweat
Connection
C10203