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5.8. Capacity Control
Capacity control shall provide chilled or condenser water temperature control by modulating the position
of the inlet guide vane 1, and VFD speed for variable speed compressor based.
If VFD OPTION is set to with VFD, when need to increase capacity, the control will first try to increase
IGV TARGET POSITION if it has not reached the travel limit, otherwise increase VFD TARGET SPEED;
when need to decrease capacity, the control will first try to decrease VFD TARGET SPEED if it has not
reached the minimum VFD speed, otherwise decrease IGV TARGET POSITION.
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Guide vane control
The control regulates the guide vane position as determined by the Capacity Control function in normal
condition and other functions in abnormal conditions which include capacity inhibit request, capacity
decrease request. The guide vane actuator is driven by guide vane target position and comparing to the
actual feedback value.. Guide vane actual position is limited to between zero and “GV1 TRAVEL LIMIT”
which is configured at “Service Configuration” menu. When chiller is shutting down or off, guide vane is
always driven to zero.
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VFD speed control
If VFD option is set to NO VFD, or compressor relay is not closed, VFD TARGET SPEED will be 0.
From compressor relay is commanded to be closed to the end of ramp loading, VFD TARGET SPEED
will be set to startup speed.
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