Page 14
504953M 03/06
Charge Using the Subcooling Method –
Outdoor Temperature < 65°F (18°C)
When the outdoor ambient temperature is below 65°F
(18°C), use the subcooling method to charge the unit. Val-
ues from (table 6) are used for this procedure.
Table 6
HFC−410A Temperature (°F) − Pressure (Psig)
°F
Psig
°F
Psig
°F
Psig
°F
Psig
32
100.8
63
178.5
94
290.8
125
445.9
33
102.9
64
181.6
95
295.1
126
451.8
34
105.0
65
184.3
96
299.4
127
457.6
35
107.1
66
187.7
97
303.8
128
463.5
36
109.2
67
190.9
98
308.2
129
469.5
37
111.4
68
194.1
99
312.7
130
475.6
38
113.6
69
197.3
100
317.2
131
481.6
39
115.8
70
200.6
101
321.8
132
487.8
40
118.0
71
203.9
102
326.4
133
494.0
41
120.3
72
207.2
103
331.0
134
500.2
42
122.6
73
210.6
104
335.7
135
506.5
43
125.0
74
214.0
105
340.5
136
512.9
44
127.3
75
217.4
106
345.3
137
519.3
45
129.7
76
220.9
107
350.1
138
525.8
46
132.2
77
224.4
108
355.0
139
532.4
47
134.6
78
228.0
109
360.0
140
539.0
48
137.1
79
231.6
110
365.0
141
545.6
49
139.6
80
235.3
111
370.0
142
552.3
50
142.2
81
239.0
112
375.1
143
559.1
51
144.8
82
242.7
113
380.2
144
565.9
52
147.4
83
246.5
114
385.4
145
572.8
53
150.1
84
250.3
115
390.7
146
579.8
54
152.8
85
254.1
116
396.0
147
586.8
55
155.5
86
258.0
117
401.3
148
593.8
56
158.2
87
262.0
118
406.7
149
601.0
57
161.0
88
266.0
119
412.2
150
608.1
58
163.9
89
270.0
120
417.7
151
615.4
59
166.7
90
274.1
121
423.2
152
622.7
60
169.6
91
278.2
122
428.8
153
630.1
61
172.6
92
282.3
123
434.5
154
637.5
62
175.4
93
286.5
124
440.2
155
645.0
If necessary, restrict air flow through the outdoor coil to
achieve pressures in the 325−375 psig (2240−2585 kPa)
range. Higher pressures are necessary for checking the
charge. Block equal sections of air intake panels and move
obstructions sideways until the liquid pressure is in the
325−375 psig (2240−2585 kPa) range. See figure 13.
Blocking Outdoor Coil
*Outdoor coil should be blocked one
side at a time with cardboard or plastic
sheet until proper testing pressures
are reached.
cardboard or plastic sheet
*Four−sided unit shown.
Figure 13
1. With the manifold gauge hose still on the liquid service
port and the unit operating stably, use a digital ther-
mometer to record the liquid line temperature.
2. At the same time, record the liquid line pressure reading.
3. Use the temperature/pressure chart (table 6) to deter-
mine the saturation temperature for the liquid line
pressure reading.
4. Subtract the liquid line temperature from the saturation
temperature (according to the chart) to determine sub-
cooling.
(Saturation temperature − Liquid line tem-
perature = Subcooling)
5. Compare the subcooling value with those in table 7. If
subcooling is greater than shown, recover some refrig-
erant. If subcooling is less than shown, add some re-
frigerant. Be aware of the HFC−410A refrigerant cylin-
der. It will be light maroon−colored. Refrigerant should
be added through the vapor line valve in the liquid
state.
Table 7
Subcooling Values
Model Number
Second Stage (High Capacity) Satura-
tion Temp. − Liquid Line Temp.
°
F (
°
C)
HSXA16−024
10 + 1 (5.6 + .5)
HSXA16−036
10 + 1 (5.6 + .5)
HSXA16−048
10 + 1 (5.6 + .5)
HSXA16−060
7 + 1 (3.9 + .5)
System Operation
The outdoor unit and indoor blower cycle on demand from
the room thermostat. When the thermostat blower switch
is in the
ON
position, the indoor blower operates continu-
ously.
Two−Stage Compressor
The two−stage scroll compressor operates much like the
standard scroll compressor. The two−stage compressor
steps between low capacity and high capacity as required
to meet cooling demand. The steps occur when gas is by-
passed through a vent port in the first suction pocket. This
bypassing of gas allows the compressor to operate at low
capacity if thermostat demand allows, creating a more cost
effective and efficient compressor.
Full capacity is achieved by blocking the vent port with a
slider ring. The slider ring (vent port cover) is controlled by
a
24VDC
internal solenoid in the open position allowing low
capacity. When energized the internal solenoid closes the
slider ring, blocking the vent port and bringing the com-
pressor to full capacity. Stepping can occur during a single
thermostat demand as the motor runs continuously while
the compressor steps from low to full capacity.
Filter Drier
A filter drier is factory−installed in each HSXA16 unit to en-
sure a clean, moisture−free system. A replacement drier is
available from Lennox. Refer to Lennox Repair Part Pro-
gram.
