Novus N321S Differential Temperature Controller Solar/Water/Air (12-24V)Great for: Harnessing renewable energy Controlling hot water temperature in solar installations e. g. Swimming Pools, Hot Tubs and Hot Water Recycling hot air in factories, warehouses and agricultural buildings Cooling grain stores to maintain correct differential Includes x 2 NTC sensors The N321S is a controller originally intended for solar water heating applications. It controls liquid or air circulation system based on the difference in