Defrosting Operation - Daikin FCQ18PVJU Service Manual

SiUS28-902_a
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 under the following conditions:
 Outdoor heat exchanger heat transfer co-efficiency
 Temperature of heat-exchange (Tb)
 Timer (2 hours at the minimum)
Outdoor unit actuator
Compressor
Outdoor unit fan
Four-way valve
Main electronic expansion valve
(EV1)
Subcooling electronic expansion
valve (EV2)
Hot gas bypass valve (SVP)
Receiver gas discharging valve
(SVG)
Ending conditions
* 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.
Fan
Electronic expansion valve
Function
In addition, outdoor heat-exchange co-efficiency is derived from Tc, Te, and the compressor
load.
Defrost preparation
operation
52 Hz
STEP 8
ON
SH control
0 pls
OFF
ON
130 sec.
Indoor unit actuator
Thermostat ON unit
Stopping unit
Thermostat OFF unit
Thermostat ON unit
Stopping unit
Thermostat OFF unit
Defrost operation
177 Hz
OFF
OFF
1400 pls
0 pls
ON
ON
• 15 min.
or
• Tb >51.8°F
During defrost
Special Control
Post Defrost operation
2-step increase from
52 Hz to
(Pc - Pe>58 psi)
every 20 sec.
STEP 8
ON
200~400 pls
0 pls
ON
OFF
• 160 sec.
or
• Pc - Pe>58 psi
OFF
OFF
OFF
500 pls
500 pls
500 pls
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