An alternate system runs on the fog or great mist injected in to the intake air stream. Although several commercial systems are available, growers can assemble and install their own system using 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 employed on excessively warm, bright days. Temperature settings should be 5-10°F apart.
Algae growth in the pads can become a problem which will decrease the effectiveness of the machine and result in accelerated deterioration of the pads. The addition of an algaecide to the drinking water supply can help in control.
It really is desirable, especially in hard water areas, to add a wetting agent to the drinking water to obtain additional uniform wetting of the pads. A commercial Greenhouse Exhaust Fan materials or liquid home detergent at the price of 2 tablespoons per 100 gallons may be used.
Drinking water for the pads ought to be clean and lower 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 per minute per linear foot of pad program ought to be provided to assure adequate wetting.
In the most common cooling system (fan and pad), the fans draw air through wet pads that extend the length of 1 endwall or sidewall. Aspen and coated cellulose are normal pad materials that usually have life of one to three years. Approximately one square foot of pad are is needed for 20 square feet of floor area.