M thermal Mono
58 200204
Midea M thermal Mono Service Manual
Procedure
Communication wires P Q E have short
circuited, disconnected or are
misconnected
1
Reconnect the communication wires
Communication wires P Q E are not
connected in a daisy chain
Connect the communication wires in a
daisy chain
Wires between outdoor main control
board for refrigerant system and electric
control box communication terminals
block are loose
Ensure the wires are connected properly
Interference from high voltage (220V or
higher) wires
Ensure the communication wires and
high voltage wires are separated
Communication wires are close to a
source of electromagnetic radiation such
as transformer or strong fluorescent lamp
Remove the source of interference, or
add additional shielding to the
communication wires
Replacing electric control box
communication terminals block resolves
the error
Replace hydronic system main PCB
Notes:
1. Measure the resistance among P, Q and E. The normal resistance between P and Q is 120Ω, between P and E is infinite, between Q and E is infinite.
Communication wiring has polarity. Ensure that the P wire is connected to P terminals and the Q wire is connected to Q terminals.