Short answer
Andrews MAXXflo water heaters show A codes for lockouts (reset with the reset button once fixed) and E codes for blocking faults (which need a repair before they clear). A01 is three failed ignitions, A02 an overheat with no water flow, A24 too many flame failures, and E41 live and neutral reversed.
Multiple burner modules
The display alternates the letter and the burner module number. With faults on more than one module it cycles every 5 seconds, and reset only clears the module currently shown.
Before you reset
A single reset after a power cut or a known one-off event is reasonable. Repeated resets are not: many commercial controls count resets and lock out further (for example a 'too many resets' code), and resetting a flame or gas valve fault over and over can mask a dangerous condition. If a lockout returns, isolate the appliance and call a Gas Safe registered engineer with the relevant commercial competence.
Andrews MAXXflo fault codes
| Code | Meaning | What to check |
|---|---|---|
| A01 | Three failed ignitions — still no flame detected after three ignitions | — |
| A02 | Overheat stat failure — no water flow, flow sensor not detecting a temperature rise | — |
| A03 | The two flow sensors differ by more than 10°C for more than 60 seconds | — |
| A05 | Gas valve relay error — relay not switching correctly | — |
| A06 | Safety relay error — relay not switching correctly | — |
| A08 | Fan error — fan not reaching target speed for more than 60 seconds | — |
| A09 | Control error: internal storage location | — |
| A10 | Stored parameter contents not correct | — |
| A11 | Flow temperature went above 95°C | — |
| A12 | Stored contents do not match the software version | — |
| A14–A19 | Control error: internal storage location | — |
| A20 | Flame still present 10 seconds after the gas valve has closed | — |
| A21 | Flame detected before the gas valve opened during start-up | — |
| A24 | Too many flame failures — flame failed three times in one burn cycle | — |
| E0 | Read error: not able to read stored parameters (slave board) | — |
| E09 | Control error: internal RAM location not correct | — |
| E12 | Incorrect parameters programmed in the slave board | — |
| E13–E16 | Control error: AD-circuit reference measurement out of range | — |
| E18 | Control error: internal RAM | — |
| E19 | Control error: not able to read parameters | — |
| E20 | No slave board present | — |
| E22 | Power fault: 50 Hz supply deviation too large | — |
| E28–E31 | Control error: AD-circuit reference measurement (slave board) | — |
| E33 | Flame detected when gas valve was closed | — |
| E41 | Phase error: live and neutral reversed | — |
| E42 | Phase error: supply frequency deviation too large | — |
| E44 | Control error: poor communication between the two processors | — |
| E47 | Return sensor open circuit | — |
| E48 | Flow sensor open circuit | — |
| E60 | Tank sensor open circuit | — |
| E63 | Return sensor short circuit | — |
| E64 | Flow sensor short circuit | — |
| E65 | Return sensor open circuit (master board) | — |
| E70 | Tank sensor shorted | — |
| E75 | Return sensor shorted | — |
| E78 | Reset error: too many user resets | — |
Source: Andrews MAXXflo installation manual (2016). Codes and meanings can differ between versions and control software — always check the manual for your exact appliance.
Figures are typical for UK natural gas. The current edition of the relevant IGEM standard and the manufacturer's instructions always take precedence on site.
Need this done on site?
Need a commercial gas engineer in London?
Gas Safe registered commercial engineers, 24 hours a day. Call now or book online and we'll confirm a time.