The standard reference for service life of building components such as HVAC systems, Plumbing, air handlers, Digital Controls, and elevators, etc. may come from many different reference books whose authors have deduced, observed, or tested a sample of similar components to produce a “mean” service life. It is unlikely that any single author has lived long enough to test each sample in service, so some assumptions need to be made when arriving at these estimates.   Read the article……………