Viessmann B1HF Installation And Service Instructions Manual page 70

Troubleshooting
Fault messages
(cont.)
Displayed fault System characteristics
code
71 Burner in a fault state
73 Burner in a fault state
74 Burner locked out.
Internal circulation pump off.
No central heating and no
DHW heating.
77 Burner in a fault state
89 No central heating and no
DHW heating
91 Function of affected exten-
sion in emergency mode
92 Function of the relevant elec-
tronics module in emergency
mode
95 Burner off
100 Electronics modules connec-
ted to PlusBus not function-
ing
70
Cause
Fan speed too low
Internal communication
error
System pressure too low
HBMU heat management
unit data memory
Internal circulation pump
blocked
DIO electronics module
communication error
ADIO electronics module
communication error
OpenTherm remote con-
trol unit not connected
Voltage error PlusBus
Measures
Check fan for blockage.
■
Check setting for gas type and
■
flue system.
Reset the appliance.
Reset the appliance.
If the fault occurs repeatedly, re-
place the HBMU heat management
unit. See chapter "Replacing the
HBMU heat management unit".
Top up with water.
Vent the system.
If the fault occurs repeatedly:
Check system pressure sensor
■
with external pressure gauge.
Check diaphragm expansion
■
vessel pre-charge pressure.
Check settings for set system
■
pressure and range.
Reset the appliance.
If the fault occurs repeatedly, re-
place the HBMU heat management
unit. See chapter "Replacing the
HBMU heat management unit".
Check circulation pump. Replace if
necessary.
Check connections to DIO elec-
tronics module and connection to
HBMU heat management unit.
Check setting in the commission-
■
ing assistant and correct if re-
quired.
Check connections and leads to
■
the ADIO electronics module.
Check PlusBus voltage level
■
(24 to 28 V).
Check subscriber number on ro-
■
tary switch S1 and correct if re-
quired.
Check connection to the Open-
■
Therm remote control. unit.
If OpenTherm is not required, set
■
C.7 in the commissioning assis-
tant to a value other than 14.
Check whether the PlusBus power
supply on the HBMU heat manage-
ment unit is OK: Remove all con-
nected PlusBus components and
reconnect one by one.
Check that no more than 1 Vitotrol
200-E is connected to the HBMU.
Check whether there is a short cir-
cuit at the PlusBus cable.