Toyotomi KURO Mini Service Manual page 57

（19）Function protection prompt of frequency conversion external machine
Cause: In the regular running of the air conditioner, for some nonfaulted
status, it may need the compressor to shut down or limit or lower the
frequency so as to protect the normal operating of the entire cooling system
(eg. defrosting, slight undercooling, over pressure, overcurrent, etc.). These
problems are not considered as errors and would not be reflected in the
Explanation of
internal machine, however as to make sure the maintenance personnel is
error familar with the running status of the air conditioner, three indicator lights are
used on the main external control panel for reference of the maintenance
personnel.
Including: over current protection, cooling overload protection, indoor
heating high temperature protection, indoor cooling freezing protection, over
pressure and under pressure protection.
Tools required
Multimeter.
for inspection
Frequent
Regular protection, system blockage, power supply not as usual, resistance
value of sensor drifts or is used wrong.
problematic part
1. Defrosting: with a defrosting signal, meaning the air conditioner is under
defrosting procedure and it is normal, but if there is frequent defrosting, it
shall be specifically noted if heat exchange of the external unit is faulted, if
the fan revolving speed is low and if the resistance value of the coil sensor is
drifted or the temperature is inaccurately measured or it is damaged.
2. Over current protection: it is more possible to appear under high
temperature cooling status and the over current of compressor is usually
reflected by over high load of the compressor. It is normal if such protection
appears under a very high temperature cooling status but not under low
temperature low load status.
3. Cooling overload protection: it is more possible when the frequency
conversion machine is under a high temperature cooling status. When the
outdoor coil sensor senses the temperature is too high, as to provent the
compressor from overload, it would possitively lower the frequency and it is
normal for the protection under the high temperature cooling status.
4. Indoor high temperature heating protection: it is more possible when the
frequency conversion machine is under a high temperature heating status.
Inspection
When the indoor coil sensor senses the temperature is too high, as to provent
procedure and
the compressor from overload, it would possitively lower the frequency and it
key points
is normal for the protection in a warm room.
5. Indoor cooling freezing protection: it is more possible to appear under a
low temperature cooling status. When the indoor coil sensor senses the
temperature is too low, as to prevent the heat exchanger of the internal
machine from frosting, it would possitively lower the frequency and it is
normal for the protection in a low temperature room.
6. Over or under pressure protection: this protection is a pilot protection for
the "over or under pressure error". When the power pressure is too high or too
low but not so high or so low to reach limit for shutting down (within
165V-265V), it would limit and lower the frequency first to reduce the air
conditioner's needs for the power to keep teh air conditioner running. This
protection is for the adaption to a unstable power environment and when
there is such protection prompt, it usually means it is possible for "OVP and
UVP error" and the maintenance personnel shall especially note.
7. Cooling overload protection, indoor high temperature heating protection
and indoor coolign freezing protection are also possible related to the drift of
the resistance value of the sensor.
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