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appropriate for the refrigerant being serviced. Carefully track the amount of refrigerant charge
removed as this exact amount should be placed into the units when re-charging.
Repair / Component Replacement
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Desert Aire - LW Manual
If any portion of the system was at a vacuum, place dry nitrogen in the system until
atmospheric pressure is reached.
It is preferred that components are removed by heating the braze alloy to the re-melt
temperature and mechanically moving the component. When this is not possible due
to proximity of cabinet structure or other components, a tubing cutter can be used to
remove sections of piping. Where new tube is required for replacement, use
dehydrated tube where possible. Use the same type of fittings as original. Route the
pipe in the exact manner as originally routed.
Use Type K per ASTM B 88 or ASTM B 819 or Type ACR per ASTM B 280 copper
tubing or for all tubes 1 1/8" and smaller.
Tubes 1 3/8" and larger shall use Type K per ASTM B 88 or ASTM B 819.
Cap sections of tube and components that are not actively being installed to prevent
infiltration of moisture and contaminants.
Use only braze alloy to join tube.
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The section of filler metals is highly dependent on the tube fit, clearance, and
operator preference for flow. When flux is to be used, care should be taken
to ensure that the flux is not introduced to the inside of the tube. It is
recommended that phosphorous bearing alloys be considered for copper to
copper connections due to their self-fluxing on copper to copper joints. Refer
to alloy manufacturer's guidelines to details on compatibility.
Flow nitrogen into tubing to prevent the formation of copper oxides.
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Copper oxides form rapidly when copper is heated to temperatures required
by the brazing process and exposed to oxygen in the air. Copper oxides
flake easily on the inside of the tubing and dislodge easily when the system
is filled with refrigerant and oil. The particulate can move throughout the
system and cause contamination on valves and other critical components.
System filters may become fouled.
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Flowing nitrogen into the system and ensuring that the inside of the tube is
significantly free from oxygen while brazing ensures that oxides do not form. As the
last joints of a system are made, additional thought must be made on the location
where the nitrogen can escape. Schrader valves are placed throughout the system.
These valves can be opened to allow for nitrogen to flow without generating pressure
behind the braze joint that is being created.
See Section 5.1.1 for special procedures related to compressor replacements.
Replace liquid line filter dryer as last step in system repair. Note that the dryer will readily
absorb moisture from the ambient air and must be open only for as long as required for
installation.
After completion of all repairs, pressure test system using nitrogen pressure decay test or
nitrogen with tracer gas and appropriate leak detector.
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