Direct injection of water from a cooling tower into a closed chilled water loop has been used to reduce refrigeration chiller operation, save energy and reduce costs. This practice has led to severe corrosion and fouling problems in the HVAC systems of many commercial buildings. The applicable mechanisms are microbiological fouling, microbiologically
infhrenced corrosion (MIC) and suspended solids deposition. This paper discusses the effects of direct “free cooling” condenser water operations on corrosion and microbiological control in condenser and chilled water systems, and describes some case histories of problems that have resulted from free cooling operations. Suggestions are offered for
operating practices to minimize these problems.