Andrews A17 Fault Code: Causes, Fixes & Repair Costs
What does the Andrews A17 fault code mean?
On Andrews commercial water heaters, fault codes beginning with the letter 'A' denote a lockout condition — a hard shutdown where the appliance has cut out and requires a manual reset before it will attempt to fire again. The number that follows the 'A' identifies which burner module has locked out, so A17 indicates a lockout on burner module 17. The underlying reason for the lockout — whether ignition failure, flame loss, a flame-sensing fault, or another safety trip — is determined by the appliance's Honeywell-based integrated control system and may vary slightly between Andrews ranges such as the MAXXflo, HiFlo EVO, and ClassicFlo. In plain terms: the appliance has detected an unsafe or abnormal condition on that burner module and shut it down to protect the installation. It will not restart automatically; a qualified engineer must establish the cause before the reset is used.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Ignition failure on burner module 17 Common
The most frequent cause of an A-series lockout. The burner attempts to light, but the control board receives no confirmation that ignition has been established within the permitted trial-for-ignition period and shuts the module down. This can stem from a worn ignition electrode, a degraded ignition lead, incorrect electrode gap, or a gas supply interruption to that module.
- Flame-sensing fault Common
The flame sensor (ionisation probe) monitors whether a stable flame is present after ignition. If the probe is coated in combustion residue, is cracked, or has developed a high resistance to earth, it will fail to pass the small ionisation current the control board expects, causing a safety lockout even if the burner did actually light. Regular servicing is supposed to catch this before it causes repeated lockouts.
- Flue or combustion-air restriction Sometimes
Andrews commercial water heaters rely on correct flue draught and adequate combustion air. A partially blocked flue terminal, a collapsed flue liner, or poor ventilation in the plant room can starve the burner of air or prevent safe removal of combustion gases, causing the appliance to lock out as a safety measure.
- Scale or sediment affecting heat exchanger performance Sometimes
In hard-water areas, limescale accumulation inside the heat exchanger reduces heat transfer and can cause localised overheating. Some Andrews models will lock out when an overheat thermostat trips as a result. This tends to develop gradually and is more common on units that have not been descaled or serviced at the manufacturer-recommended intervals.
- Gas valve or gas supply fault Rare
A faulty or sticking gas valve, a drop in gas supply pressure, or an isolation valve that has been partially closed can prevent adequate gas flow to burner module 17, resulting in a lockout after a failed ignition attempt. This is a less frequent but serious cause that an engineer will rule out during diagnosis.
- Control board (PCB) fault Rare
If the integrated control board is failing — due to age, moisture ingress, or component failure — it may misread sensor signals or fail to drive the ignition sequence correctly, producing spurious lockout codes. On older or heavily used commercial units this becomes more plausible, but it is usually only confirmed after all other causes have been eliminated.
How to fix it
- Check that the gas supply to the building and to this appliance is fully on DIY safe
Confirm that the main gas meter isolation valve is open and that any local isolation valve feeding the Andrews water heater has not been partially or fully closed — for example, by maintenance staff working elsewhere in the building. If other gas appliances in the same area are working normally, the supply is unlikely to be the issue.
- Note the exact fault code displayed and the model and serial number DIY safe
Before doing anything else, photograph or write down the code shown (it should alternate between 'A' and '17' on the display), the model name, and the serial number from the data plate. Fault code definitions and the specific burner-module layout vary between the MAXXflo, HiFlo EVO, and ClassicFlo ranges, so this information is essential when calling Andrews technical support or a specialist engineer.
- Attempt a single reset via the control panel reset button DIY safe
Andrews A-series (lockout) codes can be cleared using the control panel reset button — only the locked-out module is reset. Press the reset button once and observe whether the burner module relights and continues to run. If it locks out again within a short time, do not keep resetting repeatedly; persistent lockouts indicate an underlying fault that must be diagnosed before further reset attempts. Do not open the casing or touch any internal components.
- Contact Andrews Water Heaters technical support DIY safe
If the reset does not clear the fault, or if the appliance locks out again quickly, call Andrews Water Heaters on their technical helpline before booking an engineer. Their technical team can often narrow down the likely cause for a specific model when given the fault code, module number, and serial number, which saves diagnostic time on site.
- Book a Gas Safe registered engineer with commercial water heater experience Gas Safe engineer
All service and repair work on Andrews commercial water heaters must be carried out by suitably qualified personnel — Gas Safe registered and ideally familiar with Andrews or Honeywell-controlled commercial hot water systems. The engineer will carry out a full safety inspection of burner module 17, check the ignition electrode and lead, clean or replace the flame sensor, inspect the flue and combustion air supply, verify gas valve operation and supply pressure, and check for overtemperature trips caused by scale. Only genuine Andrews replacement parts should be used. Do not attempt any internal repair yourself.
Parts you may need
- Ignition electrode (burner module) · from £45
- Flame sensor / ionisation probe · from £35
- Ignition lead / HT lead · from £25
- Overheat thermostat / high-limit stat · from £40
- Gas valve (Honeywell or equivalent) · from £220
- Control PCB (model-specific) · from £320
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £150–£450, depending on the underlying cause.
Frequently asked questions
What does the 'A' in A17 mean on an Andrews water heater?
On Andrews commercial water heaters, the letter 'A' in a fault code stands for a lockout fault — the appliance has shut down a specific burner module and will not restart automatically. The number (17 in this case) identifies which burner module has locked out, not the type of fault. Compare this with 'E' codes, which are blocking faults that prevent operation but may clear once the underlying issue is resolved. An A-series lockout always requires a manual reset via the control panel button, and should only be reset after a qualified engineer has established why the lockout occurred.
Can I reset the Andrews A17 fault myself?
You can press the control panel reset button once to attempt a reset — this is the only action that is safe and appropriate for a non-engineer. If the appliance restarts and runs normally, monitor it closely over the next day or two. However, if it locks out again, do not keep pressing reset repeatedly. Persistent lockouts mean the root cause has not been resolved, and repeated reset attempts without diagnosis can mask a developing safety issue. At that point you need a Gas Safe registered engineer who has experience with commercial water heaters.
How much does it typically cost to repair an Andrews water heater showing a lockout fault?
For the most common causes — a dirty flame sensor, a worn ignition electrode, or a faulty ignition lead — you would typically expect to pay somewhere between £150 and £450 including callout, labour, and parts. If the fault turns out to involve a gas valve or a model-specific PCB, costs can climb considerably higher, sometimes £500 or more, particularly if specialist parts need to be ordered in (which may mean two engineer visits). Having a service contract in place for a commercial Andrews installation is usually more cost-effective in the long run than one-off emergency repairs.
Does the A17 code mean the whole water heater has shut down?
Not necessarily. Andrews commercial water heaters, particularly multi-module units like the MAXXflo, are designed so that individual burner modules can lock out independently. If your installation has multiple modules, the remaining modules may continue to provide hot water at reduced capacity while module 17 is locked out. This is one advantage of modular commercial systems. However, you should still arrange for the fault to be diagnosed and rectified promptly — running on reduced modules increases the load on remaining burners and may not meet the hot water demand of a hotel, school, or leisure centre.