Boiler overheating in hot water mode.

[JackoC]

I have a viessmann vitodens 050-W BPJD. Central heating working as it should however the hot water is getting to high, reaching 90 degrees cutting out to cool down and then starting again. Seems very noisy in hot water mode also. I’m going to clean the plate heat exchanger once the new washers have arrived but just wondering if any one would recommend looking at anything else?

 

[ShaunCorbs]

Test the plate first could be pump