Midea MDV-D22Q1/N1-D Technical Manual page 36

3.3.5. Procedure
Communication wires P Q E have
short circuited or disconnected
Communication wires P Q E are not
connected in a daisy chain
Interference from high voltage (220V
or higher) wires
Communication wires are close to a
source of electromagnetic radiation
such as transformer or strong
fluorescent lamp
The length of communication wire is
Replace indoor 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.
2. The P Q E communication wires should be connected one unit after another in a daisy chain from the master outdoor unit to the final indoor unit. After
the final indoor unit, the communication wiring should NOT be continued back to the outdoor units – that is, do not attempt to form a closed loop.
3. The refrigerant piping, power wiring and communication wiring are typically run in parallel. However the communication wiring should not be bound
together with the refrigerant piping or power wiring. To prevent signal interference, the power wiring and communication wiring should not be run in
the same conduit. If the power supply is less than 10A, a separation of at least 300mm between power wiring and communication wiring conduits
should be maintained; if the power supply is in the range 10A to 50A then a separation of at least 500mm should be maintained.
E1
1
No
2
No
3
No
No
over 1200m
No
Yes
Reconnect the communication wires
Connect the communication wires in a
Yes
daisy chain
Ensure the communication wires and
Yes
high voltage wires are separated
Remove the source of interference, or
Yes
add additional shielding to the
communication wires
Reduce the wire length to less than
Yes
1200m or strengthen the signal
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