Sinclair SDV 6 Service Manual page 93

8.1.24 C75 - Communication fault between linked FAPU and master IDU (non-series setting)
Note:
1) The type of FAPU may be HRV, VRF fresh air IDU and so on.
2) Series setting: The linked FAPU and the master IDU are connected to the air supply duct and air return duct respectively a nd
separately. A wired controller is used to set this installation method as a non-series connection.
Error display
Error impact
Error trigger
Error recovery
Possible cause
Troubleshooting
90
Digital display
Master IDU: operates normally. FAPU: stops. 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.
Display position (master IDU)
Panel or display box
Spot check interface
query
Cause 1: The co mmuni cation
cable between th e main control
boa rd o f th e FAP U and the ma in
control board of the master IDU
is d isconn ected or sh ort circuited
Cause 2: The co mmuni cation
cable between th e main control
boa rd o f th e FAP U and the ma in
control board of the master IDU
has become l oose o r is
connected to a wrong port
Cause 3: The ma in con trol boa rd
of the master IDU is damag ed
Cause 4: The ma in con trol boa rd
of the FAPU i s damaged
Wired controller
Error code is not
displayed
Replace th e
commu nicatio n cable an d
prop erly conn ect the
cable
Pro perly conn ect the
cables and ensure th ey
are conne cted to the right
ports
Replace th e main control
boa rd o f th e master IDU
Replace th e main control
boa rd o f th e FAP U