TM 9-4120-360-14
NORMAL TEMPERATURE - RESSURE RELATIONSHIPS
95F (36C) dry bulb return air to unit
100F
75F
110F
Outdoor ambient
50F
125F
10C
24C
43.5C
temperature
38C
52C
Gauge Pressures
56-60
56-65
65-75
70-80
75-90
Suction (psig)
4.92-5.62
4.57-5.27
3.93-4.22
3.93-4.57
5.27-6.33
(Kg/Cm)
135-155
185-205
Discharge (psig)
275-295
375-380
400-420
13.00-14.41
19.33-20.74
26.36- 26.72
28.12-29.53
9.50-10.90
(Kg/Cm)
80F (27C) dry bulb return air to unit
100F
125F
50F
75F
Outdoor ambient
temperature
10C
24C
52C
38C
Gauge Pressures
56 min.
Suction (psig)
56 min.
56-65
65-75
3.93"
4.57-5.27
3.93"
3.93-4.57
(Kg/Cm)
Discharge (psig)
130-150
180-200
290-410
270-290
12.65-14.06
18.98-20.39
20.39-28.82
9.14-10.55
(Kg/Cm)
NOTE: Dry bulb temperatures are measured with an ordinary thermometer
Table 4-2. Troubleshootmg - (Cont.)
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
If pressures are too low, cheek for leaks and add refrigerant; if too high, bleed off refrigerant until pressure is
normal.
If pressures are normal, turn off power, and short-circuit high- or low-pressure cutout switch. Turn on power
Step 3.
for maximum of 12 seconds, and see whether compressor operates normally.
Do not exceed 12-second operating time, or vacuum may be formed in suction side of refrigeration
system and damage compressor.
Bleed off refrigerant over a period of 5-6 hours to prevent oil being blown out of system, then replace faulty
pressure cutout switch and recharge system.
Step 1.
Check condenser intake screen for obstructions.
Clean screen or remove obstructions.
Step 2.
Check condenser coil for dirt or obstruction.
Clean coil with vacuum cleaner, or remove obstruction.
Step 3.
Visually check to be sure that condenser fan is operating properly.
Tighten setscrews on loose impeller. Replace bad motor.
9. COMPRESSOR RUNS BUT DOES NOT COOL
Step 1.
Check sight-glass liquid indicator for bubbles indicating low charge of refrigerant. If bubbles are present, check
refrigeration system for leaks.
Discharge system over a period of' 5-6 hours to prevent oil being blown out of system, then repair leaks
or replace leaking component.
4-12