J3E Low Bus Voltage Fault - Midea V8 VRF Series Service Manual

V8 VRF Indoor Units
6.1.48 J3E - Low bus voltage fault
Error display
The faulty IDU stops. Other IDUs of the same system: operate normally.
Error impact
ODU of the same system: operate normally.
Error trigger
When the bus voltage (DC voltage) is below the threshold value of the driver (165 V)
Error recovery
Automatic recovery
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Possible cause
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Note:
1. Please refer to the figure below when measuring voltage between P and N. Make sure P/N
measuring points are selected according to PCB type.
Troubleshooting
2. Please observe the following rule when replacing the fan drive board: For units whose fan drive
board is welded onto the main control board, if either the fan drive board or main control board
becomes faulty, the whole control board has to be replaced.
96
Digital display
The input voltage is too low, resulting in low bus voltage.
The input voltage encounters transient drop and interruption, resulting in too low transient
bus voltage.
The fan drive board is damaged, so the bus voltage detection circuit becomes abnormal.
The IDU main control board is damaged.
Cause 1: Measure the input voltage of
the IDU. If the voltage is significantly
lower than the normal value ( 140 V)
Cause 2: If the input power supply is
normal, and the voltage (DC) between
P and N is normal (the normal voltage
J3E
cleared after causes 1/2 have been
eliminated, the main control board of
PCB type 1
P/N measuring point
N
P
Panel or display box
Spot check interface query
or the voltage interrupts or drops
instantaneously, the power supply is
abnormal
is about 310 V), it indicates that the
voltage detection circuit for fan drive
board is abnormal (1)
Cause 3: If the error cannot be
the IDU is damaged
PCB type 2
P/N measuring point
(front of PCB)
Display position
Wired controller
Error code is not displayed
Fix the power supply
Replace the fan drive
board (2)
Replace the main
control board of the
IDU
P/N measuring point
(back of PCB)
P
P
N