Valve Replacement; Superheat Measurement - Carrier AC310 Operation And Service Instructions Manual

1.
Figure 5- -13 Thermostatic Expansion Valve
1.. Power Head
Assembly
2.. Equalizer Connection
3.. Bulb

5.16.1 Valve Replacement

a. If compressor is operative perform low side pump
down to replace expansion valve. (refer to 5.5.1) If
compressor is inoperative recover and recycle refrig-
erant from the system.(refer to 5.5.2)
b. Remove insulation from expansion valve bulb. (See
Figure 5--13 and Figure 5--14.)
c. Loosen retaining straps holding bulb to suction line
and detach bulb from the suction line.
d. Loosen flare nuts on equalizer line and disconnect
equalizer line from the expansion valve.
e. Check, clean and remove any foreign material from
the valve body, valve seat and mating surfaces. If re-
quired, replace valve body.
NOTE
R--134a valves are adjustable. Valves are pre-
set at the factory.
f. Leak check the new valve and evacuate and dehy-
drate the system. (Refer to paragraph 5.7.)
g. 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. Ensure that retaining
straps are tight and renew insulation.
h. Fasten equalizer line to the expansion valve.
i. Evacuate and recharge the system.
j. Run the coach for approximately 30 minutes on fast
idle.
k.Check refrigerant charge. (Refer to 5.8.1)

5.16.2 Superheat Measurement

NOTE
All readings must be taken from the TXV bulb
location and out of the direct air stream.
04/08
2.
3.
4.
5.
4.
6.
7.
4.. Gasket
5.. Cage Assembly
6.. Body Flange
7.. Cap screw
3.
2.
1.
Figure 5- -14 Thermostatic Expansion Valve Bulb
and Thermocouple
1.. Suction Line
(section view)
2.. TXV Bulb Clamp
3.. Nut & Bolt (clamp)
a. Open top cover.
b. Remove Presstite insulation from expansion valve
bulb and suction line.
c. Loosen one TXV bulb clamp and make sure area un-
der clamp is clean.
d. Place temperature thermocouple in contact with the
suction tube and parallel to the TXV bulb, and then
secure loosened clamp making sure both bulb and
thermocouple are firmly secured to suction line. (See
Figure 5--14). Reinstall insulation around the bulb.
e. Connect an accurate low pressure gauge to the low
pressure port.
f. Close top cover being careful to route thermocouple
sensing wire and gauge hose outside the unit.
g. Start bus and run on fast idle until unit has stabilized,
about 20 to 30 minutes.
When conducting this test, the suction pressure
must be at least 6 psig (0.41 bar) below the ex-
pansion valve maximum operating pressure
(MOP). Refer to paragraph 1.3 for MOP.
h. From the temperature/pressure chart, determine the
saturation temperature corresponding to the evapo-
rator outlet pressure.
i. Note the temperature of the suction gas at the expan-
sion valve bulb. Subtract the saturation temperature
from this temperature. The difference is the super-
heat of the suction gas.
5--9
4.
4.. Thermocouple
5.. TXV Bulb (Shown
in the 4'clock
position)
NOTE
T-304
5.