Before replacing existing furnace equipment, it is necessary to complete some tests and calculations as well as visually inspect the current system arrangement in order to accurately size the new furnace and consider changes in configuration, if needed. Furthermore, this pre-investigation may determine whether additional work beyond the localized furnace installation is needed (ductwork improvements, asbestos abatement). While there are several important action items that should be completed before installing the new furnace, three key items are discussed in the next pages.