MODEL PCA090480WH
CHAPTER 2
SERVICE
Section 3: Refrigeration Basics and Service
2-3
March 2013
Page 38
Proprietary/Confidential
© 2013 Twist, Inc.
2. Fundamentals
A.
Cleanliness
of
the
refrigeration system
Absolute cleanliness is necessary in a refrigeration system in order to
insure reliable and trouble-free operation.
Vapor cycle refrigeration systems are vulnerable to attack from two
common contaminants: air and moisture, which are not readily apparent
in the system. If either or both are present in a system, they quickly join
together in attacking the refrigerant and oil, causing corrosion, copper
plating, acid formation, sludge, and other problems. When opening a
refrigeration system for repair or component replacement, take extreme
care to cover or cap open joints to prevent moisture from entering in the
form of vapor, which is always contained in the outside air.
When copper tubing and fittings are brazed, copper oxide may form on
the inside of the tube unless nitrogen or dry CO
2
is circulated through
the tubing during the brazing operation. This oxide may become a
powdered abrasive, plugging oil passages, scoring bearings, plugging
refrigerant passages, plugging filters, and causing other problems.
Taking reasonable care during service will keep contamination in a
system at a safe and acceptable level.
Important rules of cleanliness:
Keep tubing clean and dry.
Pass an inert gas through the tubing when brazing.
Keep foreign materials out of the system when it is opened.
Thoroughly evacuate the system after any exposure to the
atmosphere.
Any time the system is to be opened, introduce a slightly positive
pressure to prevent air from rushing into the lines.
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