An alternate Greenhouse Auto Vent system uses a fog or great mist injected in to the intake air stream. Although many commercial systems can be found, growers can assemble and install their own system utilizing a high pressure piston pump and fog nozzles. The basic components are proven in Fig. 1. A two-stage system managed by a two- stage thermostat allows more water to be employed on excessively warm, shiny days. Temperature settings should be 5-10°F apart.
Algae development in the pads can 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 water supply will help in control.
It is desirable, especially in hard drinking water areas, to include a wetting agent to the water to obtain additional uniform wetting of the pads. A commercial material or liquid household detergent at the price of 2 tablespoons per 100 gallons may be used.
Water for the pads should be clean and lower in mineral content to prevent 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 program should be provided to guarantee adequate wetting.
In the most common coolant system (fan and pad), the fans draw air through wet pads that prolong the length of one endwall or sidewall. Aspen and covered cellulose are normal pad materials that always have life of one to 3 years. Approximately one sq . foot of pad are is necessary for 20 square feet of floor area.