Viesmann Hot Water Overheating

Hi Blighty. I have a 7-year old Viesmann Vitotronic 100 Type KS2 here in France. This is an oil-fired unit with integral hot water tank, and is bigger than I am - all very un-British - but I hope the control principals are roughly the same.

Recently, the hot water has stopped maxing out at the programmed temperature(60 deg), and carries on until it reaches around 78 deg - the temperature set on the small manual dial on the front - I guess the safety limit. Central Heating is functioning just fine.

I would welcome any suggestions as to the cause (thermocouple? control unit?), so that I can be pre-armed with the facts (in English) before calling in my local installer/maintainer who, although brilliant at his trade, is liable to start by recommending a new boiler. Such is the (occasional) fate of ex-pats with iffy French.

Thanks in anticipation.

Je pense que c'est la meme chaudiere que mon amie Tom en Charente.

C'est possible que le sensor pour l'eau chaude ne marche pas. Vous pouvez measurer la resistance et comparer avec le information dans le livre.

Tony

The Vitotronic is your boiler controls. The boiler will be another name. The KS2 was never sold in the UK and there are probably no English instructions available.