Bosch Control 8311 Operating Instructions Manual page 28

Operating and fault displays
Display text/Observation/
Fault
DHW remains cold
Thermal disinfection failed
Manual operation activated
Flue gas test is active
Position test for temp. limiter
sensor activated
Manual operation pump...
...Temperature sensor
defective
No voltage behind the internal
safeguard for ZM5311 burner
output
Table 7 Unit troubleshooting
28
Effect on the control characteristics Cause
Heating of DHW is stopped. Current
DHW temperature is below 40 °C.
Thermal disinfection has been
aborted.
Boiler is operating in accordance with
the specifications in manual operation
 Chapter 3.7.3, page 13.
Control operates for max. 30 minutes
with higher flow temperature
 Chapter 3.7.2, page 12.
The boiler heats until the high limit
safety cut-out is triggered.
–
Depending on the faulty sensor.
Burner is not going into operation.
• The set DHW temperature is set
incorrectly.
• The time program has been set
incorrectly.
• The DHW temperature is not rising. ▶ Check whether the DHW circuit is
• The output of the heat source is
insufficient, e.g. because other
heat consumers (e.g. heating
circuits) demand heat during
thermal disinfection.
• The temperature sensor is
incorrectly connected or faulty.
• The cylinder primary pump is
incorrectly connected or faulty.
• FM-MW module or control unit is
faulty.
• The draw-off quantity during
thermal disinfection is too high.
• Manual operation activated
• Flue gas test is active
• High limit safety cut-out position
test was carried out.
• A manual mode was activated.
• Internal safety device of burner has
triggered.
• Current consumption by the
burner is too high.
Remedy
▶ Adjust the set DHW temperature.
▶ Reprogram the
time program.
in automatic mode.
▶ Phone Service.
▶ Select the time for thermal
disinfection so that there is no
overlap with additional heat
demands.
▶ Phone Service.
▶ Deactivate manual operation
 Chapter 3.7.3, page 13.
▶ Deactivate flue gas test
 Chapter 3.7.2, page 12.
▶ Release the key and
key.
▶ Reset control with
 Chapter 3.7.1, page 12.
▶ Deactivate manual operation.
▶ Phone Service.
▶ Phone Service.
Control 8311/8313 – 6720859790 (2020/02)