Defrost Control - Daikin FTKS20D3VMW Service Manual

SiENBE12-713

3.10 Defrost Control

Outline Heat Pump Only
Defrosting is carried out by the cooling cycle (reverse cycle). The defrosting time or outdoor
heat exchanger temperature must be more than its fixed value when finishing.
Detail
Conditions for Starting Defrost
Under the conditions that the system is in heating operation, 6 minutes after the compressor is
started and more than 38 minutes of accumulated time pass since the start of the operation or
ending the defrosting.
When the outdoor air temperature and the outdoor heat exchanger temperature meet the
following condition for 60 seconds, the defrost control starts.
Conditions for Canceling Defrost
The target heat exchanger temperature as the canceling condition is selected in the range of
4°C≤Te≤12°C according to the air temperature as the following formula.
The target heat exchanger temperature = –(45/64)×(ambient temperature)+14
The defrost operation surely operates in 120 seconds after the start. (A→B)
After then the defrost operation stops at the following conditions.
1. When the heat exchanger temperature reaches the target heat exchanger temperature.
2. When 650 seconds have passed after the start even if the heat exchanger temperature does
Function and Control
A< –(19/256)×B+(45/64)×C
A: outdoor heat exchanger temperature
B: output frequency
C: outdoor air temperature
(B→C)
not reaches the target heat exchanger temperature. (C)
38 minutes
60 seconds
6 minutes
1
Preparation 0
signal
1
Defrosting 0
signal
ON
Compressor
OFF
ON
4-way valve
OFF
ON
Fan
OFF
Operating room
Motorized valve
opening
Operation stopped
room Motorized
valve opening
2YC45 : 82Hz
0Hz
120 seconds
650 seconds
Start
0 seconds
5 seconds
350 Pulse
450 Pulse
160 Pulse
Control Specification
PI control
60 seconds
Completion
5 seconds
Initial opening
400 Pulse
Initial opening
0 Pulse
(R6959)
91