Daikin EHYHBH05AAV3, Service Manual

Page: 161 / 170

ESIE13-02A Additional Checks for Troubleshooting
161 Part 4 – Troubleshooting
4
3
4
5
4
6.11 Check No.13 - Check for Inadequate Refrigerant
As criteria for judging whether refrigerant is inadequate or not, refer to the following operating
conditions.
<Diagnosis of inadequate refrigerant>
In cooling operation
1
As suction superheat degree increases due to gas shortage, the electronic expansion valve tends
to open (opens fully) in order to avoid overheat operation.
2
In response to decreased evaporator capacity caused by gas shortage, capacity is controlled in
the inverter in order to maintain low pressure, which results in a decrease in frequency.
3
Because of (1) and (2) above, the compressor frequency decreases despite a large difference
(large load) between temperature set by the remote controller and indoor suction temperature,
resulting that cooling capacity becomes unavailable.
4
If gas shortage worsens, the electronic expansion valve remains fully open and suction superheat
degree further increases. In addition, because the compressor frequency drops to the level of the
lowest frequency (52 Hz) and the refrigerant flow rate decrease, low pressure cannot be
maintained.
<Diagnosis of inadequate refrigerant>
In heating operation
1
As suction superheat degree increases due to gas shortage, the electronic expansion valve tends
to open (opens fully) to avoid overheat operation.
2
As suction superheat degree increases due to gas shortage, compressor frequency decreases
because suction superheat degree is controlled in order to prevent oil to the outdoor 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 indoor suction
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 gas shortage worsens, high pressure becomes smaller than saturated pressure equivalent to
indoor heat exchanger temperature (or indoor suction temperature).