Daikin EWAQ021BAW - Defrosting Operation

ESIE11-05 Special Control
Functional Description 49
3.2 Defrosting Operation
To defrost the outdoor unit heat exchanger while working as Evaporator, the defrost operation is
conducted to recover the heating capacity and runs a reverse cycle.
[Start conditions]
Heat exchange temperature Tb < Tdef (calculated by logic depending on Tamb) and the unit
has been at least 25 min in heating
or Te < 0°C the unit will be forced to take a defrost every 2 hours.
Furthermore, the heat transfer coefficient of the outdoor unit Evaporator is computed from Tc,
Te and compressor loads.
*1 Before switching over to defrost mode the unit closes the EXV for switch over.
*2 Before switching over to normal heating operations the unit closes the EXV for switch over.
* Actuators are based on EWYQ032BA.
Outdoor unit actuator
Defrost preparation
operation
Defrost operation Post Defrost operation
Compressor Upper limit control Unit controlled
124 Hz + OFF + OFF
2-steps increase/20sec.
till Pc - Pe>0.4 MPa
Outdoor unit fan
STEP7
or
STEP8
OFF STEP8
Four way valve ON OFF ON
Main electronic expansion valve
(EV1)
SH control 2000 pls 2000 pls 55 pls
Subcooling electronic expansion
valve (EV2)
0 pls 0 pls 0 pls
Hot gas bypass valve (SVP) OFF OFF OFF
Accumulator oil return valve (SVO) ON ON ON
Ending conditions 170 sec.
 12 min.
 Tb>11C
 10 sec.
 Pc - Pe>0.4MPa
Hydrobox expansion valve K11E *1 PI control *2
Hydrobox expansion valve K21E *1 PI control *2
or
or