High
02 on Viessmann Vitodens 111-W

Your boiler has shut itself down as a safety precaution because it has detected an overheating issue within the system.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

What the manual says

Manufacturer manual

Burner control switches to lockout

From this model's manual
Verified against the Viessmann Vitodens 111 W installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

What causes this fault?

This fault occurs when the water inside the boiler reaches an unsafe temperature, triggering a safety sensor to cut the power to the burner. The most common reasons include a failing pump that isn't moving water away from the burner quickly enough, or a buildup of debris and sludge that is restricting flow through the heat exchanger.

This issue often surfaces during the first cold spell of autumn when the heating is turned back on after sitting 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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