We expect controls and BAS to operate buildings in an efficient manner, keeping the occupants safe, comfortable, and doing so using as little energy as possible. But often, these systems do not work properly. They fail due to a number of problems including errors in design, installation, and construction. But most often, the problems are due to changes introduced in operation, often as a result of changes to building use, failed components, or system upgrades.
While it is not remarkable that these systems fail, what is surprising is that many failures go without being noticed. How is this possible? The short answer is that as long as the building remains somewhat comfortable, the systems are assumed to be working.