Trane 4TVH0086FE000AA Service Manual page 77

Procedure
Communication wires P Q E have short
circuited or disconnected
Communication wires P Q E are not
connected in a daisy chain
IDU power supply is abnormal
Wires between outdoor main PCB and
electric control box communication
terminals block are loose
Interference from high voltage (220V or
Communication wires are close to a
source of electromagnetic radiation such
as transformer or strong fluorescent lamp
The length of communication wire is over
Replacing outdoor main PCB resolves the
Replace electric control box
communication terminals block
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.
E2
1
No
No
No
No
higher) wires
No
No
1200m
No
error
No
Yes
Reconnect the communication wires
Connect the communication wires in a
Yes
Yes
Ensure normal power supply
Yes
Ensure the wires are connected properly
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
76
daisy chain