Daikin RZQ140B7W1B [143/326] Expansion valve control at startup

Daikin RZQ71B8V3B [143/326] Expansion valve control at startup
ESIE05-03 Outdoor Unit Functional Concept
Part 2 Functional Description 2–59
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3.4.1 Expansion Valve Control at Startup
Outline Before going to the general expansion valve control, the expansion valve opening will be limited in
order to avoid the risk of liquid back and allow quick build up of pressure difference.
Details During startup, the opening degree is determined by both the compressor frequency & the suction
superheat. During startup, it is not possible to use only the value of the suction superheat because the
operation is not stable yet. As a consequence also the SH value will not be stable.
Graph
Expansion valve
opening during
pressure
equalization
On RZQ71 units (using double swing compressor) the expansion valve will be fully opened (to 480
pulses) for pressure equalisation before compressor start-up. Just before compressor start up, the
expansion valve opening will be set to 65 pulses, same as for the 100~140 class.
Ending condition The starting control will be terminated when the low pressure value < 6 bar or when the maximum
starting time of 10 minutes has been reached in case the low pressure value stays > 6 bar.
Compressor
Motorized valve
Pressure equalizing
control before
compressor start
Pressure
equalizing
start
Pressure
equalizing
complete
Starting
control
complete
Starting control
RZQ71: 73 Hz
RZQ100 & 125: 107 Hz
RZQ71: 480 pls
RZQ100~140:
65 pls
15 s
ESIE05-03.book Page 59 Wednesday, April 6, 2005 4:09 PM

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