Desert coolers are widely used for cooling rooms in hot countries like India. Conventional coolers have a water tank at the bottom. Water is pumped to the top of the cooler which is allowed to fall on the three walls of the cooler body, the fourth wall having a fan. The fan sucks air through three water wetted walls and blows out. This air is cooler than that of surrounding one.
Water pump remains on to pump the water upward. This consumes power as the pump runs continuously. Power can be saved if on time of pump is reduced. This is done by adding an additional water tank at the top of the cooler body. Water, from existing bottom tank, is pumped to fill the top tank. Top tank supply water to wet the said three walls of the cooler. Hence, level of top tank reduces gradually and reaches minimum limit. Pump starts automatically when level of top tank reaches minimum limit. Pump gets off when level of top tank reaches maximum level limit. A level controller is used to control the pump. This arrangement saves precious electrical energy and extends the life of the pump.