91
Fault code dis-
played
System characteristics
Cause
Measures
4D
Mixer being closed
Incorrect assignment of
extension for mixer, heat-
ing circuit 3
Check and adjust rotary selector
S1 (see page 109)
50
No DHW heating
Short circuit, cylinder tem-
perature sensor
Check sensors (see page 104)
51
No DHW heating
Short circuit, outlet tem-
perature sensor
Check sensor (see page 104)
58
No DHW heating
Lead break, cylinder tem-
perature sensor
Check sensors (see page 104)
59
No DHW heating
Lead break, outlet temper-
ature sensor
Check sensor (see page 104)
70
Burner blocked
Gas pressure switch pre-
vents burner start.
■
Check gas supply (gas pres-
sure).
■
If installed: check gas pressure
switch for correct function.
If necessary, disconnect plug 111
from the control unit and check
whether the burner starts.
71
Burner blocked
Mains voltage too low
Check the power supply.
73
Burner blocked
Feedback input from inter-
nal H1 extension prevents
burner start.
Check that internal H1 extension
and any devices connected to it
are correctly connected and work-
ing properly (internal: plug 53/96
power interruption)
74
Burner blocked or in a fault
state
Temperature limiter earth
fault
Check temperature limiter, con-
necting cables and plug-in connec-
tion for connection (contact) to
earthed components. Remove con-
tact if necessary.
Press reset button
R
.
75
Burner blocked or in a fault
state
Internal H1/H2 extension
earth fault
Check internal H1/H2 extension,
connecting cables and plug-in con-
nection for connection (contact) to
earthed components. Remove con-
tact if necessary.
Press reset button
R
.
76
Burner blocked or in a fault
state
Gas pressure switch earth
connection
Check gas pressure switch, con-
necting cables and plug-in connec-
tion for connection (contact) to
earthed components. Remove con-
tact if necessary.
Press reset button
R
.
80
Burner in a fault state
Insufficient gas supply
Test static gas pressure and gas
flow pressure.
Check that on-site gas line and gas
flow switch are correctly sized.
Note
If the building pressure regulator
has a leak, you may notice rising
pressure when the burner is idle.
The gas flow switch may respond if
the system is restarted.
Troubleshooting
Fault codes
(cont.)
5789 302 GB
Diagnosis
Summary of Contents for B2TB
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Page 117: ...117 Parts lists Hydraulics 5789 302 GB Components ...
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