Trane 4TVH0086FE000AA Service Manual page 47

5.2 Compressor Output Control
The compressor rotation speed is controlled according to the load requirement. Before compressor startup, the outdoor
unit first estimates the indoor unit load requirement according to the nominal capacity of indoor units currently running,
and then correct for ambient temperature. The compressors then start up according to the corrected load requirement.
During operation the compressors are controlled according to the nominal capacity of indoor units currently running and
the indoor unit heat exchanger temperatures.
5.3 Compressor Step Control
The running speed of the compressors in rotations per second (rps) is one third of the frequency (in Hz) of the electrical
input to the compressor motors. The compressor speed can be altered in increments of 1 rps.
5.4 Operating Priority and Rotation of Compressors
Figures 3-5.1 shows the compressor operating priority and rotation in the outdoor unit. In units with two compressors,
inverter compressor A (BP1) operates in priority to inverter compressor B (BP2).
Figure 3-5.1: Compressor priority and rotation – one outdoor unit
5.5 Electronic Expansion Valve Control
EXVA control
The position of electronic expansion valves EXVA is controlled in steps from 0 (fully closed) to 480 (fully open) or 3000
(fully open).
In cooling mode:
 When the outdoor unit is in standby:
 EXVA is at position 352 (steps) or 2112 (steps).
 When the outdoor unit is running:
 EXVA is controlled according to discharge temperature.
In heating mode:
 When the outdoor unit is in standby:
 EXVA is at position 352 (steps) or 2112 (steps).
 When the outdoor unit is running:
 EXVA is controlled according to discharge superheat.
EXVC control
The positions of electronic expansion valves EXVC are controlled in steps from 0 (fully closed) to 480 (fully open).
In cooling / heating mode:
No. 1
BP
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No. 1 No. 2
BP1 BP2