Trane RAUJ-C20, Installation, Operation And Maintenance Manual

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114 SS-SVX11K-EN
Table 36. Pressure control switch settings (psi)
Pressure Switch Make Break
Hi Pressure 550 650
Lo Pressure 78 58
Condenser Fan Cycling
switch
444 255
EVP Lo Pressure 105 82
Compressor Sequencing
Table 37. Compressor sequence: 20-120 Ton units
Unit
Size
Control
Step
Circuit 1 Circuit 2
% Loaded
Unit
20
1 1A — 50
2
1A, 1B
— 100
25
1 1A — 42
2
1A, 1B
— 100
30
1 1A — 50
2
1A, 1B
— 100
40
1 1A - 25
2 1A 2A 50
3 1A, 1B 2A 75
4 1A, 1B 2A, 2B 100
50
1 1A — 23
2 1A 2A 46
3 1A, 1B 2A 73
4 1A, 1B 2A, 2B 100
60
1 1A — 25
2 1A 2A 50
3 1A, 1B 2A 75
4 1A, 1B 2A, 2B 100
80
1 1A — 17
2 1A 2A 33
3 1A, 1B 2A 50
4 1A, 1B 2A, 2B 66
5 1A, 1B, 1C 2A, 2B 83
6 1A, 1B, 1C 2A, 2B, 2C 100
Table 37. Compressor sequence: 20-120 Ton units
(continued)
Unit
Size
Control
Step
Circuit 1 Circuit 2
% Loaded
Unit
100 1 1A — 15
2 1A 2A 30
3 1A, 1B 2A 45
4 1A, 1B 2A, 2B 60
5 1A, 1B, 1C 2A, 2B 80
6 1A, 1B, 1C 2A, 2B, 2C 100
120 1 1A — 17
2 1A 2A 33
3 1A, 1B 2A 50
4 1A, 1B 2A, 2B 66
5 1A, 1B, 1C 2A, 2B 83
6 1A, 1B, 1C 2A, 2B, 2C 100
Pressure Curves
N No otte e:: For the following curves, all compressors and
condenser fans are running.
To check operating pressures:
1. Start the unit and allow the pressures to stabilize.
2. Measure the outdoor air dry bulb temperature (F)
entering the condenser coil.
3. Measure the discharge and suction pressure (psig)
next to the compressor.
4. Plot the outdoor dry bulb temperature and the
operating suction pressure (psig) onto the chart.
5. At point of intersection, read to the left for
discharge pressure. Measured discharge pressure
should be /- 10 psig of graph.
Figure 75. 20 Ton cooling cycle pressure curve
105°F OD
95°F OD
85°F OD
75°F OD
65°F OD
Suction pressure, PSIG
95 105 115 125 135 145
250
300
350
400
450
500
550
Discha
rge
p
r
essure
,
P
S
IG
20T Cooling Cycle Pressure Curve
All compressors and condenser fans running
S Stta arrtt--U Up p