An alternate system uses a fog or good mist injected into the intake air stream. Although many commercial systems are available, growers can assemble and set up their own system using a high pressure piston pump and fog nozzles. The basic components are demonstrated in Fig. 1. A two-stage system controlled by a two- stage thermostat allows more water to be employed on excessively warm, bright days. Temperature settings should be 5-10°F apart.
Algae development in the pads can become a problem that may 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 is desirable, especially in hard water areas, to include a Greenhouse Exhaust Fan wetting agent to the drinking water to obtain more uniform wetting of the pads. A commercial material or liquid household detergent at the price of 2 tablespoons per 100 gallons can 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 guarantee adequate wetting.
In the most typical coolant system (fan and pad), the fans draw air through wet pads that expand the length of 1 endwall or sidewall. Aspen and covered cellulose are normal pad materials that always have life of one to 3 years. Approximately one square foot of pad are is needed for 20 square ft of floor area.