Service manual
6-- 13
T--318
2
3
1
4
5
1. Suction Line
2. Thumbscrew
3. TXV Bulb Clamp
4. TX
V
Bulb
5. Foam Insulation
Figure 6-19 Thermostatic Expansion Valve Bulb
6.14.1 Checking Superheat
NOTE
Proper superheat measurement should be
completed at -18 C (0 F) container box temper-
ature where possible.
a. Open the upper right (EFM#1) access panel (see
Figure 2-1) to expose the expansion valve.
b. Attach a temperature sensor near the expansion
valve bulb and insulate. Make sure the suction line is
clean and that firm contact is made with the sensor .
c. Connect an accurate gauge to the service port direct-
ly upstream of the suction modulating valve
d. Set the temperature set point to -18 C (0 F) and run
unit until conditions stabilize.
e. The readings may cycle from a high to a low reading.
Take readings of temperature and pressure every
three to five minutes for a total of 5 or 6 readings
f. From the temperature/pressure chart (Table 6-8), de-
termine the saturation temperature corresponding to
the evaporator outlet test pressures at the suction
modulation valve.
g. Subtract the saturation temperatures determined in
step f from the temperatures measured in step e. The
difference is the superheat of the suction gas. Deter-
mine the average superheat It should be 4.5 to 6.7 C
(8 to 12 F).
6.14.2 Expansion Valve Replacement
a. Removing the Expansion Valve
NOTES
1. The TXV is a hermetic valve and does not
have adjustable superheat (See
Figure 6-20).
2. All connections on the hermetic TXV are
bi-metallic, copper on the inside and
stainless on the outside.
3. All joints on the hermetic TXV (inlet, outlet
and equalizer lines) are brazed.
4. Bi-metallic connections heat up very quickly.
1
6
5
4
3
2
1. Hermetic Thermostatic Expansion Valve
2. Non-adjustable Superheat Stem
3. Equalizer Connection
4. Inlet Connection
5. Outlet Connection
6. Hermetic Expansion Valve Bulb
Figure 6-20 Thermostatic Expansion Valve
Copper Tube
(Apply heat for
10-15 seconds)
Bi-metallic T ube Connection
(Apply heat for 2-5 seconds)
Use of a wet cloth is not neces-
sary due to rapid heat dissipation
of the bi-metallic connections
Braze Rod
(’Sil-Phos” = 5.5% Silver, 6% Phosphorus)
Figure 6-21 Hermetic Thermostatic Expansion Valve Brazing Procedure