I would rate vaillant and worcester, including buderus, as the best wiht the exeption of bottom range models that have limited controls and no plate heat exchanger. they tend to get more hammered than the bigger ones and also seem to be exclusively used by installers who like to cut corners.
I will not install:
sauniers are not as bad as they used to, but still would not have one. sorry, forgot to add alpa to my list.
the short story is: like most things, the cheap ones are not the same quality as the those that cost a bit more. i am still waiting for japanse boilers to compete with the german ones.
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