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The stub tube connections include
1
/
4
-in SAE service
fittings with Schrader valve cores (see Fig. 10). 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
A
ccess Port
Service Valve
with Stem Cap
Field Service
Access Port
(Schrader core)
Sweat
Connection
C10203
Fig. 10 -- 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 2-3 in-lbs
(23-34 N-cm).
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.
UNIT OPERATION AND SAFETY HAZARD
Failure to follow this warning could cause personal
injury, death and/or equipment damage.
Puron
R
(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.
!
WARNING
This unit is designed for use with Puron (R--410A)
refrigerant. Do not use any other refrigerant in this
system.
Puron (R--410A) refrigerant is provided in pink (rose)
colored cylinders. These cylinders are available with and
without dip tubes; cylinders with dip tubes will have a
label indicating this feature. For a cylinder with a dip
tube, place the cylinder in the upright position (access
valve at the top) when removing liquid refrigerant for
charging. For a cylinder without a dip tube, invert the
cylinder (access valve on the bottom) when removing
liquid refrigerant.
Because Puron (R--410A) refrigerant is a blend, it is
strongly recommended that refrigerant always be removed
from the cylinder as a liquid. Admit liquid refrigerant into
the system in the discharge line. If adding refrigerant into
the suction line, use a commercial metering/expansion
device at the gauge manifold; remove liquid from the
cylinder, pass it through the metering device at the gauge
set and then pass it into the suction line as a vapor. Do not
remove Puron (R–410A) refrigerant from the cylinder as a
vapor.
Preliminary Charge —
Before starting the unit, charge R-410A liquid refrigerant
into the high side of each 38AU circuit through the liquid
service valve(s). The amount of refrigerant added must be
at least 80% of the operating charge listed in Tables 5 or 6
for LINEAR line length LESS the factory charge quantity
(if factory shipping charge has not been removed). See
example below.
Allow high and low side pressures to equalize. If pressures
do not equalize readily, charge R-410A vapor (using spe-
cial service manifold with expansion device) into the suc-
tion line service port for the low side of system to assure
charge in the evaporator. Refer to GTAC II, Module 5,
Charging, Recover, Recycling, and Reclamation for liquid
charging procedures.
Example:
38AUD*25 (RTPF)
60-ft (18.3 m) linear line length
Equivalent line length 90-ft (27.4 m)
Liquid Lift: 20-ft (6.1 m)
Select line sizes from Table 6 (38AUD):
Liquid
1
/
2
in
Suction 1-
1
/
8
in.
Charge
Circuit 1: 23.0 lbs (at 75-ft linear length)
Circuit 2: 22.0 lbs
80% of Operating Charge:
Circuit 1: 0.80 x 23.0 = 18.4 lbs
Circuit 2: 0.80 x 22.0 = 17.6 lbs
Factory Shipping Charge: 15 lbs
Field-Charge
Circuit 1: 18.4 -- 15 = 3.4 lbs
Circuit 2: 17.6 -- 15 = 2.6 lbs
For linear line lengths longer than 125 ft (38 m), contact
your local Carrier representative for system charge value.
Step 6 — Install Accessories
Accessories requiring modifications to unit wiring should
be completed now. These accessories may include Winter
Start controls and Low Ambient controls. Refer to the
instructions shipped with the accessory.
38AU