Comparing economizer relief systems

States an outdoor air economizer is a damper arrangement and automatic control system that allows a cooling air handler to supply outdoor air instead of recirculated air to reduce or eliminate the need for mechanical cooling during mild or cold weather. One of the key elements of an economiser is a system to relieve the excess outdoor air supplied to the building when the economiser is enabled. States that without an adequate relief system, the building can become over-pressurised, causing exterior doors to stand open and air to whistle through exterior door and lift doors. Describes and illustrates the three common types of relief systems - 1) relief dampers, 2) relief fans, 3 return fans. Discusses application considerations and advantages and drawbacks of each of these systems.