SiME332106E
Special Control
Part 4 Functions and Control
67
7.3 Defrost Control
To defrost the outdoor heat exchanger while in evaporator, the defrost control is conducted to
recover the heating capacity.
Tc : High pressure equivalent saturation temperature
Te : Low pressure equivalent saturation temperature
Defrost control is not conducted before 40 minutes have elapsed from the start of heating
operation.
After 40 minutes have elapsed, defrost control starts when the following items meet the
reference values.
Heat transfer coefficient of the outdoor heat exchanger
(The heat transfer coefficient of the outdoor heat exchanger is computed from Tc, Te,
and compressor loads.)
Outdoor heat exchanger deicer temperature (Tb)
Defrost control starts every 2 hours, even if the reference values are not met.
Starting conditions
Part Name
Electric
Symbol
RXYMQ-A
Function
Compressor motor
M1C
RXYMQ4AVMK: 70 rps
RXYMQ4-6AYFK: 79 rps
Fan motor
M1F
With high pressure
OFF ←→ Step 4 ←→ Step 6
Electronic expansion valve
(Main)
Y1E
480 pulses
Electronic expansion valve
(Injection)
Y2E
0 pulse
Electronic expansion valve
(Refrigerant jacket)
Y3E
0 pulse: closed
0-480 pulse: open (when fin temperature increases)
Electronic expansion valve
(Refrigerant auto charge)
Y4E
Minimum pulse
Four way valve
Y1S
OFF
Ending conditions
A lapse of 15 minutes
Tb>11°C continues for 30 seconds 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
