Daikin RXYQ-TA Series, Service Manual

Page: 83 / 337

SiUS341615E Special Control
Functions and Control 70
7.4 Defrost Operation
To defrost the outdoor heat exchanger while in evaporator, the defrost operation is conducted to recover the
heating capacity.
Tc : High pressure equivalent saturation temperature
Te : Low pressure equivalent saturation temperature
Starting conditions
Referring to the set conditions for the following items, start the defrost operation.
• Heat transfer coefficient of the outdoor heat exchanger
• Heat exchanger deicer temperature (Tb)
• Timer (Set to 2 hours at minimum.)
Furthermore, the heat transfer coefficient of the outdoor unit Evaporator is computed from Tc, Te, and
compressor loads.
z
: equipped
–: not equipped
∗
1: RXYQ96/120TA only
7.5 Drain Pan Heater (Option)
When the drain pan heater is connected, it operates below.
Operating conditions
•
Outdoor air temperature < 3°C (37.4 °F)
•
During defrost operation
Part Name
Electric
Symbol
RXYQ72-120TA RXYQ144/168TA Operation
Inverter compressor 1 M1C
z z
RXYQ72TA: 266 Hz
RXYQ96/120TA: 188 Hz
RXYQ144/168TA: 252 Hz + 252 Hz
Inverter compressor 2 M2C —
z
Inverter fan 1 M1F
z z
With high pressure
OFF
←→
Step 4
←→
Step 6
Inverter fan 2 M2F (
z
)
∗
1
z
Electronic expansion
valve (Main)
Y1E
z z
RXYQ72TA: 480 pulses
RXYQ96-168TA: 3,000 pulses
Electronic expansion
valve (Injection)
Y2E
z z
0 pulse
Four way valve Y1S
z z
OFF
Solenoid valve
(Accumulator oil return)
Y2S
z z
ON
Solenoid valve
(Oil return 1)
Y3S
z z
ON
Solenoid valve
(Oil return 2)
Y4S —
z
Ending conditions
• A lapse of 15 min.
• Tb > 11°C (51.8°F) continues for 30 sec. or more
OR
Indoor unit actuator During defrost
Fan
Thermostat ON unit OFF
Stopping unit OFF
Thermostat OFF unit OFF
Electronic expansion valve
Thermostat ON unit Defrost EV opening degree
Stopping unit Defrost EV opening degree
Thermostat OFF unit Defrost EV opening degree
&