The ballast sets and holds the current the ultraviolet lamp arc runs at. A ballast drifting out of specification changes delivered UV-C output without failing outright, so the plant keeps running and quietly under-doses. Match the ballast to the lamp rating actually installed rather than to the reactor model alone. This is the DVG 200 electronic ballast, rated 60–100 W on a 230 V 50 Hz supply and carrying TÜV/UVN approval. On an approved installation the approval attaches to the specified component, so a general-purpose substitute of the same electrical rating is not equivalent. Confirm both the lamp wattage and the supply voltage against the existing unit before ordering. Wedeco was founded in Herford, Germany in 1976 and is now a Xylem brand.