What does the Worcester Bosch D4286 fault code mean?

Your boiler has shut down because it thinks the water returning to the unit is dangerously hot, which usually means water isn't circulating through your radiators properly.

How much does it cost to fix Worcester Bosch error code D4286?

Typical repair cost for the Worcester Bosch D4286 fault is £180-450 including labour.

Can I fix Worcester Bosch fault code D4286 myself?

Check that all radiator valves are fully open.

Worcester Bosch D4286 Fault Code: What It Means & How to Fix It

Technical description

The boiler return temperature sensor has detected a return temperature higher than 105°c

What causes this fault?

This fault occurs when water is trapped inside the heat exchanger and cannot move away, causing it to overheat almost instantly. The most common reason is a failed internal circulation pump or a significant blockage in the system pipework that has stopped the flow of water entirely.

This fault often appears during the first cold spell of autumn when heating systems are switched back on after being idle all summer, which can cause internal pump components to seize.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Your boiler has shut down because it thinks the water returning to the unit is dangerously hot, which usually means water isn't circulating through your radiators properly.

Technical description

What causes this fault?

Engineer required

Related guides you might find useful

Radiators cold at the bottom

Banging / kettling / whistling noise

Boiler keeps cutting out

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