Vaillant ecotec plus 831 noises and codes

28 Feb 2007
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United Kingdom
A few days ago, our boiler (Vaillant ecotec plus 831) started making rattling noises. We called a plumber, who replaced the water sensor and removed some grit found in the pump (the central heating system was power flushed a few months ago).

The boiler now makes a noise similar to a compression engine when working and has shown a string of maintenance codes (in no particular order): S.0 (with a humming sound), S.53, S.54, S.97, S.98 and F.75. I have posted a video here:

What could the problem be?

PS. I've just tried to get some hot water: I got a S.97 then a F.75. Switched off and on again: S.54. Turned off and on again: S.98 with a humming sound...
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There seem to be some holes in what you have said, are you an Emmentale cheese?

You have not said how old the boiler is and how long the warrantee was stated to be ( and if you have complied with the condition that it should be serviced annually to preserve the warrantee.

The system should be power flushed BEFORE the new boiler is fitted. It sounds as if yours was flushed later and thats usually because there was a flow or sludge problem.

That sludge will rapidly wear the plastic bearings in Wilo pumps. Most manufacturers will not cover pumps which have work as a result of dirt in the system. However, Vaillant have now changed back to Grundfoss pumps which have very hard ceramic bearings and are less susceptable to wear. There is some evidence that Vaillant will often replace a worn Wilo pump under the warrantee.

Thanks for your responses.

The boiler was installed just over 3 years ago, was serviced annually and was under manufacturer's warranty for 2 years. Yes, the system was powerflushed after the boiler was installed (the plumber who installed the boiler didn't offer or suggest one, it's only last year when some rubber connection tubes burst that it was suggested we get the system cleaned).

This morning, I tried to turn it on again but got the same codes:

S.97: Water pressure sensor check is running, demand (DHW
or heating) is blocked

S.98: Flow-/Return-sensor check is running, demand (DHW or
heating) is blocked

F.75: No pressure rise was detected on turning on the pump - Water pressure sensor or/and pump defective
Air in the heating system, quick bleeder defective
Too little water in appliance; check adjustable by-pass; connect
external expension vessel to return

So, a new pump then? Would any other measures be advisable to prevent the problem of happening again (such as a Magnaclean)?
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Right. Someone came to replace the pump. By doing so, water leaked everywhere! The pump is in but one valve, the pressure relief valve (on the right of the pump) is supposedly leaking. The boiler is still not working.

A few questions: how long does it normally take to replace a pump? What measures has the engineer got to take before and after the replacement (checks, water purge, etc.)? If water leaks when changing the pump, what might have happened? Generally speaking, how difficult/different is it to replace a pump compared to other makes or models?

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