An alternate system runs on the fog or fine mist injected into the intake air stream. Although a number of commercial systems are available, growers can assemble and install their own system utilizing a high pressure piston pump and fog nozzles. The basic components are demonstrated in Fig. 1. A two-stage system managed by a two- stage thermostat enables more water to be applied on excessively warm, shiny days. Temperature settings ought to be 5-10°F apart.
Algae development in the pads can become a problem that may reduce the effectiveness of the system and lead to accelerated deterioration of the pads. The addition of an algaecide to the drinking water supply will help in control.
It is desirable, especially in hard water areas, to include a Greenhouse Auto Vent wetting agent to the water to obtain additional uniform wetting of the pads. A commercial material or liquid home detergent at the rate of 2 tablespoons per 100 gallons may be used.
Drinking water for the pads ought to be clean and low in mineral content to avoid clogging and coating of the pads. A pump, pipes and gutters are used to recirculate the drinking water. A flow rate 113 gallon per minute per linear foot of pad system ought to be provided to ensure adequate wetting.
In the most common cooling system (fan and pad), the fans draw air through wet pads that lengthen the length of 1 endwall or sidewall. Aspen and coated cellulose are normal pad materials that usually have life of 1 to 3 years. Approximately one sq . foot of pad are is necessary for 20 square feet of floor area.