Expansion Valve Regulating Functions; Expansion Valve Control At Startup - Daikin SkyAir Service Manual

Expansion Valve Regulating Functions

5. Expansion Valve Regulating Functions

5.1

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 On RZQ71, RZQS71·100 units (using double swing compressor) the expansion valve will be
fully opened (to 480 pulses) for pressure equalisation before compressor start-up. Just before
opening during
compressor start up, the expansion valve opening will be set to 65 pulses, same as for the
pressure
RZQ100~140 class.
equalization
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.
78
RZQ71~140C7, RZQS71~140C7V1B
Compressor
Electronic
expansion valve
Pressure
Pressure
equalizing
equalizing
complete
start
Pressure equalizing
control before
compressor start
Cooling or
Heating(<25˚ C)
65 pls
Heating(>25˚ C)
480 pls
SiBE28-804
Starting
control
complete
Starting
control
112Hz
Functional Description