Electronic Expansion Valve Pi Control; Step Control Of Outdoor Unit Fans - Daikin RXYQ5-48MAY1 Service Manual

Si39-407
2.3

Electronic Expansion Valve PI Control

Main Motorized Valve EV1 Control
Carries out the motorized valve (Y1E) PI control to maintain the evaporator outlet superheated
degree (SH) at constant during heating operation to make maximum use of the outdoor unit
heat exchanger (evaporator).
SH = Ts - Te
The optimum initial value of the evaporator outlet superheated degree is 5°C, but varies
depending on the discharge pipe superheated degree of inverter compressor.
Subcooling Motorized Valve EV2 Control
Makes PI control of the motorized valve (Y2E) to keep the superheated degree of the outlet gas
pipe on the evaporator side for the full use of the subcooling heat exchanger.
SH = Tsh -Te
2.4

Step Control of Outdoor Unit Fans

Used to control the revolutions of outdoor unit fans in the steps listed in table below, according to condition changes.
STEP
No.
RXYQ5MA
0 0
1 300
2 320
3 350
4 385
5 470
6 585
7 800
8 840
* Figures listed above are all those controlled while in standard mode, which vary when the system is set to high static
pressure or capacity priority mode.
Function
Fan revolutions (rpm)
RXYQ8MA RXYQ10MA
0 0
300 300
320 320
345 345
385 385
465 465
575 575
765 785
825 825
SH : Evaporator outlet superheated degree (°C)
Ts : Suction pipe temperature detected by thermistor
R2T (°C)
Te : Low pressure equivalent saturation temperature
(°C)
SH : Outlet superheated degree of evaporator (°C)
Tsh : Suction pipe temperature detected with the
thermistor R5T (°C)
Te : Low pressure equivalent saturation temperature
(°C)
RXYQ12MA RXYQ14MA
0 0
300 300
325 325
355 355
400 400
500 500
605 605
880 880
920 920
Basic Control
RXYQ16MA
0
300
325
355
400
500
605
880
920
83