Direct air handlers are a type of cooling system that use outdoor air to cool the data centre. They draw in fresh air from outside, filter it, and supply it to the data centre at the desired temperature and humidity level. Direct air handlers can reduce the energy consumption and operating costs of data centres by eliminating the need for mechanical cooling or refrigeration. However, they also have some challenges and limitations that need to be considered. One of the main factors to consider when using direct air handlers for data centres is the temperature, humidity and contamination of the outdoor environment. Depending on the location and climate of the data centre, the outdoor air may not always be suitable for cooling the data centre. For example, if the outdoor air is too hot, too humid, or too polluted, it may not provide enough cooling capacity, or it may damage the IT equipment or cause corrosion. Therefore, direct air handlers need to have sensors and controls to monitor the outdoor air quality and adjust the airflow accordingly. They may also need to have backup cooling systems or supplementary cooling devices, such as evaporative coolers or heat exchangers, to cope with extreme weather conditions or peak loads.
References: Data Center Cooling: A Comprehensive Guide - Dgtl Infra, Carrier Data Center Cooling System
39DC, Dublin Data Center: Rooftop Air Handlers.