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. Wedeco Ecoray lamps are low-pressure high-output amalgam lamps matched as a pair to their ballast; using an unmatched lamp or ballast forfeits the efficiency, warm-up and dimming behaviour the pairing exists to provide. This is the Ecoray TDX 30 C1 Dual ballast, a dual-output unit. Match the ballast to the lamp rating actually installed rather than to the reactor model alone. Wedeco was founded in Herford, Germany in 1976 and is now a Xylem brand.