Viessmann VITOTRONIC300 Installation And Service Instructions Manual page 74

Troubleshooting
Fault Display
(continued)
Displayed System characteristics
fault code
b0 Control mode.
b1 Control mode.
b5 Control mode.
b6 Control mode.
b7 Boiler is regulated
by the temperature
controller.
b8 Control mode.
bA Mixing valve "Closed". Communication error, PCB
bC Control mode without
remote control.
bd Control mode without
remote control.
bE Control mode without
remote control.
74
Cause
Short circuit, flue gas temperature
sensor
Communication error,
programming unit
Internal fault
Invalid hardware recognized
Boiler coding card faulty
Lead break, flue gas temperature
sensor
extension for heating circuits 2
and 3 with mixing valve
Communication error, remote
control Vitotrol heating circuit
without mixing valve A1 (heating
circuit 1)
Communication error, Vitotrol
remote control, heating circuit
with mixing valve M2 (heating
circuit 2)
Communication fault, remote
control Vitotrol with mixing valve
M3 (heating circuit 3)
Vitotronic 300, GW2B Installation and Service
Measures
Check the flue gas temperature sensor
(see page 125).
Check connections and replace the
programming unit if required.
Check PCB (see parts list)
is plugged in correctly.
Check coding address "92" in the "General"
group; "92:166" must be set.
Note: Code "8A:176" in the "General"
group must be selected for coding
address "92" to be displayed.
Plug in or replace boiler coding card
(see page 37).
Check the flue gas temperature sensor
(see page 125).
Without flue gas temperature sensor:
Set code "1F:0" in the "Boiler" group.
Check that the PCB and ribbon cable are
plugged in, and replace PCB if required.
Check connections, lead (see separate
installation and service instructions)
and coding address "A0" in the "Heating
circuit..." group.
Check connections, lead (see separate
installation and service instructions)
and coding address "A0" in the "Heating
circuit..." group.
Check connections, lead (see separate
installation and service instructions)
and coding address "A0" in the "Heating
circuit..." group.