Waterside economizers can be expensive to install but are sometimes the only option, especially when dealing with unitary systems, data centers, or other process loads. The installation of an airside economizer system is usually straightforward as long as there is direct access to the outside for air intake and exhaust. However, if given a choice, which system offers the most bang for the buck? Is the answer to this question different for different climates? One way to determine these answers would be to compare the operation of each economizer type for an identical application in a wide range of climates.
Here are the ground rules: The model consists of a 50,000-cfm air-handling system with a minimum outdoor air volume setting of 10% of the total airflow or 5,000 cfm. The system operates 24/7. The overall cooling efficiency is 1.25 kW/ton. The electric rate is $0.075/kWh. The space temperature is maintained at 75 degrees F and the supply air temperature setpoint is 55 degrees. The wet bulb temperature threshold to activate the waterside economizer is 40 degrees. Also, there is a latent heat (moisture) gain from 200 people located in the space served by this system.