Problems are inevitable if long-term changes to the chilled-water system performance are not accounted for in the initial design of chillers, pumps, and cooling coils, according to an article on the Consulting-Specifying Engineer website.

To evaluate the best design for long-term operation it's first necessary to understand what happens to the performance of chilled-water cooling coils as a system ages. Issues can include fouling and increased airflow.

As water and air flow through and around the coil, particulates and scale accumulate on the airside and waterside surfaces of the coil, a phenomenon known as fouling. 

Also, renovations can result in additional airflow requirements due to newer codes, increased heat loads, or additional square footage. While increasing the fan speed may satisfy the needs of the renovation, it does negatively affect the chilled-water coil performance.

Read the article.