Ideal c35 FU fault

27 Mar 2021
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United Kingdom

I am posting here in the hope that someone with knowledge of this particular fault may be able to help me.

Having moved in to a new build 3 years ago our ideal c35 boiler has started to display a fault and in turn prevented us from having any hot water. In fact this started almost a year ago and after having various visits from engineers and still no real answer I find my self searching for answers online.

The fault displayed is the “FU” type which according to ideal is a “water circulation issue. This signifies that there could be an airlock or blockage within the system”. When this first appeared we called a local engineer who found that the heat plate had become blocked with particles from within the system and advised us that it needed to be rinsed/replaced in order to rectify. This was done and we returned to having hot water for around a month before the fault code reappeared.

On the second visit the engineer “flushed” the system and once again washed the plate whilst also fitting a magnasafe filter in the hope of preventing the particles from reaching the boiler in the first place. Again this rectified the problem, this time for around 5 weeks before yet again the code reappeared.

In order to get a second opinion we then contacted ideal who most recently came out and replaced what we believe to have been the heat plate, but further advised that it was an installation issue rather than a boiler fault as such due to the brown colour of the water (most recently believed to have just been the colour of the system inhibitor previously used). This again provided us with hot water but only for 2 days which brings me up to today where yet again I am left without hot water.

I am hoping someone can provide some clarity on exactly what could be causing this to happen. The fault can sometimes be cleared and water can be run, albeit at a lower pressure. The radiators have been bled, do not have cold spots and the central heating does not seem to produce the same fault. Strangely more often than not it seems to throw up the fault when using the bath tap (perhaps due to the higher pressure)?

I have just checked the magnasafe filter and it is pretty clogged up with sludge which to me doesn’t seem right on such a new installation?

Is this something that could have been done incorrectly when the boiler was installed? Why would it only start to happen after 2 years of use?

I hope someone may be able to help me and my family. TIA.
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