Daikin ERQ, Service Manual

Page: 39 / 260

ESIE09-05 Special Control
Function 29
3.3 Defrosting Operation
The defrost operation is performed to solve frost on the outdoor unit heat exchanger when
heating, and the heating capacity is recovered.
[Conditions to start]
The defrost operation is started referring following conditions.
„
Outdoor heat exchanger heat transfer co-efficiency
„ Temperature of heat-exchange (Tb)
„ Timer (2 hours at the minimum)
In addition, outdoor heat-exchange co-efficiency is derived from Tc, Te, and the compressor
load.
* From the preparing operation to the defrost operation, and from the defrost operation to the
operation after defrost, the compressor stops for 1 minute to reduce noise on changing of the
four way valve.
Outdoor unit actuator
Defrost preparation
operation
Defrost operation Post Defrost operation
Compressor Upper limit control 140 Hz Full load
2-step increase from
36 Hz Unload to
(Pc - Pe>0.4 MPa)
every 20 sec.
Outdoor unit fan STEP8 OFF STEP8
Four way valve ON OFF ON
Main electronic expansion valve
(EV1)
SH control 480 pls 55 pls
Subcooling electronic expansion
valve (EV3)
0 pls 0 pls 0 pls
Hot gas bypass valve (SVP) OFF ON ON
Ending conditions 2 min.
•
15 min.
• Tb>11°C
•
Ts1 - Te<5°C
• 160 sec.
•
Pc - Pe>0.4MPa
or
&
{
or
AHU actuator Heating oil return operation
Fan
Thermostat ON unit Field setting
Stopping unit OFF
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