9
Table 6 – Refrigerant Specialties Part Numbers
LIQUID LINE
SIZE (in.)
LIQUID LINE
SOLENOID VALVE (LLSV)
LLSV
COIL
SIGHT
GLASS
FILTER
DRIER
1
/
2
EF680035 EF680037 KM680004 KH43LS085
5
/
8
EF680036 EF680037 KM680005 KH43LS087
Check 38A UZD/E08 Model with Evaporator Coil
Connections —
Confirm before installation of unit that the evaporator coil
connec tions are consistent with the 38AUZD/E08.
Insulate Suction Lines —
Apply closed-cel l tubular insulation to all suction lines
betwee n evapora tor coil connection and 38AUZD/E08
unit’s suction service valve.
Refer to Tabl e 6 for recommendations on refrigeration
specialties.
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 suc tion lines at the outdoor unit.
Install Liquid Line Solenoid Valve —
It is recommended that a soleno id valve be placed in the
main liquid line (see Fig. 6) between the condensing unit
and the evap or ator coil. Locate th e soleno id 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 6. (A liquid line solenoid
valve is requ ired when the liquid line length exceeds 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. W ire the solenoid in
parallel with the compressor contactor coil (see Fig. 6). This
means of electrical control is referred to as soleno id dr op
control.
Single 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
LIQUID LINE
SOLENOID
VALVE
FLOW
C14291
Fig. 6 -- Location of Sight Glass and Filter Drier
Solenoid drop control wiring: Control the power to the
liquid line solenoid through a Solenoid Valve Relay (SVR)
in all units. Use part number HN 61PC005 (field--supplied,
installed). 38AU ZD/E08 unit requires one SV 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 t he evaporator load changed. Control
systems were used on these units that had the thermostat’ s
second stage contacts control a capaci ty control liquid line
solenoid valve to open or shutoff a portion of the
evapora tor 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 included automatic pressure --operated
unloading, check the existing thermostat and liquid
solenoid valve. When found, c onvert the evaporator
second stage solenoid control into a drop--sole noid
control.
Selecting an Accumulator –
Becaus e all 38A U models us e scro ll compr es s or s , an
accumulator is not required. If an accumulato r is to be
added, check the accumulato r manufactur er’s literatur e
carefully for indication of its su itability for use with
R--410A; look for minimum working pressure of 200 psig
(1380 kPa). Select the accumulator first on the basis of its
cataloged minimum capacity (tons ) to ensure oil return fro m
the accumulator, then on tub e size or ho ldin g capacity.
Make Piping Connections —
Piping connections at the 38AUZ unit are ba ll va lves with
stub tube extensions. Do not open the unit service valves
until all interconnecting tube brazing has been completed.
The stub tube connections include
1
/
4
-in SAE ser vice fittings
with Schrad er valve cor es (see Fig. 7). Befo re making any
brazed connections to the unit service valves, remove both
Schrader valve caps and cores and save for re-installation.
Con nect a sou rce for n itro gen to one of these service fitting s
during tube brazing to prevent the formation of copper
oxides inside the tubes at brazed jo ints .
When connecting the field tubing to the 38AUZ service
valves, wrap the valves in wet rags to preve nt 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 2-3 in-lbs
(23-34 N-cm).
38AU
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