How to select an air handling unit

Air handling units come in all shapes and sizes. Learn to balance and prioritize all of the choices related to performance, efficiency, maintainability, and space constraints.

Learning Objectives

1. Know the different types of ahu coils, and their basic anatomy

2. Understand the codes and standards that govern AHU specification

3. Learn about how energy can be saved in HVAC systems that use AHUs.

A basic definition of an air handling unit (AHU) might be “a box with a fan, coils, and filters.” From there it gets considerably more complicated. Proper selection of an air handler requires answering myriad questions ranging from “what capabilities are required?” to “will it fit?” Only after establishing these basic project constraints can the art of evaluating and selecting an AHU begin.

Before starting this process, it’s important to realize that there will not be a “perfect” selection for any AHU as many competing criteria, not the least being cost, will force compromises. It is the engineer’s job to balance and prioritize all of the decisions related to performance, efficiency, maintainability, and space constraints to select a unit that has the lowest lifecycle cost for a given application.

This article provides general information and guidance on the selection of various ahu heat exchanger components, starting with a brief description of the major categories of AHUs. While much of the discussion in the remainder of the article relates primarily to large AHUs, the general considerations can be applied to any size.