PREVOST H3-41 Maintenance Manual page 910

SECTION 22: HEATING AND AIR CONDITIONING
COLOR INDICATOR
BLUE
TEMPERATURE
(ppm)
75°F (24°C) 20
100°F (38°C) 35
125°F (52°C) 60
p.p.m.= parts per million (moisture content)
A moisture level of less than 15 p.p.m. for R-
134a indicated in the blue color range of the
above table is generally considered dry and
safe. A color indication of light blue to light violet
indicates the caution range of moisture level. For
positive protection, the drying of the system
should be continued until the color of the
element turns to deep blue.
The liquid refrigerant is readily visible through
the center opening of the moisture element
where the presence of bubbles or flash gas
indicates an insufficient system charge, low
head pressure, insufficient liquid sub cooling or
some form of restriction in the liquid line.
Moisture is one of the main causes of chemical
instability or contamination in air-conditioning
systems. If moisture is present, it can corrode
the valves, condenser and evaporator coils,
compressor and other components causing a
malfunction and eventual failure of the system.
Uncontrolled moisture in the system can result in
very expensive
replacements if not corrected at an early stage.
The moisture indicator
detection of moisture in the system and when
corrected by a desiccant charge, system
contamination is
36 PA1621 Maintenance Manual All Series | Revised February 2019
LIGHT
PINK
VIOLET
(ppm)
(ppm)
35 130
55 160
65 190
multiple component
permits an early
greatly minimized.
CLEAR
Normal, system OK
Temporary condition, normal when A/C
system is turned on. Wait a few minutes
for the system to stabilize.
BUBBLES, FOAMY
Low refrigerant level
Excessive pressure drop in filter-dryer
Restricted filter-dryer
MILKY, CLOUDED
Contaminated system
OIL STREAKS
Oil contamination
FIGURE 50: CONDITIONS THAT MAY BE OBSERVED IN
THE MOISTURE INDICATOR SIGHT GLASS