High
E08 on Ariston Microsystem 15

Your boiler has switched off because a safety sensor in your underfloor heating system has detected the water is getting too hot and has triggered an automatic shutdown to prevent damage.

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

Under floor heating system safety thermostat contact open (boiler shutdown both in D.H.W. mode and C.H. mode; boiler operation resumes automatically when the thermostat contact closes on cooling).

Shared across the range
This code is shared by the boilers in this range, which use the same control board. It may not be printed in this exact variant’s manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

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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Avoid the next call-out bill

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All 93 fault codes on the Microsystem 15

Seeing a different code? Every code this model can display, in one place.

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