Sinclair SCV-750EB Service Manual page 36

5.4 Compressor Step Control
The running speed of six-pole compressors in rotations per second (rps) is one third of the frequency (in Hz) of the electrical
input to the compressor motor. The frequency of the electrical input to the compressor motors can be altered at a rate of 1Hz in
two seconds.
5.5 Four-way Valve Control
The four-way valve is used to change the direction of refrigerant flow through the water side heat exchanger in order to switch
between cooling and heating operations. During heating operation, the four-way valve is on; during cooling and defrosting
operation, the four-way valve is off.
5.6 Electronic Expansion Valve Control
 Power-on self-test:
When the power is first turned on, the EXV is closed for 700 steps, proofreading the 0-step position, and re-opening at a
maximum of 480.
 Startup:
Adjust from 480 to the initial position, (the initial opening is determined by the ambient temperature), maintain for a
period of time. EXV is controlled according to suction superheat, exhaust, and compressor speed.
 When the outdoor unit is in standby:
The EXV is at position 480 (steps).
 When the outdoor unit stops:
After the compressor shuts down for 1 minute, the EXV is fully closed first, and then opened to the initial position.
5.7 Outdoor Fan Control
For SCV-750EB:
Fan speed index
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
34
Fan speed (rpm)
FAN A
0
150
190
230
270
330
150
170
190
210
230
250
270
290
310
330
350
370
400
430
450
470
510
550
580
FAN B
0
0
0
0
0
0
150
170
190
210
230
250
270
290
310
330
350
370
400
430
450
470
510
550
580