Defrosting Operation - Daikin VRV III RXYQ5-54PY1 Service Manual

Si34-601A
3.4

Defrosting Operation

To defrost the outdoor unit heat exchanger while in Evaporator, the defrost operation is conducted to recover the
heating capacity.
[Start conditions]
Referring to the set conditions for the following items, start the defrosting operation.
• Heat transfer coefficient of the outdoor unit heat exchanger
• Heat exchange temperature (Tb)
• Timer (Set to two hours at minimum.)
Furthermore, the heat transfer coefficient of the outdoor unit Evaporator is computed from Tc, Te, and compressor
loads.
Outdoor unit actuator
Compressor
Outdoor unit fan
Four way valve
Main motorized valve (EV1)
Subcooling motorized valve (EV2)
Hot gas bypass valve (SVP)
Accumulator oil return valve (SVO)
Injection (SVT) (RXYQ5P model only)
Ending conditions
* In the case of multi-outdoor-unit system,
Master unit: Performs the operations listed in the table above.
Slave units: Operating units perform the operations listed in the table above.
Non-operating units perform the operations listed in the table above from the Defrost operation.
(Non-operating unit stops during "Defrost preparation operation".)
* Actuators are based on RXYQ14~18P.
Fan
Electronic expansion valve
Function
Defrost preparation
operation
Upper limit control
STEP7
or
STEP8
ON
SH control → 480 pls
0 pls
OFF
ON
OFF
170 sec.
Indoor unit actuator
Thermostat ON unit
Stopping unit
Thermostat OFF unit
Thermostat ON unit
Stopping unit
Thermostat OFF unit
Defrost operation
176 Hz + ON + ON
OFF
OFF
480 pls
0 pls
OFF
ON
OFF
• 10 min.
or
• Tb>11°C
During defrost
Defrost EV opening degree
Defrost EV opening degree
Special Control
Post Defrost operation
124 Hz + OFF + OFF
2-steps increase/20sec.
till Pc - Pe>0.4 MPa
STEP8
ON
55 pls
0 pls
OFF
ON
OFF
• 10 sec.
or
• Pc - Pe>0.4MPa
OFF
OFF
OFF
256 pls
113