Defrosting Operation; Pump-Down Residual Operation - Daikin RMXS-L Series Service Manual

SiUS181305E
3.3

Defrosting Operation

The defrosting operation is performed to solve frost on the outdoor unit heat exchanger when
heating, in order to recover heating capacity.
<Conditions to start>
The defrosting operation is started referring to the following conditions:
 Outdoor heat exchanger heat transfer co-efficiency
 Outdoor heat exchanger temperature (Tb)
 Timer (2 hours at the minimum)
Outdoor heat-exchange co-efficiency is derived from Tc, Te, and the compressor load.
Outdoor unit actuator
Compressor
Outdoor fan
Four way valve (Y1S)
Main electronic expansion valve (Y1E) SH control
Subcooling electronic expansion valve
(Y3E)
Hot gas bypass solenoid valve (Y2S)
Ending conditions
From the preparation to the defrost operation, and from the defrost operation to the post defrost
operation, the compressor stops for 1 minute to reduce noise on changing of the four-way valve.
Indoor fan
Electronic expansion valve of
BP unit
3.4

Pump-down Residual Operation

Outline
When activating the compressor, if there is liquid refrigerant remaining in the heat exchanger, the
liquid refrigerant enters into the compressor and dilutes the oil inside resulting in a decrease of
lubricity. Therefore, the pump-down residual operation is performed to collect the refrigerant in the
heat exchanger when the compressor is down.
Function
Defrost preparation
operation
Upper limit control
STEP 8
ON
0 pulse
OFF
2 min.
Indoor unit actuator
Thermostat ON unit
Stopping unit
Thermostat OFF unit
Thermostat ON unit
Stopping unit
Thermostat OFF unit
Defrost operation
140 Hz Full load
OFF
OFF
480 pulse
0 pulse
ON
 15 min.
 Tb > 11°C
or
(51.8°F)
&
 Ts1 – Te < 5°C
(9°F)
Special Control
Post defrost operation
36 Hz Unload
+2 steps / 20 sec.
(until Pc - Pe > 0.4 MPa)
(134 ftAq)
STEP 8
ON
55 pulse
0 pulse
ON
 160 sec.
 Pc – Pe > 0.4 MPa
or
(134 ftAq)
Operation
OFF
OFF
OFF
SH control
80 pulse
SH control
48