An alternate system uses a fog or great mist injected in to the intake air stream. Although a number of commercial systems can be found, growers can assemble and install their own system using a high pressure piston pump and fog nozzles. The basic 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 ought to be 5-10°F apart.

Algae development in the pads may become a problem which will reduce the effectiveness of the system and lead to accelerated deterioration of the pads. The addition of an algaecide to the drinking water supply can help in control.

It is desirable, especially in hard drinking water areas, to add a wetting agent to the drinking water to obtain more uniform wetting of the pads. A commercial material or liquid home detergent at the rate of 2 tablespoons per 100 gallons may be used.

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 accustomed to recirculate the drinking water. A flow rate 113 gallon each and every minute per linear foot of pad program ought to be provided to assure adequate wetting.

In the most typical cooling system (fan and pad), the fans draw air through wet pads that extend the length of one endwall or sidewall. Aspen and coated cellulose are normal pad materials that usually have life of 1 to three years. Approximately one square foot of pad are is necessary for 20 square ft of floor area.

For additional information on Greenhouse Exhaust Fan, see our internet site.