Specifications

SERVICING
192 Rev. 3
On systems using capillary tubes or flow control restrictors,
superheat is adjusted in accordance with the "DESIRED
SUPERHEAT vs. OUTDOOR TEMP" chart as explained in
section S-103 CHARGING
S-109 CHECKING SUBCOOLING
Refrigerant liquid is considered subcooled when its tempera-
ture is lower than the saturation temperature corresponding
to its pressure. The degree of subcooling equals the de-
grees of temperature decrease below the saturation tempera-
ture at the existing pressure.
1. Attach an accurate thermometer or preferably a thermo-
couple type temperature tester to the liquid line as it leaves
the condensing unit.
2. Install a high side pressure gauge on the high side (liq-
uid) service valve at the front of the unit.
3. Record the gauge pressure and the temperature of the
line.
4. Convert the liquid pressure gauge reading to temperature
by finding the gauge reading in Temperature - Pressure
Chart and reading to the left, find the temperature in the
°F. Column.
5. The difference between the thermometer reading and pres-
sure to temperature conversion is the amount of
subcooling.
EXAMPLE:
a. Liquid Line Pressure = 260
b. Corresponding Temp. °F. = 120°
c. Thermometer on Liquid line = 105°F.
To obtain the amount of subcooling subtract 105 from 120°F.
The difference is 15° subcooling. The normal subcooling range
is 14° - 18° subcooling for cooling units.
S-110 CHECKING EXPANSION VALVE OPERA-
TION
1. Remove the remote bulb of the expansion valve from the
suction line.
2. Start the system and cool the bulb in a container of ice
water, closing the valve. As you cool the bulb the suction
pressure should fall and the suction temperature will rise.
3. Next warm the bulb in your hand. As you warm the bulb
the suction pressure should rise and the suction tem-
perature will fall.
4. If a temperature or pressure change is noticed, the ex-
pansion valve is operating. If no change is noticed, the
valve is restricted, the power element is faulty, or the
equalizer tube is plugged.
5. Capture the charge, replace the valve and drier, evacuate
and recharge.
4
50 60 70 80 90 100 110 120
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
36
70 DEG ID TEMP
75 DEG ID TEMP
80 DEG ID TEMP
85 DEG ID TEMP
90 DEG ID TEMP
SUPERHEAT @ O.D. UNIT
OUTDOOR TEMPERATURE
DESIRED SUPERHEAT vs. OUTDOOR TEMP