Buderus 800 - Page 42

Servicing5
Wall-mounted condensing gas boiler Buderus 800 - Subject to modifications resulting from technical improvements!
42
Code Meaning
4F Flow sensor exceeds 100 °C
Possible
cause
Action
1 Resistance in the installation is too high Check if (thermostatic) radiator valves are clogged with dirt
2 Boiler capacity is too large for the installation Adjust the boiler’s capacity
3 Safety sensor is faulty Check the sensor and measure if resistance over the
sensor is correct. If not replace safety sensor
(see subsection 5.3.9 and subsection 5.3.10)
4 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)
5 Water pressure is too low in the installation Top up the system (see subsection 2.1.1)
Code Meaning
4L Short circuit in safety sensor
Possible
cause
Action
1 Safety sensor is faulty Check the sensor and measure if resistance over the
sensor is correct. If not replace safety sensor
(see subsection 5.3.9 and subsection 5.3.10)
2 A short or bad connection in the cable harness Check the cable harness and/or connector of the sensor
3 UBA might be faulty Check the UBA by temporarily connecting a different UBA
(see subsection 5.3.5)
Code Meaning
4P Safety sensor has a loose connection or is defective
Possible
cause
Action
1 Safety sensor faulty or disconnected Check the sensor and measure if resistance over the
sensor is correct. If not replace safety sensor
(see subsection 5.3.9 and subsection 5.3.10)
2 A short or bad connection in the cable harness Check the cable harness and/or connector of the sensor
(see subsection 5.3.12)
3 UBA might be faulty Check the UBA by temporarily connecting a different UBA
(see subsection 5.3.5)
Code Meaning
4U Short circuit in flow sensor
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 A short or bad connection in the cable harness Check the cable harness and/or connector of the sensor
(see subsection 5.3.12)