Carrier 38TN Service Manual page 12

Fig. 16—Leak Detector
Due to the high pressure of nitrogen, it should never be used
without a pressure regulator on the tank.
Assuming that a system is pressurized with either all refrigerant or
a mixture of nitrogen and refrigerant, leaks in the system can be
found with a leak detector which detects extremely small refrig-
erant leaks.
If system has been operating for some time, make first check for
a leak visually. Since refrigerant carries a small quantity of oil,
traces of oil at any joint or connection is an indication that
refrigerant is leaking at that point.
A simple and inexpensive method of testing for leaks is to use soap
bubbles. Any solution of water and soap may be used. Soap
solution is applied to all joints and connections in system. A small
pinhole leak is located by tracing bubbles in soap solution around
leak.
Use electronic leak detector to check for leaks. This unquestion-
ably is the most efficient and easiest method for checking leaks.
There are various types of electronic leak detectors. Electronic leak
detectors must be suitable for R134A application. Check with the
manufacturer of the equipment for suitability. Generally speaking,
they are all portable, most are lightweight, and consist of a box
with several switches and a probe or sniffer. Detector is turned on
and probe is passed around all fittings and connections in system.
Leak is detected by either the movement of a pointer on detector
dial, a buzzing sound, or a light.
In all instances when a leak is found, system charge must be bled
down and leak repaired before final charging and operation. After
leak testing or leak is repaired, evacuate system reclaiming
refrigerant and recharge with correct refrigerant charge.
Step 3—Brazing
When brazing is required in the refrigeration system, certain basics
should be remembered. The following are a few of the basic rules.
1. Clean joints make the best joints. To clean:
a. Remove all oxidation from surfaces to a shiny finish before
brazing.
b. Remove all flux residue with brush and water while
material is still hot.
2. Use "sil-fos" or "phos-copper" for copper-to-copper only. No
flux is required.
3. Silver solder is used on copper-to-brass, copper-to-steel, or
copper-to-copper. Flux is required when using silver solder.
4. Fluxes should be used carefully. Avoid excessive application
and do not allow fluxes to enter into the system.
5. Brazing temperature of copper is proper when it is heated to a
dull red color.
This section on brazing is not intended to teach a technician how
to braze. There are books and classes which teach and refine
brazing techniques. The basic points above are listed only as a
reminder.
Step 4—Service Valves
Service valves provide a means for holding original factory charge
in outdoor unit prior to hookup to indoor coil. They also contain
gage ports for measuring system pressures, and provide shut-off
convenience for certain types of repairs. (See Fig. 17.)
A88401
STAINLESS
STEEL
STEM
SERVICE
PORT
ENTRANCE
BACK
SEAT
POSITION
FRONT
SEAT
POSITION
12
FIELD SIDE
FORGED BACK SEATING VALVE
Fig. 17—Service Valve
A91435