Service manual
SERVICING
39
EXAMPLE:
a. Discharge Pressure = 260
b. Corresponding Temp. °F. = 120°
c. Thermometer on Liquid line = 109°F.
To obtain the amount of subcooling subtract 109°F from
120°F.
The difference is 11° subcooling. The normal subcooling
range is 9° - 13° subcooling for heat pumps units, 14° - 18°
for cooling units and gas packs.
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 suc-
tion 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
temperature will fall.
4. If a temperature or pressure change is notices, 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. Remove the charge, replace the valve and drier, evacu-
ate and recharge.
S-111 FIXED ORIFICE RESTRICTION DEVICES
The fixed orifice restriction device (flowrator) used in con-
junction with the indoor and outdoor coils are a predeter-
mined bore (I.D.).
It is designed to control the rate of liquid refrigerant flow
into an evaporator coil.
The amount of refrigerant that flows through the fixed ori-
fice restriction device is regulated by the pressure differ-
ence between the high and low sides of the system.
In the cooling cycle when the outdoor air temperature rises,
the high side condensing pressure rises. At the same time,
the cooling load on the indoor coil increases, causing the
low side pressure to rise, but at a slower rate.
Since the high side pressure rises faster when the tem-
perature increases, more refrigerant flows to the evapora-
tor, increasing the cooling capacity of the system.
When the outdoor temperature falls, the reverse takes place.
The condensing pressure falls, and the cooling loads on
the indoor coil decreases, causing less refrigerant flow.
A strainer is placed on the entering side of the tube to pre-
vent any foreign material from becoming lodged inside the
fixed orifice restriction device.
If a restriction should become evident, proceed as follows:
1. Recover refrigerant charge.
2. Remove the orifice or tube strainer assembly and re-
place.
3. Replace liquid line drier, evacuate and recharge.
TEMPERATURE - PRESSURE (R-22)
Temp.
°F.
Gauge Pressure
(PSIG) Freon-22
Temp.
°F.
Gauge Pressure
(PSIG) Freon-22
-40
-38
-36
-34
0.61
1.42
2.27
3.15
60
62
64
65
102.5
106.3
110.2
114.2
-32
-30
-28
-26
4.07
5.02
6.01
7.03
68
70
72
74
118.3
122.5
126.8
131.2
-24
-22
-20
-18
8.09
9.18
10.31
11.48
76
78
80
82
135.7
140.5
145.0
149.5
-16
-14
-12
-10
12.61
13.94
15.24
16.59
84
86
88
90
154.7
159.8
164.9
170.1
-8
-6
-4
-2
17.99
19.44
20.94
22.49
92
94
96
96
175.4
180.9
186.5
192.1
0
2
4
6
24.09
25.73
27.44
29.21
100
102
104
106
197.9
203.8
209.9
216.0
8
10
12
14
31.04
32.93
34.88
36.89
108
110
112
114
222.3
228.7
235.2
241.9
16
18
20
22
38.96
41.09
43.28
45.53
116
118
120
122
248.7
255.6
262.6
269.7
24
26
28
30
47.85
50.24
52.70
55.23
124
126
128
130
276.9
284.1
291.4
298.8
32
34
36
38
57.83
60.51
63.27
66.11
132
134
136
136
306.3
314.0
321.9
329.9
40
42
44
46
69.02
71.99
75.04
78.18
140
142
144
146
338.0
346.3
355.0
364.3
48
50
52
54
81.40
84.70
88.10
91.5
158
150
152
154
374.1
384.3
392.3
401.3
56
58
95.1
98.8
156
158
160
411.3
421.8
433.3