Filter-Drier; Thermostatic Expansion Valve - Carrier CAPRI-280 Operation And Service Manual

4.10 FILTER-DRIER

a. To Check Filter Drier
Check for a restricted or plugged filter-drier by feeling
the liquid line inlet and outlet connections of the
filter-drier. If the outlet side feels cooler than the inlet
side, then the filter-drier should be changed.
b. To Replace Filter Drier
1. Pump down the unit. (Refer to section 4.4.)
2. Replace filter-drier, ensuring that the arrow points in
the direction of the refrigerant flow.
3. Drier can be evacuated at liquid service valve. (See
Figure 4-3.)
4. Check refrigerant level. (Refer to section 4.7.1.)

4.11 THERMOSTATIC EXPANSION VALVE

The thermostat expansion valve (TXV) is an automatic
device which maintains constant superheat of the
refrigerant gas leaving the evaporator regardless of
suction pressure. The valve functions are: (a) automatic
response of refrigerant flow to match the evaporator load
and (b) prevention of liquid refrigerant entering the
compressor. Unless the valve is defective, it seldom
requires any maintenance.
a. Replacing the Expansion Valve (See Figure 4-5.)
1. Pump down low side of the unit. (Refer to section
4.4.)
2. Remove insulation (Presstite) from expansion valve
bulb.
3. Loosen retaining straps holding bulb to suction line
and detach bulb from the suction line.
4. Loosen flare nuts on equalizer line and disconnect
equalizer line from the expansion valve.
5. Remove capscrews and lift off power head and cage
assemblies and gaskets.
6. Check, clean and remove any foreign material from
the valve body, valve seat and mating surfaces.
NOTE
Do not adjust the new replacement expansion
valve. Valves are preset at the factory.
7. Using new gaskets, install new cage and power head
assemblies provided with repair kit.
8. The thermal bulb is installed below the center of the
suction line (four or eight o'clock position). This area
must be clean to ensure positive bulb contact. Strap
thermal bulb to suction line and insulate both with
"Presstite." Ensure that retaining straps are tight.
(See Figure 4-6.)
9. Fasten equalizer line to the expansion valve.
10. Evacuate and dehydrate. (Refer to section 4-6.)
11. Open filter-drier inlet valve (liquid line service valve)
and all service valves.
12. Run the coach for approximately 30 minutes on fast
idle.
13. Check refrigerant level. (Refer to section 4.7.1.)
14. Check superheat. (Refer to section 4.11.b.)
1
4
3
2
1. Power Head Assembly
2. Cap Seal
3. Flare Seal
4. Retaining Nut
5. Adjusting Stem
6. Equalizer Connection
Figure 4-4. Thermostatic Expansion Valve
3
2
1
1. Suction Line (end view)
2. TXV Bulb Clamp
3. Nut and Bolt (clamp)
4. Thermocouple
5. TXV Bulb (Shown in the
4'clock position)
Figure 4-5. Thermostatic Expansion Valve
Bulb and Thermocouple
Monitor the superheat over a five minute period and
record the maximum and minimum readings. Add the
maximum and minimum readings and divide by two to
determine the superheat. The superheat should be 10F
to 12F.
b. To Check/Measure Superheat
All readings must be taken from the suction side
area of the evaporator near the TXV and out of
the direct air stream.
1. Remove filter access door.
2. Remove Presstite insulation from expansion valve
bulb and suction line.
4-5
6
7
8
5
9
8
10
11
7. Bulb
8 Gasket
9. Cage Assembly
10. Body Flange
11. Capscrew
4
5
NOTE
T-283