High Pressure Protection; Defrostings - Mitsubishi Electric MSH-07NV Service Manual

2. High pressure protection

During heating operation, the outdoor fan motor is controlled by the indoor coil thermistor RT12 temperature for excess rise
protection of compressor discharge pressure.
Outdoor fan OFF : 52°C (MSH-07/09/12/24), 50°C (MSH-18)
Outdoor fan ON : 48°C (MSH-07/09/12/24), 46°C (MSH-18)
High pressure protection time chart
Indoor coil thermistor
RT12 temperature
52˚C(MSH-07/09/12/24)
50˚C(MSH-18)
48˚C(MSH-07/09/12/24)
46˚C(MSH-18)
Outdoor fan motor
NOTE 1 :When the outdoor fan is OFF in heating, defrosting of outdoor heat exchanger is not detected by the defrost thermis-
tor RT61.
NOTE 2 :When connected to MXZ-32NV-
MSH-18NV- indoor unit sends the data for the temperature to the outdoor unit according to the indoor coil temper-
E3
ature.For the further information,refer to the service manual No.OB185.

3. Defrostings

Defrostings of outdoor heat exchanger is controlled by DEICER P.C. board, with detection by the defrost thermistor RT61.
(1) Defrost starting conditions
When all conditions of a) ~ c) are satisfied, the defrosting operation starts.
a) Under the heat operation, the compressor cumulative operation time exceeds 40 minutes without the defrosting opera-
tion working.
b) The defrost thermistor RT61 reads - 3°C or less.
c) After releasing the high pressure protection 4 minutes and 15 seconds have elapsed.
(2) Defrost terminating conditions
When the condition d) or e) is satisfied, the defrosting operation stops.
d) The defrost thermistor RT61 reads 3.1°C or more.
e) The defrosting time exceeds 10 minutes.
ON
OFF
outdoor unit,the MSH-07/09/12NV-
E1
ON
OFF
,
MSH-07/09/12/18NV-
E1
Outdoor fan motor
turn OFF
Outdoor fan motor
turn ON
and
E2
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