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On-Defrost Operation Control; Refrigerant Recovery Control - Mitsubishi Electric PURY-HP72 Service Handbook

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[5-2 Outdoor Unit Control ]
5-2-8

ON-defrost operation control

(1) ON-defrost operation start conditions
On-defrost operation will start when all the conditions listed in the table below are met (outside temperature, cumulative com-
pressor operation time, and piping temperature).
SW4 (848) must be set to ON to perform ON-defrost operation.
Outside temperature (TH7)
Cumulative compressor operation time
Piping temperature (TH6)
(2) Valve operation during ON-defrost cycle
Outdoor unit fan
SV1a
SV5b
SV9
SV10
SV11
SV4a
SV4b
SV4d
21S4a
(3) ON-defrost operation end conditions
ON-defrost operation will end when the ON-defrost operation time in the table below is reached or when the piping tempera-
tures (TH9 and TH11) have remained above the temperature in the table below for three minutes.
ON-defrost operation time
Piping temperature (TH9, TH11)
5-2-9

Refrigerant Recovery Control

Refrigerant recovery is performed for each BC port during heating operation to prevent the refrigerant from accumulating in-
side the units that are stopped (in the fan mode), in the cooling mode, or in the heating Thermo-OFF mode.
It is also performed during cooling operation to prevent an excessive amount of refrigerant from accumulating in the outdoor
heat exchanger.
Starting criteria for the refrigerant recovery cycle (during Cooling-only, Cooling-main, Heating-only, or Heating-main
mode)
The refrigerant recovery mode starts when all of the following conditions are met:
1) When 5 minutes have passed in the Heating-only or Heating-main mode or 30 seconds have passed in the Cooling-only or
Cooling-main mode since the completion of the previous refrigerant recovery cycle AND the when following conditions are
met.
TH4 > 105°C [221°F]
2) When the port is not in the 4-minute restart delay mode
Starting criteria for the refrigerant recovery cycle (during Cooling-only, Cooling-main, Heating-only, or Heating-main
mode)
1) When the port is in the cooling Thermo-OFF, fan, or stop mode
SVC at the port turns on for 30 seconds.
2) The opening of LEV1 and LEV3 is increased.
HWE13080
Single unit
When 30 minutes have passed
TH6>TH7−8°C [14°F]
Single unit
Top HEX in defrost
Bottom HEX in de-
cycle
frost cycle
In operation
In operation
ON
OFF
OFF
ON
OFF
OFF
OFF
ON
OFF
OFF
OFF
Single unit
When 20 minutes have passed When 30 minutes have passed
- 129 -
Combination units
3.5°C [38.3°F] - 7.0°C[44.6°F]
When 50 minutes have passed
TH6>TH7−10°C [18°F]
Combination units
Unit in defrost cycle
Stopped
OFF
OFF
OFF
ON
ON
ON
ON
OFF
OFF
OFF
ON
Combination units
6°C [43°F]
Unit in operation
In operation
ON
OFF
OFF
OFF
ON
ON
OFF
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