An alternate system runs on the fog or great mist injected in to the intake air stream. Although several commercial systems can be found, growers can assemble and set up their own system utilizing a high pressure piston pump and fog nozzles. The essential components are proven in Fig. 1. A two-stage system controlled by a two- stage thermostat enables more water to be employed on excessively warm, bright days. Temperature settings should be 5-10°F apart.
Algae development in the pads may become a problem which will decrease the effectiveness of the machine and lead to accelerated deterioration of the pads. The addition of an algaecide to the drinking water supply will help in control.
It really is desirable, especially in hard drinking water areas, to include a wetting agent to the water to obtain more uniform wetting of the pads. A commercial materials or liquid Greenhouse Exhaust Fan household detergent at the price of 2 tablespoons per 100 gallons may be used.
Drinking water for the pads should be clean and low in mineral content to prevent clogging and coating of the pads. A pump, pipes and gutters are used to recirculate the water. A flow rate 113 gallon per minute per linear foot of pad system should be provided to ensure adequate wetting.
In the most typical cooling system (fan and pad), the fans draw air through wet pads that lengthen the length of one endwall or sidewall. Aspen and covered cellulose are common pad materials that always have life of one to three years. Approximately one square foot of pad are is needed for 20 square feet of floor area.