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© 2022 Staheli West
157
Faults
Fault 225: Burner Modbus Signal Failure
The modbus connection is the way that the
Honeywell Burner Controller communicates with the PLC. If the
connection is lost, the burner will not function properly.
Causes
Troubleshooting
Fixes
• Modbus cable faulty/
unplugged.
• Inspect modbus cable on PLC
port 2 (Panel 2) and top of burner
controller (Panel 1).
• Plug-in/Replace modbus cable.
• Tighten wire terminals on cable
connecting to modbus card.
• Modbus address not set to 78.
• Visually inspect modBus
module.
• See Test 23
• Reset module by turning both
pots to 99, then turn the pots to
78.
• Faulty modbus module.
• 2017 and newer machines:
Unplug burner controller modbus
plug and generator modbus
plug one at a time to determine
whether it is fault 225 or fault
233.
• Replace modbus module.
• PLC modbus connection
shorting.
• Disassemble DB-15 (PLC port 2)
connector and check for shorted/
grounded pins.
Repair/Replace modbus wire
harness.
Fault 226: Burner Controller Did Not Detect That the Louver Actuator Closed
Indicates that the PLC detected louver closure but the burner controller did not (See Fault 20).
Causes
Troubleshooting
Fixes
• Faulty ABD-2 relay in Panel 2.
• Swap with spare 24 V relay in Panel 1.
• Faulty 24 V regulator.
• Regulator giving less than 24
V (Check for 24 V on fuse 4-9 of
panel 3) (Fuses 6-11 on 2015-
2016 machines).May need to
check voltage during “Start All”.
• Replace 24 V regulator.
• Wiring issue.
• Trace the 120 V wires using the
louver actuator wiring diagram.
When the louver is closed T18
should have 120 V. When the
lover is open T19 should have
120 V.
• Use manual mode to open and
close louver for troubleshooting.
• Repair/Replace faulty wiring.