Carrier Gemini 38AU 16-28 Series Installation, Start-Up And Service Instructions Manual page 13

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 (see Fig. 10) or 2 fil-
ter driers and sight glasses may be installed at B locations (see
Fig. 10 and 11).
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 liq-
uid line (see Fig. 10 and 11) 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 direc-
tion arrow pointed at the evaporator coil. Refer to Table 12. (A liq-
uid line solenoid valve is required when the liquid line length ex-
ceeds 75 ft [23 m].) 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. 10 and 11). This
means of electrical control is referred to as solenoid drop control.
TXV
INDOOR SENSING
COIL CKT BULB
AIRFLOW 15 DIAMS
10
MIN
DIAMS
8 DIAMS
Single Circuit Coil Piping Configuration
For Single Compressor Condensing Units
TXV
INDOOR SENSING
COIL CKT 2 BULB
15 DIAMS
AIRFLOW
10
MIN
DIAMS
8 DIAMS
TXV
SENSING
INDOOR
BULB
COIL CKT 1
AIRFLOW 15 DIAMS
10
MIN
DIAMS
Dual Circuit Coil Piping Configuration
For Single Compressor Condensing Units
Fig. 10 — Location of Sight Glass(es) and Filter
Driers Typical 38AUZ Systems
EQUALIZER LINE
SIGHT GLASS
A LOCATION
FILTER DRIER
A LOCATION
TXV
MIN
LIQUID LINE
SOLENOID
VALVE
EQUALIZER LINE
SIGHT GLASS
A LOCATION
TXV FILTER DRIER
CKT 2 A LOCATION
SIGHT
MIN
GLASSES
B LOCATION
FILTER
LIQUID LINE
DRIERS
SOLENOID
B LOCATION
VALVE
TXV
CKT 1
8 DIAMS
MIN
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. 11 — 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
38AUD 2 2 — HN61PC005
LEGEND
LSV — Liquid Solenoid Valve
SVR — Solenoid Valve Relay
N/R — Not Required
Mount the SVR (and transformer TRAN3 when used) in unit con-
trol box. Connect per wiring schematic label on unit.
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.
13
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