Comparing economizer relief systems

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 economizer is a system to relieve the excess outdoor air supplied to the building when the economizer is enabled. Without an adequate relief system, the building can become over-pressurized, causing exterior doors to stand open (a potential security issue) and air to whistle through exterior doors and elevator doors. For very tight buildings, the pressure buildup can reduce supply air rates, Maximum building pressure to avoid these problems is typically about 0.05 in. w.g. to 0.10 in. w.g. (12 Pa to 25 Pa).