F codes are blocking faults, A codes are fault codes, however A or F may be displayed in front of any number, it is the number that is most relevant and the tests followed will be the same for each.
| F CODE | DESCRIPTION | A CODE | DESCRIPTION |
| F07 | High fume temperature | A01 | No burner ignition |
| F10 | Flow sensor fault | A02 | Flame detected with the burner off |
| F11 | Return sensor fault | A03 | High limit protection |
| F12 | DHW sensor fault | A04 | Flue gas fault |
| F13 | Exchanger probe fault | A05 | Fan problem |
| F14 | Flow sensor fault | A06 | No flame after the ignition phase (6 times in 4 minutes) |
| F15 | Fan problem | A41 | Flow sensor disconnected |
| F34 | Supply voltage under 170V | A42 | Flow sensor fault |
| F35 | Irregular mains frequency | A44 | DHW temperature sensor not connected |
| F37 | Incorrect system water pressure | A61 | PCB fault |
| F43 | Exchanger protection activation | A62 | No communication between controller and gas valve |
| F47 | Water pressure sensor fault | A63 | PCB fault |
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| F50 | High limit protection in CH | A65 | PCB fault |
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| F52 | Flow sensor fault |
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| F64 | PCB fault |
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| F66 | PCB fault |
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