Compressor Capacity Control - Daikin VRV RXYMQ-A Series Service Manual

Normal Control
5.3

Compressor Capacity Control

Tc : High pressure equivalent saturation temperature
Te : Low pressure equivalent saturation temperature
Capacity steps
The compressor rotation speed is changed according to the control pressure.
 Cooling: suction pressure sensor value is converted into evaporation saturated temperature
 Heating: discharge pressure sensor value is converted into condensing saturation
 The initial target saturated temperature can be changed. For details refer to Details of
 During operation, outdoor control will take into account the pressure drop so that at indoor
 Target Te outdoor (cooling) = Te set – estimated pressure drop – A.
 Target Tc outdoor (heating) = Tc set + estimated pressure drop + A.
 Correction factor A depends on the absolute value of the difference between indoor air inlet
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(relation between pressure and evaporating temperature based on characteristics of
refrigerant R-410A). For detailed explanation refer to chapter field settings (Details of
Setting Mode (Mode 2) on page 122 and installation manual outdoor chapter Energy saving
and optimum operation).
 Initial selection is made between Automatic, Fixed or High sensible.
 During operation, the outdoor target evaporating temperature can be changed based on
the selected sub function, taking indoor load into account.
temperature.
 Initial selection is made between Automatic, Fixed, or High sensible.
 During operation, the outdoor target condensing temperature can be changed based on
the selected sub function, taking indoor load into account.
Setting Mode (Mode 2) on page 122 for Cooling: Te set based on field setting 2-8, for
heating: Tc set based on field setting 2-9.
units, the preset target temperature is reached (average). The estimated pressure drop is
calculated based on:
 Pressure drop characteristics found during test-operation outdoor (step 7). At several
evaporating temperatures, outdoor control stores difference between outdoor
evaporating temperature and average of indoor heat exchanger (indoor evaporating
temperature).
 To have judgment of gas speed in main suction pipe, control takes the capacity step of
the outdoor unit into account. In function of pressure drop characteristics at the different
compressor capacity steps, control concludes the category of system pipe lay out (long,
medium, short).
temperature and a set temperature after startup period.
SiME332106E
Part 4 Functions and Control