Defrost Control - Daikin SkyAir RZR-TA Series Service Manual

SiUS281811E
3.3

Defrost Control

Pc: High pressure sensor detection value
Pe: Low pressure sensor detection value
Tb: Heat exchanger deicer temperature
Tc: High pressure equivalent saturation temperature
Te: Low pressure equivalent saturation temperature
Ts1: Suction pipe temperature detected by thermistor R3T
Defrost control is performed to melt frost on the outdoor heat exchanger when heating, and thus
recover heating capacity.
Starting conditions
Defrost operation is started referring to the following conditions.
 Outdoor heat exchanger heat transfer coefficiency
 Timer setting (Two hours at the minimum)
In addition, outdoor heat exchanger coefficiency is derived from Tc, Te, and compressor load.
Electric Symbol
Outdoor unit
18/24
actuator
class
Compressor M1C
Outdoor fan M1F
Main electronic Y1E
expansion valve
Subcooling —
electronic
expansion valve
Four way valve Y1S
Hot gas bypass Y2S
valve
Ending conditions
 Between (A) defrost preparation control and (B) defrost control, and between (B) defrost control
and (C) control after defrost, the compressor stops for 1 minute to reduce noise on changing of the
four way valve.
Fan
Electronic expansion valve
Part 4 Functions and Control
(A) Defrost preparation
30/36/42/48
control
class
M1C Upper limit control
M1F STEP 8
M2F
Y1E SH control
Y3E 0 pulse
Y1S ON
— OFF
2 minutes
Indoor unit actuator
Thermostat ON unit
Non-operating unit
Thermostat OFF unit
Thermostat ON unit
Non-operating unit
Thermostat OFF unit
(B) Defrost control
140 Hz Full load
OFF
480 pulse (Fully open)
0 pulse
OFF
ON
x 12 minutes
OR
x Tb > 11°C (51.8°F)
&
x Ts1 – Te < 5°C (9°F)

Defrost control

416 pulse
256 pulse
416 pulse
Special Control
(C) Control after defrost
Increases 2 steps every 20
seconds from minimum
frequency until Pc – Pe >
0.4 MPa (58 psi) is
achieved.
STEP 8
55 pulse
0 pulse
ON
ON
x 160 seconds
OR
x Pc – Pe > 0.4 MPa
(58 psi)
OFF
OFF
OFF
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