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Gas Works

Valiant Boiler F81/F91 fault code

Anonymous user 23/02/2024 - 3.23 PM

Hi, Every few days I get the F81/F91 daily code on my valiant boiler. The central heating is fine but the hot water stops working. When I reset the boiler this brings the hot water back. Every week the pressure of the boiler rises to about 3.0 bar in the red zone. Is this fixable or is the boiler knackered? Thanks, Bhav

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4 Answers

Anonymous user

From what you have described it sounds like an issue with the pump on the hot water storage. As for the pressure, that can be attributed to an issue with the expansion vessel or a blockage. Both issues can be repaired and it would not be worth replacing the boiler.

Answered9 July 2020

Priory plumbing and heating

No reviews yet

Macclesfield

You could turn the pre heat off by turning the dial anti clockwise until C disappears then turn dial back and that is a temporary fix to stop it from going into fault Could be the shunt pump NTC sensor or a number of things Like previous answer issue with the vessel causing pressure fluctuations Get an appointment booked with an engineer

Answered5 June 2019

John Watson Boiler Services

Rating: 5 out of 5

Banchory

Hi All of the above advice is sound. I would like to add there may be a blockege in the Domestic Heat Exchanger. The pressure rise may be the vessel bladder or pipe restriction. All can be repaired. 😉😁

Answered7 June 2019

C M Hume Gas Services Limited

Rating: 4.9 out of 5

Ayr

Your fault codes are linked to temperature sensors, possible boiler overheat or faulty ntc sensors. Pressure issue could be top-up valves not fully closed or pressure vessel issue , which would normally show when boiler on for a while ie when CH being used. All should be repairable

Answered9 June 2019