Most boilers stop working due to external factors rather than due to faulty designs. A malfunction must be diagnosed and eliminated, and you can do that using the troubleshooting table below. It describes the most common causes of malfunctions, and there are solutions in the opposite column.
| CODE | CAUSE | ALARM TYPE | ACTION |
|---|---|---|---|
| AL10 | Ignition failure/not flame sensed, condense sensor activated | Final | Reset, check appliance operation |
| AL20 | Limit thermostat fault | ||
| AL21 | External device fault (UHT/CPA) | Reset, check appliance | |
| AL26 | Return temperature too high | Reset, check pump, ensure there is sufficient flow sensor temperature), circulation around heating circuit/s | |
| AL28 | Temperature differential inverted (return sensor temperature higher than flowsensor temperature) | Reset, check pump, ensure there is sufficient circulation around heating circuit/s thermistors | |
| AL34 | Fan tacho signal fault | Reset check appliance operation, check fan | |
| AL52 | Internal fault | Reset, check appliance operation | |
| AL55 | Jumper tag fault | Check jumper tag configuration | |
| AL60 | Temporary | ||
| AL71 | Primary (flow) thermistor fault | Check primary thermistor, check wiring | |
| AL73 | Return thermistor fault | Check return thermistor, check /wiring | |
| AL74 | No water circulation | Final | Reset, check appliance operation, check pump, ensure there is water and sufficient circulation around heating circuit/s |
| AL79 | Flow temperature too high, or temperature differential between primary and return too high | Reset, check appliance operation, check thermistors |
| Fault | Possible causes | Remedy |
|---|---|---|
| Appliance fires then lockouts | Incorrect gas pressure flue blocked or broken | Check incoming pressure and/or burner pressures check flue assembly |
| Appliance wont fire for hot water | Hot & cold pipes reversed flow regulator blocked insufficient flow rate | Check external plumbing remove and clean increase flow rate |
| Appliance wont fire for heating | External control or wiring fault or wiring | Check external controls |
| Appliance fires for heating but no circulation around system | Flow & return service valves closed air in appliance pump stuck | Open service valves open dustcap on ‘aav’ open vent plug on pump and rotate shaft flush system |
| Debris in system | ||
| Appliance inactive no ‘led’s showing | Electrical supply fault blown fuse | Check supply to appliance for 240v between ‘l’ & ‘n’ check and replace |
| ALARM CODE | CAUSE | ALARM TYPE | ACTION |
|---|---|---|---|
| St | AUTOSTOP | Final | Call engineer |
| _CL | CALL FOR SERVICE | Temporary then Final | |
| A01 | Ignition failure, flame not sensed, internal fault | Final | Reset, check appliance operation |
| A02 | Limit thermostat fault | ||
| A03 | Fan tacho signal fault | Reset check appliance operation, check fan | |
| A04 | Insufficient system water pressure | Check/refill system pressure, reset, check appliance operation | |
| A06 | DHW thermistor fault | Temporary | Check DHW thermistor |
| A07 | Primary (flow) thermistor fault | Temporary | Check primary thermistor, check wiring |
| Primary (flow) thermistor over temperature | Temporary then Final | Reset, check appliance operation | |
| Temperature differential | Final | Reset, check appliance operation, check thermistors | |
| A08 | Return thermistor fault | Temporary | Check return thermistor, check wiring |
| Return thermistor over temperature | Temporary then Final | Reset, check appliance operation | |
| Temperature differential inverted | Final | Reset, check pump, ensure there is sufficient circulation around heating circuit/s | |
| A09 | Flue thermistor or flue thermistor counter fault | Temporary | Check flue thermistor counter at power on, check flue thermistor, check wiring |
| Flue thermistor over temperature | Final | Reset, check appliance operation | |
| A77 | Low temperature thermostat fault | Temporary | Check low temperature thermostat |
| Adj | Calibration | Na | None |
| ACO | Service operation | ||
| P | Preheating function active | ||
| P blinking | Preheating function running | ||
| Flame | Flame ON | ||
| Hours | Stand-by | ||
| — | OFF |