Once I had Viessmann vitopend 100 WH0A water heating boiler. I can't remember much of it that I could share, but I have some pictures. I am almost sure that I have some pictures from inside burning chamber but can't find them at moment. It is a central heating boiler with tap water heating included. This boiler has no accumulating heating tank- it heated water on demand. Once this boiler developed a problem which was the reason I opened it. It did not heat my apartment anymore- it started but quickly stopped its heating cycle. I think mine problem was too much moist/wet air intake at cold nights and not cleaned ignition rods. There were a actual problem code which I cant recall also. Something about getting no reading about temperature I thin- as no burning in chamber.