Midea V8 VRF Series Service Manual page 74

6.1.26 C77, C78 - Abnormal communication between IDU main control board and 1# function expansion
board, abnormal communication between IDU main control board and 2# function expansion board
Error display
Faulty IDU: The fan continues running, and the EXV is closed. Other IDUs of the same system:
Error impact operate normally.
ODU of the same system: operate normally.
If the main control board of an IDU has lost communication with 1# function expansion board or 2#
Error trigger
function expansion board for 2 min
Error recovery
Automatic recovery
Possible cause See the Troubleshooting section.
Troubleshooting
Note: The main control board of the IDU cannot be directly connected to the function expansion
board. Instead, an adapter board has to be used. See Figure 1 below:
Figure 1 Wiring diagram of function expansion board, adapter board, and IDU main control board
Function expansion
board
Digital display
C77/C78
Adapter board
Two-core
communication cable
(configured on site)
Panel, display box, and wired controller
Cause 1: The co mmuni cation
cable between th e function
expansion bo ard and th e
ada pte r bo ard becomes
disconnected or sho rt ci rcu ited
Cause 2: The co mmuni cation
cable between th e function
expansion bo ard and th e a dapter
boa rd h as become loose or is
connected to a wrong port
Cause 3: The IDU main control
boa rd i s damage d
Cause 4: The fun ction expansion
boa rd i s damage d
Ten-core
communication
cable
(configured by
factory)
V8 VRF Indoor Units
Display position
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 IDU
Replace th e function
expansion bo ard
IDU main control
board
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