MITSUBISHI ELECTRIC MXZ-24UV - Manual (Page 26)

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Frequency drop by current
protection When the outdoor unit input current exceeds 22.5 A, the compressor
operates at reduced frequency.
These symptoms do not mean any
abnormality of the product, but check the
following points.
• Air filter clogging.
• Amount of gas.
• Short cycle of indoor/outdoor air flow.
Display Detecting method Detecting method Check points
Symptom Outdoor unit operates. (The compressor operates at reduced frequency.)
Frequency drop by overload
protection When the compressor load exceeds the specified value, the compres-
sor operates at reduced frequency.
Frequency drop by high pres-
sure protection When indoor pipe temperature exceeds 55˚C during heating, the com-
pressor operates at reduced frequency.
Frequency drop by defrosting
in cooling When the indoor pipe temperature falls to 6˚C or below during cooling,
the compressor operates at reduced frequency.
Frequency drop by discharge
temperature protection When the discharge temperature exceeds 110˚C, the compressor oper-
ates at reduced frequency.
Frequency drop by high pres-
sure switch protection
When the high pressure exceeds 2.75MPa (28 kgf/cm 2 -G), the com-
pressor operates at reduced frequency. In addition, the fan speed
changes.
• Amount of gas.
• Outdoor unit air passage.
Low discharge temperature
protection
When the state with low discharge temperature of which 50˚C in COOL
and 48.4 or less in HEAT for 20 minutes, the compressor operates con-
tinuously.
Check the amount of gas.
• Replace the outdoor controller board.
• Check the contact of LEV board connec-
tors.
Defrost thermistor abnormality
When a short or open circuit occurs in the defrost thermistor during
heating
* In this case, the compressor continues to operate.
• Defrost thermistor characteristic.
• Contact of P. C. board connectors.
Display Detecting method Detecting method Check points
Symptom Outdoor unit operates.
Power factor detection abnor-
mality When the compressor power factor cannot be detected
* In this case, the compressor keeps running.
• Compressor wiring.
d d8 8
(d8)
d d9 9
(d9)
d d77
(d7)
d d6 6
(d6)
d d3 3
(d3)
d d11
(d1)
e e77
(E7)
h h44
(h4)
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