Boiler shuts down and goes to lockout
|faulty pump (not at full capacity)||Check the pump for signs of damage, test the electrical connections, and replace if necessary. Replace pump head|
|faulty fan (not at full capacity)||Check / lubricate bearings|
|clear debris build up||Replace fan assembly|
|blocked condensate pipe work/trap||Clear blockage / ice plug or Increase pipe work fall|
|faulty ionisation electrode||Check gap/wiring /damages|
|blocked heat exchanger (blocked with sludge)||Replace or cleanse system|
|blocked primary filter on plate exchanger||Clean debris from filter|
|faulty thermistor (losing calibration)||Check / replace|
|faulty overheat cut out stat (losing calibration)||Check / replace|
|faulty gas valve (faulty modureg / solenoid)||Replace gas valve|
|blocked bypass pipe/ no bypass||Adjust / install bypass|
|faulty air pressure switch (stuck in NO position)||Replace air pressure switch
Testing the Air Pressure Switch:
Replacing the Air Pressure Switch:
It’s important to note that working on a boiler can be dangerous and should only be carried out by a qualified heating engineer.
Additionally, the specific steps for testing and replacing a faulty air pressure switch may vary depending on the make and model of the boiler, so it’s important to consult the manufacturer’s instructions for specific guidance.
|faulty low water pressure switch (losing calibration)||Replace / clear blockages|
|Low water pressure||Check the pressure gauge and refill the system as necessary.|
|Excess air trapped within heat exchanger||Check / replace air vent. Clean the heat exchanger, inspect the combustion chamber and flue.|
|Blocked condensate pipe||Clear the blockage in the condensate pipe, check the trap and discharge point for debris.|
|Air in the system||Bleed the radiators and boiler to remove any air pockets.|
|Faulty pressure relief valve||Test and replace the valve if necessary.
Testing the Pressure Relief Valve:
Replacing the Pressure Relief Valve:
Additionally, the specific steps for testing and replacing a pressure relief valve may vary depending on the make and model of the boiler, so it’s important to consult the manufacturer’s instructions for specific guidance.
|Faulty printed circuit board (PCB)||Test the PCB for faults and replace if necessary.|
|Faulty thermostat||Test the thermostat and replace if necessary.
To test the thermostat on a combi boiler follow these steps:
It’s important to note that this is not an exhaustive list of all the possible faults and solutions that could cause a combi boiler to shut down.
Other Issues to check
- Noisy Fan
- Noisy Pump
- Noisy Hot Water Flow Switches
- Noisy Solenoid
- Burner Not Igniting
- Boiler Fan Problems
- Boiler Shuts Down
- Explosive Ignition
- Blocked Plate Exchanger
As a member check out these Key Areas
- Sequence of boiler operation
- Boiler servicing procedures
- Boiler System Component Testing
- Top Tips for the Heating Engineer
- Boiler Manuals and Service Manuals
- General Boiler Fault Finding
- Boiler Error Codes
- Using Multimeters to diagnose Boiler Faults