I have a Remeha Advanta plus 28c combi boiler and recently I started having problems with it. First it started locking and E10 appeared (No flow / No water in Boiler / Faulty pump). Called first engineer out and he said t was the heat exhanger and I would be better off changing the whole boiler, which is only 4.5 yrs old. He did my annual service and replaced the ignition (the old was corroded). All was fine except when turning the hot water on there was a mighty clanking sound and the boiler would lock out again, this time showing E7 (No flow / No water in Boiler / Faulty pump). Called second engineer out and after 5 minutes of coming in said I needed a power flush and my expansion vessel replaced because it was damaged by sludge, but he won't replace it unless we have the power flush first.
Now, I am not an expert but certainly the power flush will only clear the central heating system (which is working fine and I don't have cold spots in any of my radiators) and I am not sure it will fix my hot water.
I am not a heating engineer, but like you I do not believe that a power flush will make any difference to your hot water flow, or the loud clanking.
It is unclear from your query if the loud clanking occured immediately after the first engineer had called. If this is the case then he may have left something loose, and you should call him back to rectify this without charge. However, the fact that you called in a second engineer suggests that you were unimpressed with the first one.
If the fault occured sometime after the first service visit, or if you do not want the first engineer back, then look for a locally recommended heating engineer, or maybe contact the manufacturer to arrange a service.
Powerflush is easy money - has anyone tried the fault that the boiler is telling you ? restriction in flow or faulty pump - it seems like an overheat prob and the clanking is likely to be related to sticking pump.
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