Baxi 600 Combi 2 A.02.46 warning: device priority error

If your Baxi 600 Combi 2 shows A.02.46, Baxi describes the warning as “Device priority error”. The wording sounds abstract because it relates to how the boiler recognises and coordinates connected functions or controls. It does not name a failed part.

The boiler may still provide some heating or hot water, or it may not respond normally to a request. What you notice depends on the controls and accessories fitted to your particular system. Record the complete code, including every dot, because nearby Baxi codes have different meanings.

What does Baxi warning A.02.46 mean?

Baxi lists A.02.46 as “Device priority error” for its Combi 2 and System 2 boiler group. The Baxi 600 Combi 2 is included in that group, so the official meaning applies to this model.

In plain English, the boiler has encountered a problem deciding how one or more recognised devices or functions should be prioritised. Heating systems can use controls that ask for heat at different times. The warning indicates that the expected priority arrangement is not being handled correctly.

The display does not identify which device is involved. It also does not prove that a thermostat, programmer, receiver, boiler control, or other accessory has failed. A qualified engineer needs to compare the boiler’s settings with the equipment actually installed before deciding what needs attention.

What might you notice at home?

You might find that the boiler does not respond to a normal heating request, that one demand appears to override another unexpectedly, or that operation becomes intermittent. In some homes the warning may appear while heating and hot water still seem available.

Because the Baxi 600 Combi 2 produces heating and hot water from one appliance, the timing of the warning can be useful. Note whether it appeared when a hot tap was opened, when the heating schedule started, or while a room control was being adjusted. This does not identify the cause, but it gives the engineer a clearer picture of the circumstances.

Safe checks you can make

Keep your checks to the user-facing displays and controls you normally operate. You can safely collect the following information:

• Photograph or write down A.02.46 exactly as displayed.
• Note whether central heating, hot water, or both are affected.
• Look at any separate programmer, thermostat, or receiver without opening it and record what its screen or indicator shows.
• Remember whether the warning began after a power cut, control replacement, service visit, or other recent work.
• Record whether the warning is constant or appears only when a particular function is requested.
• Write down the boiler model and the names of visible controls.

If a room control is not communicating, our guide to a thermostat not talking to the boiler covers safe external observations. However, A.02.46 does not confirm a thermostat problem, so do not replace or reconfigure a control based on this warning alone.

What should you not do?

Do not remove the boiler casing, open a receiver, touch terminals, bridge contacts, alter polarity, or test voltage, resistance, or continuity. Do not enter installer menus or change priority and configuration settings found in online discussions. A setting that looks simple may affect how the boiler responds to several demands.

Avoid repeated pairing attempts or factory resets on connected controls unless the user guide for the exact control explicitly tells you to do so for this situation. Resetting devices can remove useful settings and make the original problem harder to reproduce.

Should you reset the boiler?

One normal user reset can be reasonable only if the Baxi user guide for your exact boiler permits it and you can use the external control without opening anything. A reset may clear a short-lived interruption after a power event.

If A.02.46 returns, stop resetting the appliance. A recurring priority error needs professional testing. Repeated resets do not correct an incompatible setting, interrupted connection, or faulty component, and they can obscure the pattern that helps locate the problem.

What can cause a device priority error?

The verified code description supports broad categories rather than one certain cause. The boiler may be seeing connected devices in an unexpected arrangement, a control or accessory may not be communicating as configured, or stored settings may not match the installation. A connection or component issue is also possible.

These possibilities are not a parts list. The same code can arise in installations with different control arrangements, and the visible device is not necessarily the source of the error. Professional checks should establish the fitted equipment and expected priority before anything is replaced.

What will a qualified engineer check?

An engineer can identify the controls and accessories connected to the system, confirm which functions the boiler is configured to recognise, and test whether requests are being received and handled correctly. They can inspect relevant connections and settings using Baxi’s technical information.

Once the actual mismatch or failed element is confirmed, the engineer can correct the configuration or repair the affected equipment and then test normal heating and hot-water operation. Internal boiler and control work is not suitable for a householder, so keep all casings closed.

When should you arrange a repair?

Arrange professional help if A.02.46 returns after one permitted reset, if heating or hot water becomes unreliable, or if a control no longer operates the boiler. An intermittent warning should also be checked, especially when it repeatedly appears during the same demand.

Give the engineer a photo of the code, a list of visible controls, and notes explaining which functions still work. Mention recent power interruptions or changes to the heating controls. This evidence is more useful than guessing which device is responsible.

Gas and carbon monoxide safety

A.02.46 is a device-priority warning. It does not itself confirm a gas leak or carbon monoxide. Treat separate warning signs urgently: if you smell gas, suspect carbon monoxide, hear a carbon monoxide alarm, notice unusual fumes, or see scorching, stop using the appliance, get fresh air, leave when necessary, and follow current Gas Safe emergency advice. Do not rely on the boiler code to decide whether the property is safe.

Quick answers

Is A.02.46 a thermostat fault?

Not necessarily. Baxi’s wording is “Device priority error”, and the code does not identify a thermostat or any other single device.

Can I change the priority setting myself?

No. Avoid installer menus and configuration changes. The settings need to be matched to the equipment fitted and checked by a qualified engineer.

Can the boiler keep working with this warning?

Some functions may continue, but behaviour varies with the installation. Record what works and arrange help if the warning returns or operation is unreliable.

Will one reset clear A.02.46?

It may clear a temporary interruption if the user guide permits a reset. If the code returns, further resets are not a repair.