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TABLE 10
120H Normal Operating Pressures
Outdoor Coil Entering Air Temperature
65
°
F
75
°
F
85
°
F
95
°
F
105
°
F
115
°
F
Suct
(psig)
Disc
(psig)
Suct
(psig)
Disc
(psig)
Suct
(psig)
Disc
(psig)
Suct
(psig)
Disc
(psig)
Suct
(psig)
Disc
(psig)
Suct
(psig)
Disc
(psig)
Circuit 1
113
251
113
290
112
331
116
383
117
439
120
520
120
254
123
293
124
338
126
388
127
441
129
510
139
264
142
303
144
345
147
393
146
445
148
510
155
278
160
314
164
357
167
403
169
456
173
512
Circuit 2
110
251
111
287
111
329
114
388
117
454
120
538
119
249
120
291
122
336
124
389
126
447
128
520
139
259
142
297
143
337
145
390
144
444
149
514
155
274
160
307
164
349
166
393
169
448
170
510
Suction Pressure (psig)
115°
105°
95°
85°
75°
65°
60
70
80
90
100
110
120
130
100
110
120
130
140
150
160
170
180
Liquid Temperature (
°
F)
120H Charging Curves
Circuit 1
Circuit 2
Outdoor Temperature (°F)
C-Compressor Controls
See unit wiring diagram to determine which controls are
used on each unit. Optional controls are identified on
wiring diagrams by arrows at junction points.
1- High Pressure Switches (S4, S7)
Compressor circuits are protected by a high pressure
switch which cuts out at 640 psig + 10 psig (4413 kPa
+ 70 kPa).
2- Freezestats (S49, S50)
Switches de-energize compressors when evaporator
coil temperature falls below 29°F (-2°C) to prevent
evaporator freeze-up. Switches reset when
evaporator coil temperature reaches 58°F (15°C).
3- Crankcase Heater (HR1, HR2)
Compressors have belly band compressor oil heaters
which must be on 24 hours before running
compressors. Energize by setting thermostat so that
there is no cooling demand, to prevent compressor
from cycling, and apply power to unit.
