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We did some maintenance on a Viessmann Vitodens WB 2 8-32 that we installed 16 years ago. Part of it was cleaning out the HX which seems particularly dirty. The condensate trap had a lot of corrosive particles (see the bucket picture) and the Gianoni coils had quite a bit of built-up corrosion, so much so that I didn't want to go at it with a credit card or even CLR.
My question is: Is this an indication of a failing HX?
Often wrong, never in doubt.