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Ideal fault code

Ideal F5: return thermistor fault

Engineer only

Ideal describes F5 on Logic Combi (ESP1) boilers as: return thermistor fault.

What you can safely do

There is nothing you can safely do yourself with this one. Leave the boiler off and book an engineer.

Find a Gas Safe engineer near you Opens the official Gas Safe Register search.

Applies to: Logic Combi (ESP1). Codes can differ between models, so check your manual.

From Ideal's own fault tables. Your model name is usually on the front of the boiler or in the user manual.

Model	Meaning
Logic Combi (ESP1)	Return thermistor fault

Can I fix Ideal F5 myself?

No. It needs a Gas Safe registered engineer to diagnose. Tell them the exact code and your boiler's model name.