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SERVICING
6. When brazing, sweep the tubing with dry nitrogen
to prevent the formation of oxides on the inside
surfaces.
7. Complete any repair by replacing the liquid line drier
in the system, evacuate and charge.
BRAZING MATERIALS
Copper to Copper Joints - Sil-Fos used without flux
(alloy of 15% silver, 80% copper, and 5% phosphorous).
Recommended heat 1400°F.
Copper to Steel Joints - Silver Solder used without a flux
(alloy of 30% silver, 38% copper, 32% zinc). Recommended
heat - 1200°F.
S-101 Leak Testing (nitrogen or nitrogen-traced)
WARNING
To avoid the risk of fire or explosion, never use
oxygen, high pressure air or flammable gases for leak
testing of a refrigeration system.
WARNING
To avoid possible explosion, the line from the
nitrogen cylinder must include a pressure regulator
and a pressure relief valve. The pressure relief valve
must be set to open at no more than 150 psig.
Pressure test the system using dry nitrogen and soapy
water to locate leaks. If you wish to use a leak detector,
charge the system to 10 psi using the appropriate
refrigerant then use nitrogen to finish charging the system
to working pressure, then apply the detector to suspect
areas. If leaks are found, repair them. After repair, repeat
the pressure test. If no leaks exist, proceed to system
evacuation.
58
S-102 Evacuation
WARNING
REFRIGERANT UNDER PRESSURE!
Failure to follow proper procedures may cause
property damage, personal injury or death.
This is the most important part of the entire service
procedure. The life and efficiency of the equipment
is dependent upon the thoroughness exercised by the
serviceman when evacuating air (non-condensables) and
moisture from the system.
Air in a system causes high condensing temperature and
pressure, resulting in increased power input and reduced
performance.
Moisture chemically reacts with the refrigerant oil to form
corrosive acids. These acids attack motor windings and
parts, causing breakdown.
The equipment required to thoroughly evacuate the
system is a high vacuum pump, capable of producing
a vacuum equivalent to 25 microns absolute and a
thermocouple vacuum gauge to give a true reading of the
vacuum in the system
NOTE: Never use the system compressor as a vacuum
pump or run when under a high vacuum. Motor damage
could occur.
WARNING
Do not front seat the service valve(s) with the
compressor open, with the suction line of the
comprssor closed or severely restricted.
1. Connect the vacuum pump, vacuum tight manifold
set with high vacuum hoses, thermocouple vacuum
gauge and charging cylinder.
2. Start the vacuum pump and open the shut off valve
to the high vacuum gauge manifold only. After
the compound gauge (low side) has dropped to
approximately 29 inches of vacuum, open the valve
to the vacuum thermocouple gauge. See that the
vacuum pump will blank-off to a maximum of 25
microns. A high vacuum pump can only produce a
good vacuum if its oil is non-contaminated.
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