11-1
CONTROL SYSTEM
SM PNXADCI 1-A.1 GB
11.1 General Functions and Operating Rules
The DCI software is fully parametric.
All the model dependent parameters are shown in Blue color and with Italic style [parameter].
The parameters values are given in the last section of this control logic chapter of the service
manual.
11.1.1 System Operation Concept
The control function is divided between indoor and outdoor unit controllers. Indoor unit is the
System ‘Master’, requesting the outdoor unit for cooling/heating capacity supply. The outdoor unit is
edomnoitcetorpaotnisretnetisselnmetsyseht 'Slave’ and it must supply the required capacity
avoiding it from supplying the requested capacity.
The capacity request is transferred via indoor to outdoor communication, and is represented by a
parameter called ‘NLOAD’. NLOAD is an integer number with values between 0 and 127, and it
represents the heat or cool load felt by the indoor unit.
11.1.2 Compressor Frequency Control
11.1.2.1 NLOAD setting
The NLOAD setting is done by the indoor unit controller, based on a PI control scheme.
The actual NLOAD to be sent to the outdoor unit controller is based on the preliminary LOAD
calculation, the indoor fan speed, and the power shedding function.
NLOAD limits as a function of indoor fan speed:
Indoor Fan Speed Maximum NLOAD Cooling Maximum NLOAD Heating
Low
Max NLOADIF1C
127
Medium
Max NLOADIF2C
127
High
Max NLOADIF3C
127
Turbo
Max NLOADIF4C
127
Auto
Max NLOADIF5C
127
NLOAD limits as a function of power shedding:
Mode Power Shedding OFF Power Shedding ON
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11.1.3 Target Frequency Setting
The compressor target frequency is a function of the NLOAD number sent from the indoor
controller and the outdoor air temperature.
Basic Target Frequency Setting:
NLOAD Target Frequency
127
Maximum frequency
10 < NLOAD < 127 Interpolated value between minimum and maximum frequency
10
Minimum frequency
0 Compressor is stopped
11. CONTROL SYSTEM for PNXA 9 / 12
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