Si20-701_B Troubleshooting by Remote Controller
480
<Diagnosis of inadequate refrigerant>
In heating operation
(1) As suction superheated degree increases due to
refrigerant shortage, the electronic expansion valve
tends to open (opens fully) to avoid overheat
operation.
(2) As suction superheated degree increases due to
refrigerant shortage, compressor frequency
decreases because suction superheated degree is
controlled in order to prevent oil to the outdoor unit
heat exchanger from being retained.
(3) Because of (1) and (2) above, evaporator capacity
and compressor frequency decrease despite a large
difference (large load) between temperature set by
the remote controller and suction air temperature,
resulting that high pressure cannot be maintained and
heating capacity becomes unavailable. Also a
decrease in evaporator capacity frequently puts the
system in defrost operation.
(4) If refrigerant shortage worsens, high pressure
becomes smaller than saturated pressure equivalent
to indoor heat exchanger temperature (or suction air
temperature).
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