Gasbrenner Gastherme Austausch /Gas burner replacement Rexola biferral

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How to replace gas burner of Viessmann Rexola-biferral RV24 (1991-1995).
One of few durable and very powerful heating systems of 90s, can be still found all over Germany, running flawless if properly maintained. In my cased the gas burner was damaged, therefore I had to replace it with the new (used but still good) one. I hope to gain few more years before switching to another heating system.
Der Biferral ist ein Niedertemperaturkessel, Baujahr 1991 - 1995. Output 19 - 24 kW.