Carrier Gemini 38AU 07 Series Installation, Start-Up And Service Instructions Manual page 13

TXV
SENSING
BULB
AIRFLOW
15 DIAMS
10
MIN
DIAMS
TXV
SENSING
BULB
AIRFLOW 15 DIAMS
10
MIN
DIAMS
SUCTION
CIRCUIT 1
SUCTION
CIRCUIT 2
DUAL CIRCUIT COIL PIPING CONFIGURATION
FOR TWO CIRCUIT CONDENSING UNITS
Fig. 10 — Location of Sight Glasses and Filter Driers
Typical 38AUD Systems
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.
A unit with two liquid line solenoid valves also requires a separate
control power transformer for the liquid solenoid valve loads. Se-
lect TRAN3 transformer part number according to unit power
supply.
QTY RELAY SVR QTY
MODEL
LSV - PART NUMBER
1 1 — HN61PC005
38AUZ
2 2 — HN61PC005
38AUDA,B
2 2 — HN61PC005
38AUDC 2 1 — HN61PC005*
LEGEND
LSV — Liquid Solenoid Valve
SVR
— Solenoid Valve Relay
N/R — Not Required
N/R # — Not Required / Factory Installed
* Install as SVR-2 (SVR-1 is factory-installed).
Mount the SVR (and transformer TRAN3 when used) in unit con-
trol box. Connect per wiring schematic label on unit.
NOTE: TRAN3 is provided with the HGBP factory installed op-
tion for 38AUDC12 units.
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
TRAN3 PRIMARY V:
PART NUMBER
N/R
208/230V: HT01BD202
460V: HT01BD702
575V: HT01BD902
N/R #
Evaporator Capacity Control Liquid Line Solenoid Valve
Many older unit designs included automatic capacity controls
that sensed changes in suction pressure and could increase or
decrease compressor capacity automatically as the evaporator
load changed. Control systems were used on these units that
had the thermostat's second stage contacts control a capacity
control liquid line solenoid valve to open or shutoff a portion
of the evaporator surface without any direct connection to the
compressor circuit.
This form of system capacity staging control is not possible with
38AU models. If this installation is a retrofit for a unit that includ-
ed automatic pressure-operated unloading, check the existing ther-
mostat and liquid solenoid valve. When found, convert the evapo-
rator second stage solenoid control into a drop-solenoid control.
Use the two SVR relays and transformer as required on 38AUD
models (above); wire the SVRs and transformer per two solenoid
valve systems.
SELECTING AN ACCUMULATOR
Because all 38AU models use scroll compressors, an accumulator
is not required. If an accumulator is to be added, check the accu-
mulator manufacturer's literature carefully for indication of its
suitability for use with R-410A; look for minimum working pres-
sure of 200 psig (1380 kPa). Select the accumulator first on the ba-
sis 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 intercon-
necting tube brazing has been completed. The stub tube connec-
tions include / -in. SAE service fittings with Schrader valve cores
1
4
(see Fig. 11). 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.
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 2 to 3 in-lbs (23 to 34 N-cm).
SERVICE VALVE
WITH STEM CAP
Fig. 11 — Typical Piping Connection Assembly
13
FACTORY
HIGH-FLOW
ACCESS PORT
FIELD SERVICE
ACCESS PORT
(SCHRADER CORE)
SWEAT
CONNECTION