39
4.14.1 Expansion Valve Superheat Check &
Adjustment
a.
Remove insulation from expansion valve
bulb and suction line.
b.
Loosen the TXV bulb clamp and make
sure area under clamp (above TXV bulb)
is clean.
c.
Place thermocouple above (parallel to)
the TXV bulb and then secure loosened
clamp making sure bulb and
thermometer are firmly secured to
suction line.
d.
Reinsulate bulb and thermometer
e.
Connect a low-side gauge to the port on
the Evaporator outlet
f.
Route your compound gauge hose and
thermocouple probe through the
grommet in the evaporator section. It is
located near the expansion valve inlet.
This allows you to reinstall the
evaporator panel and fan to start the
process of determining your superheat
setting
g.
Run unit until stabilized at 40F box
temperature.
h.
Maintain high side pressure according to
100F ambient temperature. This can be
simulated. by covering the condenser.
See Section 6.2 for pressure
temperature chart
i.
Reference chart 6.1 (Vapor temperature
& pressure relationships) to determine
the
saturation
temperature
corresponding to the reading from the
evaporator outlet pressure.
j.
Note the temperature of the suction gas
at the expansion valve bulb
Now that you have taken your measurements.
Convert your evaporator outlet pressure to
temperature using the Vapor temp/pressure
chart (6.1).
Using the equation below you can calculate your
superheat:
SUPERHEAT =
A
⁰
F
–
B
⁰
F
where:
A
= Equalizer line Temp in ⁰F (read from thermocouple)
and:
B
= Evaporator outlet Temp in ⁰F (converted from the
pressure reading)
Your superheat setting should equal 10⁰F ± 20%
Adjust the Superheat Setting Spindle accordingly to reach
the correct superheat.
1.
Remove Cap from Setting Spindle
(Figure 16)
2.
Clockwise Rotation increases superheat
3.
Counterclockwise Rotation decreases
superheat
Figure 22 - Equalizer line and Evaporator Outlet
Figure 23 - Superheat Test Connections
