PREVOST X3-45 2016 Maintenance Manual Download

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Section 22: HEATING AND AIR CONDITIONING

PA1593

will break at 450 psi (3103 kPa) and relieve the
receiver tank pressure.

MAINTENANCE

Check refrigerant level and add if necessary,
every 6,250 miles (10 000 km) or twice a
year, whichever comes first.

The receiver tank incorporates an inlet valve on
the inlet side (upper section) which allows the
tank to be isolated or serviced. An outlet valve
on the outlet side (lower section) permits
complete isolation from the rest of the system.

7.6 FILTER

DRYER

A filter dryer, also located in the condenser
compartment, is installed on the liquid
refrigerant line after the receiver tank. It is used
to absorb moisture and foreign matter from
refrigerant before it reaches the expansion
valves.
The filter should be replaced if the system has
been opened or after a prolonged exposure,
when the moisture indicator sight glass turns to
pink.

7.6.1 Replacement

The filter is of the disposable type. When
replacement is required, remove and discard the
complete unit and replace with a new unit of the
same type according to this procedure:

1. Isolate

the

refrigerant

in the receiver tank by

following the “Pumping Down” procedure
explained in this section

MAINTENANCE

Check refrigerant moisture indicator every
6,250 miles (10 000 km) or twice a year,
whichever comes first. Replace filter dryer unit
according to moisture indicator

2. Change the filter dryer as a unit.

3. Add a small quantity of refrigerant R-134a to

the low side of the system. Check for leaks.
Return the system to normal operation.

CAUTION

Do not use carbon tetrachloride or similar
solvents to clean parts. Do not use steam
guns. Use mineral spirits or naphtha. All parts
should be thoroughly cleaned. Use a stiff
brush to wash dirt from grooves, holes, etc.

DANGER

Cleaning products are flammable and may
explode under certain conditions. Always
handle in a well ventilated area.

7.6.2 Moisture

Indicator

The moisture sensitive element consists of a
color changing ring which is reversible from pink
to blue and vice versa as the moisture content in
the refrigerant changes. Pink indicates a wet
refrigerant, light violet (caution) and blue
indicates a dry refrigerant.

Since temperature changes affect the solubility,
color change will also vary with the refrigerant
temperature. The above table shows the color
change for R-134a at various moisture levels
and liquid line refrigerant temperatures.

COLOR INDICATOR

TEMPERATURE

BLUE

(ppm)

LIGHT

VIOLET

(ppm)

PINK

(ppm)

75°F (24°C)

100°F (38°C)

125°F (52°C)

Below 5

Below 10

Below 15

5-15

10-30

15-45

Above 15

Above 30

Above 45

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 indicates a
shortage of refrigerant or restriction in 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,

PREVOST X3-45 2016, Maintenance Manual

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