Defrosting Operation - Daikin VRV II RXYQ8MY1K Service Manual

Si39-502A
3.3

Defrosting Operation

To defrost the outdoor unit heat exchanger while in heating operation, 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 heat exchanger 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)
Receiver gas discharging valve
(SVG)
Non-operating unit liquid pipe stop
valve (SVSL)
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".)
Fan
Electronic expansion valve
Function
Defrost preparation
operation
Upper limit control
STEP7
or
STEP8
ON
SH control
0 pls
OFF
OFF
ONs
130 sec.
Indoor unit actuator
Thermostat ON unit
Stopping unit
Thermostat OFF unit
Thermostat ON unit
Stopping unit
Thermostat OFF unit
Defrost operation
143 Hz + ON + ON
OFF
OFF
2000 pls
0 pls
ON
OFF
ON
• 12 min.
or
• Ts >11°C
During defrost
Special Control
Post Defrost operation
1-step increase from
(74 Hz + OFF + OFF) to
(Pc - Pe>0.4 MPa)
STEP8
ON
200 pls
0 pls
ON
OFF
ON
• 160 sec.
or
• Pc - Pe>0.4MPa
OFF
OFF
OFF
512 pls
512 pls
512 pls
63