Hitachi P-N23NA2 Service Manual

5 Control system
Indoor electronic expansion valve control
SMGB0099 rev.0 - 12/2016
198
5.11 Indoor electronic expansion valve control
1 After supplying power, the electronic expansion valve closes
fully before starting to open.
2 When the compressor stops, the electronic expansion valve
closes fully to set its opening.
3 When it starts (the compressor is activated), the electronic
expansion valve opens to a specic degree during cooling
operation, 1 minute.
4 During heating operation, the electronic expansion valve
opens to a specic degree.
5 During defrost, the electronic expansion valve opens to a
specic degree, as indicated in the graph.
6 Normal opening of the electronic expansion valve.
Time chart
Defrost
Heating
Opening of
electronic
expansion
valve (pulse)
Depending on
thermistor temperature
of compressor
30 sec.
Cooling operation
1 Superheat temperature setting required:
a. Heat exchanger SH:
 3 HP => SH = 0 ºC
 4 HP=> SH = -4 ºC
b. Heat exchanger SH = Tg - TL
Where,
 Tg: Indoor gas pipe temperature.
 TL: Indoor liquid pipe temperature.
 SH: Superheat.
2 Simulated PI control for the electronic expansion valve. the opening of this valve is controlled so that the SH
temperature of the heat exchanger can reach the set temperature.
Heating operation
1 Denition of the set temperature:
a. Heat exchanger SH=Ti < TL < 45 + 0.5 x Ta
Where,
 TL: Indoor liquid pipe temperature.
 Ti: Indoor air inlet temperature.
 Ta: Outdoor temperature.
2 Simulated PI control for the electronic expansion valve. The opening of the electronic expansion valve is controlled so
that the temperature of the indoor liquid pipe can reach the set temperature.

Hitachi P-N23NA2 Specifications

General

Brand	Hitachi
Model	P-N23NA2
Category	Air Conditioner
Language	English