Buderus 600 - 11S Installation And Maintenance Instructions Manual page 38

5 Servicing
Code Meaning
3C
Bad plug-in connection at cable harness, or damaged wiring
Possible
cause
1 Cable harness is faulty
2 Connectors at the back of the UBA are loose or faulty
3 UBA might be faulty
Code Meaning
4A
Flow sensor exceeds 100 °C
Possible
cause
1 Flow sensor is dirty or faulty
2 There is a problem with the pump or pump cabling
(no circulation)
3 Water pressure is too low in the installation
Code Meaning
4C
F2 fuse malfunction, or flue gas thermostat active
Possible
cause
1 Water pressure is too low in the installation
2 Heat exchanger is dirty
3 Flue gas retarder faulty or missing
4 Heat exchanger has a problem
Code Meaning
4F
Flow sensor exceeds 100 °C
Possible
cause
1 Resistance in the installation is too high
2 Heating capacity is too large for the installation
3 Safety sensor is faulty
4 Problem with the pump or pump cabling (no circulation)
5 Water pressure is too low in the installation
Code Meaning
4H
System error
Possible
cause
1 Boiler is in operation for DHW due to a dripping faucet
Buderus • http://www.buderus-domestic.co.uk
38 Installation and maintenance instructions for wall-mounted condensing gas boiler 600 - 11S/19S/24S/24C • 02/2006
Action
Check cable harness for faults and bad connections
Check the connectors at the back of the UBA
Check the UBA by temporarily connecting an other UBA
(see subsection 5.3.3)
Action
Check the sensor, replace if necessary (see subsection
5.3.14, subsection 5.3.15, subsection 5.3.16)
Check if the pump cabling is faulty or if the pump is stuck.
Replace pump if necessary (see subsection 5.3.9 and
subsection 5.3.10)
Top up the system (see subsection 2.1.1)
Action
Top up the system (see subsection 2.1.1)
Check for a dirty heat exchanger and clean if necessary.
(see subsection 4.1)
Check if the flue gas retarder is installed in the heat
exchanger
Purge heat exchanger
Action
Check if not all (thermostatic) radiator valves are clogged
with dirt
Adjust the heating capacity
Check the sensor and measure if resistance over the
sensor is correct. If not replace safety sensor (see
subsection 5.3.11, subsection 5.3.12, subsection 5.3.13)
Check if the pump cabling is faulty or if the pump is stuck
(see subsection 5.3.9)
Top up the system (see subsection 2.1.1)
Action
Check for dripping faucets
Subject to modifications resulting from technical improvements!