This ballast has flow control function. It means, that once the flow sensor feel the water flow, the UV lamp will TURN ON.
Once the flow stopped the UV lamp will TURN OFF with small delay.

advantage:
uses less electricity, because the UV lamp works in accordance with the water flow,

will save the life of the UV lamps,

limits the temperature of the in the chamber.

designed for the LUXE 16w, 25w and 55w uv systems

16w comes with 1/2" bsp flow switch

25w comes with 1/2" bsp flow switch

55w comes with 3/4" bsp flow switch