Midea SMK-60/CGN8, Service Manual

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M-Thermal Split
22 201909
Midea
M
-Thermal
Spli
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Ser
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Manua
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5.5 Voltage Protection Control
This control protects the M-Thermal Split from abnormally high or abnormally low voltages.
Figure 3-5.6: Compressor voltage protection control
When the phase voltage of AC power supply is at or above 265V for more than 30 seconds, the system displays H7
protection and the unit stops running. When the phase voltage drops below 265V for more than 30 seconds, the
refrigerant system restarts once the compressor re-start delay has elapsed. When the phase voltage is below 172V, the
system displays H7 protection and the unit stops running. When the AC voltage rises to more than 180V, the refrigerant
system restarts once the compressor re-start delay has elapsed.
5.6 DC Fan Motor Protection Control
This control protects the DC fan motors from strong winds and abnormal power supply. DC fan motor protection occurs
when any one of the following the following three sets of conditions are met:

Outdoor ambient temperature is at or above 4°C and actual fan speed differs from target fan speed by 200rpm or
more for more than 3 minutes.

Outdoor ambient temperature is below 4°C and actual fan speed differs from target fan speed by 300rpm or more for
more than 3 minutes.

Actual fan speed is less than 150rpm for more than 20 seconds.
When DC fan motor protection control occurs the system displays the H6 error code and the unit stops running. After 3
minutes, the unit restarts automatically. When H6 protection occurs 10 times in 120 minutes, the HH error is displayed.
When an HH error occurs, a manual system restart is required before the system can resume operation.
5.7 Water Side Heat Exchanger Anti-freeze Protection Control
This control protects the water side heat exchanger from ice formation. The water side heat exchanger electric heater is
controlled according to outdoor ambient temperature, water side heat exchanger water inlet temperature and water side
heat exchanger water outlet temperature.
In cooling mode, if inlet water temperature or leaving water temperature or auxiliary heat source leaving water
temperature is below 4°C, the anti-freeze protection actions. In heating/DHW mode, if ambient temperature is below 3°C
and inlet water temperature or leaving water temperature or auxiliary heat source leaving water temperature is below 5°C,
the anti-freeze protection actions. In heating/DHW mode, leaving water temperature is below 2°C, the anti-freeze
protection actions.
When water side heat exchanger anti-freeze protection occurs the system displays error code Pb and the unit stops
running.
Voltage ≥ 265V for 30s
or Voltage ≤ 172V
Voltage < 256V for 30s
or Voltage ≥ 180V
Normal operation
Compressor voltage protection, error code H7 is displayed
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