Normal Control
SiME332106E
56
Part 4 Functions and 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
(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.
Heating: discharge pressure sensor value is converted into condensing saturation
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.
The initial target saturated temperature can be changed. For details refer to
Details of
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.
During operation, outdoor control will take into account the pressure drop so that at indoor
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).
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
temperature and a set temperature after startup period.
