Main Functions; Temperature Control; Frequency Principle - Daikin FTXM-V Series Service Manual

Main Functions

1. Main Functions

1.1

Temperature Control

Definitions of The definitions of temperatures are classified as following.
Temperatures
 Room temperature: temperature of lower part of the room
 Set temperature: temperature set by remote controller
 Room thermistor temperature: temperature detected by room temperature thermistor
 Target temperature: temperature determined by microcomputer
Temperature The temperature of the room is detected by the room temperature thermistor. However, there is a
Control difference between the temperature detected by room temperature thermistor and the temperature
of lower part of the room, depending on the type of the indoor unit or installation condition. In
practice, the temperature control is done by the target temperature appropriately adjusted for the
indoor unit and the temperature detected by room temperature thermistor.
1.2

Frequency Principle

Control
The frequency of the compressor is controlled by the following 2 parameters:
Parameters  The load condition of the operating indoor unit
 The difference between the room thermistor temperature and the target temperature
The target frequency is adapted by additional parameters in the following cases:
 Frequency restrictions
 Initial settings
 Forced cooling operation
Inverter Principle
To regulate the capacity, a frequency control is needed. The inverter makes it possible to control
the rotation speed of the compressor. The followings explain the inverter principle:
Phase 1
The supplied AC power source is converted into the DC power source for the present.
Phase 2
The DC power source is reconverted into the three phase AC power source with variable
frequency.
 When the frequency increases, the rotation speed of the compressor increases resulting in an
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Room temperature
increase of refrigerant circulation. This leads to a larger amount of heat exchange per unit.
Room thermistor temperature
Set temperature
SiUS042113E
Target temperature
(R12321)
Part 4 Functions and Control