Daikin FTKM-U Series Service Manual page 47

SiMX042215E
3.9.1 Initialization as Power Supply On
The electronic expansion valve is initialized (fully closed) when the power is turned on. Then,
the valve opening position is set and the pressure is equalized.
3.9.2 Pressure Equalizing Control
When the compressor is stopped, the pressure equalizing control is activated. The electronic
expansion valve opens and the pressure is equalized.
3.9.3 Opening Limit Control
The maximum and minimum opening of the electronic expansion valve are limited.
12/18 class
24 class
The electronic expansion valve is fully closed when cooling operation stops.
3.9.4 Starting Operation Control
The electronic expansion valve opening is controlled when the operation starts, thus preventing
superheating or liquid compression.
3.9.5 Control when the Frequency Changes
When the target discharge pipe temperature control is active, if the target frequency changes to
a specified value in a certain period of time, the target discharge pipe temperature control is
canceled and the target opening of the electronic expansion valve is changed according to the
frequency shift.
3.9.6 High Discharge Pipe Temperature Control
When the compressor is operating, if the discharge pipe temperature exceeds a certain value,
the electronic expansion valve opens and the refrigerant runs to the low pressure side.
This procedure lowers the discharge pipe temperature.
3.9.7 Target Discharge Pipe Temperature Control
The target discharge pipe temperature is obtained from the indoor and outdoor heat exchanger
temperature, and the electronic expansion valve opening is adjusted so that the actual
discharge pipe temperature becomes close to the target discharge pipe temperature. (Indirect
SH (superheating) control using the discharge pipe temperature)
The electronic expansion valve opening and the target discharge pipe temperature are adjusted
every 20 seconds. The opening degree of the electronic expansion valve is adjusted by the
following.
 Target discharge pipe temperature
 Actual discharge pipe temperature
 Previous discharge pipe temperature
Part 4 Functions and Control
Maximum opening
(pulse)
470
500
SC
(Subcooling)
Minimum opening
(pulse)
45
52
The target discharge pipe
temperature is set as to become
the target SH.
The inclination does not change
depending on the operating condition.
SH
(Superheating)
Control Specification
(R22539)
43