Compressor Sequencing; Pressure Curves - Trane RAUJ-C20 Installation, Operation And Maintenance Manual

S S t t a a r r t t - - U U p p
Table 36. Pressure control switch settings (psi)
Pressure Switch
Hi Pressure
Lo Pressure
Condenser Fan Cycling
switch
EVP Lo Pressure

Compressor Sequencing

Table 37. Compressor sequence: 20-120 Ton units
Control
Unit
Step
Size Circuit 1
1 1A
20
1A, 1B
2
1 1A
25
1A, 1B
2
1 1A
30
1A, 1B
2
1 1A
2 1A
40
3 1A, 1B
4 1A, 1B
1 1A
2 1A
50
3 1A, 1B
4 1A, 1B
1 1A
2 1A
60
3 1A, 1B
4 1A, 1B
1 1A
2 1A
3 1A, 1B
80
4 1A, 1B
5 1A, 1B, 1C
6 1A, 1B, 1C
114
Make Break
550 650
78 58
444 255
105 82
% Loaded
Circuit 2 Unit
— 50
— 100
— 42
— 100
— 50
— 100
- 25
2A 50
2A 75
2A, 2B 100
— 23
2A 46
2A 73
2A, 2B 100
— 25
2A 50
2A 75
2A, 2B 100
— 17
2A 33
2A 50
2A, 2B 66
2A, 2B 83
2A, 2B, 2C 100
Table 37. Compressor sequence: 20-120 Ton units
(continued)
Control
Unit
Step
Size Circuit 1
100 1 1A
2 1A
3 1A, 1B
4 1A, 1B
5 1A, 1B, 1C
6 1A, 1B, 1C
120 1 1A
2 1A
3 1A, 1B
4 1A, 1B
5 1A, 1B, 1C
6 1A, 1B, 1C

Pressure Curves

N N o o t t e 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 within +/- 10 psig of graph.
Figure 75. 20 Ton cooling cycle pressure curve
20T Cooling Cycle Pressure Curve
All compressors and condenser fans running
550
500
450
400
350
300
250
95 105 115
Suction pressure, PSIG
% Loaded
Circuit 2 Unit
— 15
2A 30
2A 45
2A, 2B 60
2A, 2B 80
2A, 2B, 2C 100
— 17
2A 33
2A 50
2A, 2B 66
2A, 2B 83
2A, 2B, 2C 100
105°F OD
95°F OD
85°F OD
75°F OD
65°F OD
125 135 145
SS-SVX11K-EN