Si30-408
Points of Analysis
Service Checker Type3 Application Edition
185
(Case Example) VRV II Heat recovery type: Malfunction of heating
Unit supplied: REYQ16M (Heat recovery type)
Malfunction conditions:
Indoor units produce abnormal sounds sometimes and do not heat up.
Referring to Checker data on occurrence of malfunction while in all-unit heating
operation (graph shown on the following page)
The suction pipe temperature has risen up to approximately 70°C.
Low pressure has reached approximately 1.5 MPa.
Discharge pipe stepping down control has been activated.
High pressure has not been stabilized.
*
According to the data above, it can be judged that high pressure gas may be bypassed to
low pressure side somewhere. Furthermore, since a temperature at the stop valve area of
suction gas pipe provided on site was measured and found to be approximately 50°C, it can
be judged that the gas is bypassed on the indoor unit side.(The suction gas pipe is only used
in cooling operation. Furthermore, this pipe is directly connected to the compressor, thus
causing no flow of high pressure gas.)
Referring to verification data on indoor units
Procedure for indoor unit operation
Among five indoor units connected, stop four indoor units in cooling mode (in order to set
the opening degree of the indoor unit expansion valve to 0 pls).
Operate the remaining one indoor unit in heating test operation mode. (The reason is that if
there is no indoor unit with thermostat ON while in heating mode, no high pressure gas will
flow in the discharge gas pipe.)Making measurement of indoor unit operation data according
to the aforementioned procedure will have an indoor unit which has an increased gas pipe
temperature even though no refrigerant flow at 0-pls opening degree of the electronic
expansion valve and the liquid and suction pipes are only connected. As a result, it can be
judged that the indoor unit with the increased gas pipe temperature has discharge and
suction pipes connected other way round.
Cause of malfunction
On the outdoor unit side, discharge gas was bypassed to the suction pipe. As a result, the
suction pipe temperature rose following with a rise of discharge pipe temperature and the
activation of discharge pipe temperature control, which disabled the continuous operation of
the compressor leading to the unstable state of high pressure. Furthermore, on the indoor
unit side, due to no discharge gas flow, no indoor units heated up and back pressure was
applied to the check valve, thus resulting in the occurrence of abnormal sounds.
Countermeasure
Pipes of indoor units (1), (3), and (4) provided on site were rectified.
