8-9
Fault
display
Probable cause and remedyFault name and meaning
BUS Communications error
(Option Unit)
A communications error
occurred at the Option Unit.
• Communications cable wired incorrectly, short-circuited, or
disconnected.
→ Check and correct the communications cable wiring.
• Data destroyed by noise.
→ Change to a dedicated communications cable or to
shielded cable, and mask the shield or ground it at the
power supply.
→ Use a dedicated communications power supply, and
connect a noise filter to the power supply input side.
• Option Unit is damaged.
→ If communications errors frequently occur and there is no
problem with the wiring, replace the Option Unit.
OFF Power supply error
Control power supply voltage
is insufficient.
• No power supply is provided.
→ Check and correct the power supply wire and voltage.
• Terminal screws are loose.
→ Check and tighten the terminal screws.
• Operator connectors are faulty.
→ If only the Operator indicator is not lit, (i.e., if the RUN
and ALARM indicators are lit), check and correct the
Operator’s connectors.
• The Inverter is damaged.
→ Replace the Inverter.
Note This fault is displayed for 200 and 400-V, 5.5-/7.5-kW Inverters only.
Maintenance Operations Chapter 8
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