CONTROL SYSTEM
SM PNXADCI 1-A.1 GB
12-1
12. CONTROL SYSTEM FOR PNXA 18/21/24
12.1 Electronic Control
12.1.1 General Functions and Operating Rules (for single split models)
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.
12.1.2 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 the
system ‘Slave’ and it must supply the required capacity unless it enters into a protection mode
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.
12.1.3 Compressor Frequency Control
12.1.3.1 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
12.1.3.2 Target Frequency Setting
The compressor target frequency is set by the following table, according to the NLOAD number
received from the indoor unit.
NLOAD Target Frequency [Hz]
0 0
0 < NLOAD ≤
MinFreq
MinFreq
>MinFreq
MinFreqMinFreq}ne)LoadDeadZo(NLOAD,{min
MinFreqneLoadDeadZo
MinFreqMaxFreq
+−⋅
−
−
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