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PKG-SVX029A-EN
the refrigerant/nitrogen mixture, break connections and
make repairs. Retest for leaks.
6. Confirm all service valves are open.
Brazing Procedures
WARNING
Explosion Hazard and Deadly Gases!
Failure to follow all proper safe refrigerant handling
practices could result in death or serious injury.
Never solder, braze or weld on refrigerant lines or any
unit components that are above atmospheric
pressure or where refrigerant may be present. Always
remove refrigerant by following the guidelines
established by the EPA Federal Clean Air Act or other
state or local codes as appropriate. After refrigerant
removal, use dry nitrogen to bring system back to
atmospheric pressure before opening system for
repairs. Mixtures of refrigerants and air under
pressure may become combustible in the presence of
an ignition source leading to an explosion. Excessive
heat from soldering, brazing or welding with
refrigerant vapors present can form highly toxic
gases and extremely corrosive acids.
Proper brazing techniques are essential when installing
refrigerant piping. The following factors should be kept in
mind when forming sweat connections:
1. When heating copper in the presence of air, copper
oxide forms. To prevent copper oxide from forming
inside the tubing during brazing, sweep an inert gas,
such as dry nitrogen, through the tubing. A nitrogen
flow of 1 to 3 cubic feet per minute is sufficient to
displace the air in the tubing and prevent oxidation of
the interior surfaces. Use a pressure regulating valve or
flow meter to control the flow.
2. Confirm the tubing surfaces requiring brazing are clean,
and that the tube ends are carefully reamed to remove
any burrs.
3. Confirm the inner and outer tubes of the joint are
symmetrical and have a close clearance, providing an
easy slip fit. If the joint is too loose, the connection
tensile strength is significantly reduced. Confirm the
overlap distance is equal to the inner tube diameter.
4. Wrap each refrigerant line component with a wet cloth
to keep it cool during brazing. Excessive heat can
damage the internal components.
Note: Use 40-45% silver brazing alloy (BAg-7 or BAg-
28) on dissimilar metals. Use BCup-6 brazing
alloy on copper-to-copper joints.
5. If using flux, apply it sparingly to the joint. Excess flux
will contaminate the refrigerant system.
6. Apply heat evenly over the length and circumference of
the joint.
7. Begin brazing when the joint is hot enough to melt the
brazing rod. The hot copper tubing, not the flame,
should melt the rod.
8. Continue to apply heat evenly around the joint
circumference until the brazing material is drawn into
the joint by capillary action, making a mechanically
sound and gas-tight connection.
9. Visually inspect the connection after brazing to locate
any pinholes or crevices in the joint. Use a mirror if joint
locations are difficult to see.
System Evacuation Procedures
• Each refrigeration circuit must be evacuated before the
unit can be charged and started.
• Use a rotary type vacuum pump capable of pulling a
vacuum of 100 microns or less.
• Verify that the unit disconnect switch and the system
control circuit switches are OFF.
• Oil in the vacuum pump should be changed each time
the pump is used with high quality vacuum pump oil.
Before using any oil, check the oil container for
discoloration, which usually indicates moisture in the oil
and/or water droplets. Moisture in the oil adds to what
the pump has to remove from the system, making the
pump inefficient.
• When connecting vacuum pump to refrigeration
system, it is important to manifold vacuum pump to
both high and low side of system (liquid line access
valve and suction line access valve). Follow pump
manufacturer’s directions for proper methods of using
vacuum pump.
• Lines used to connect the pump to the system should
be copper and of the largest diameter that can
practically be used. Using larger line sizes with
minimum flow resistance can significantly reduce
evacuation time.
• Rubber or synthetic hoses are not recommended for
system evacuation. They have moisture absorbing
characteristics that result in excessive rates of
evaporation, causing pressure rise during standing
vacuum test. This makes it impossible to determine if
system has a leak, excessive residual moisture, or
continual or high rate of pressure increase due to
hoses.
• Install an electronic micron vacuum gauge in the
common line ahead of the vacuum pump shutoff valve,
as shown in Figure 22, p. 47. Close valves B and C,
and open Valve A.
• Start vacuum pump. After several minutes the gauge
reading will indicate the maximum vacuum the pump is
capable of pulling. Rotary pumps should produce
vacuums of 100 microns or less.
Maintenance
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