Main Functions; Temperature Control; Frequency Principle - Daikin FTX20K(2)V1B Service Manual

Main Functions

1. Main Functions

1.1

Temperature Control

The definitions of temperatures are classified as following.
Definitions of
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
The temperature of the room is detected by the room temperature thermistor. However, there is
Temperature
a difference between the temperature detected by room temperature thermistor and the
Control
temperature of lower part of the room, depending on the type of the indoor unit or installation
condition. Practically, 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

The frequency of the compressor is controlled by the following 2 parameters:
Control
 The load condition of the operating indoor unit
Parameters
 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
To regulate the capacity, a frequency control is needed. The inverter makes it possible to
Inverter Principle
control the rotation speed of the compressor. The following table explains the conversion
principle:
15
Room temperature
Phase
The supplied AC power source is converted into the DC power source for the present.
1
The DC power source is reconverted into the three phase AC power source with variable
2
frequency.
 When the frequency increases, the rotation speed of the compressor increases resulting
in an increase of refrigerant circulation. This leads to a larger amount of heat exchange
per unit.
 When the frequency decreases, the rotation speed of the compressor decreases
resulting in a decrease of refrigerant circulation. This leads to a smaller amount of heat
exchange per unit.
Room thermistor temperature
Description
SiBE041525F
Target temperature
Set temperature
(R12321)
Functions and Control