Buderus 800 - Page 41

Servicing 5
Wall-mounted condensing gas boiler Buderus 800 - Subject to modifications resulting from technical improvements!
41
Code Meaning
2P Safety sensor rises faster than 5 °C/sec., blocked for 30 sec.
Possible
cause
Action
1 Resistance in the installation is too high Check if not all (thermostatic) radiator valves are closed or
clogged with dirt
2 Safety sensor is dirty or faulty Check the safety sensor for dirt. Measure if resistance over
the sensor is correct. If not replace safety sensor by
temporarily with another one (see subsection 5.3.9 and
subsection 5.3.10)
3 External domestic hot water tank is too small for the
boiler's capacity
Top up the system (see subsection 2.1.1)
Code Meaning
2U Temperature difference between the flow and return sensors is too high, blocked for 30 sec.
Possible
cause
Action
1 Resistance in the installation is too high Check if not all (thermostatic) radiator valves are closed or
clogged with dirt
2 Problem with the pump or pump cabling
(no circulation)
Check if the pump cabling is faulty or if the pump is stuck
(see subsection 5.3.7)
3 Water pressure is too low in the system Top up the system (see subsection 2.1.1)
4 Return sensor is defective or the cabling is faulty Measure the resistance of the sensor
(see subsection 5.3.12)
Code Meaning
4A Flow sensor exceeds 100 °C
Possible
cause
Action
1 Flow sensor is dirty or faulty Check the sensor, replace if necessary
(see subsection 5.3.9 and subsection 5.3.10)
2 There is a problem with the pump or pump cabling
(no circulation)
Check if the pump cabling is faulty or if the pump is stuck.
Replace pump if necessary (see subsection 5.3.7 and
subsection 5.3.8)
3 Water pressure is too low in the installation Top up the system (see subsection 2.1.1)
Code Meaning
4C F2 fuse malfunction, or flue gas thermostat active
Possible
cause
Action
1 Water pressure is too low in the installation Top up the system (see subsection 2.1.1)
2 Heat exchanger is dirty Check for a dirty heat exchanger and clean if necessary
(see subsection 4.1)
3 Flue gas retarder faulty or missing Check if the flue gas retarder is installed in the heat
exchanger