Sinclair SDV 6 Service Manual page 92

8.1.23 C74 - Abnormal communication between the linked FAPU and master IDU (series setting)
Note:
1) The type of FAPU may be HRV, VRF fresh air IDU and so on.
2) Series setting: The air supply side of the linked FAPU is directly connected to the air return side of the master IDU through an
air duct. A wired controller is used to set this installation method as a series connection.
Error display
Error impact
Error trigger
Error recovery
Possible cause
Troubleshooting
Digital display
The master IDU and the linked FAPU: stop. Other IDUs of the same system: operate normally.
ODU of the same system: operate normally.
If the main control board of the master IDU has lost communication with the main control board of
the FAPU for 2 min
Automatic recovery
 The main control board of the FAPU is damaged.
 The master IDU's main control board is damaged.
 Communication cables are loose or the communication port is faulty.
 Communication cables have short-circuited or been cut off.
C74/C75
Note:
1. The error code can be queried after the FAPU is connected to the wired controller or the display
box.
Cause 1: The communication cable
between the main control board of the
FAPU and the main control board of the
master IDU is disconnected or short
circuited
Cause 2: The communication cable
between the main control board of the
FAPU and the main control board of the
master IDU has become loose or is
connected to a wrong port
Cause 3: The main control board of the
master IDU is damaged
Cause 4: The main control board of the
FAPU is damaged
Display position (master IDU)
Panel, display box, and wired controller
Replace the
communication cable
and properly connect
the cable
Properly connect the
cables and ensure
they are connected to
the right ports
Replace the main
control board of
master IDU
Replace the main
control board of the
FAPU
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