An energy consultant said replace the chiller. The panel data said clean it.

What this case study covers

A commercial office tower was about to replace a 500-ton centrifugal chiller on an energy consultant’s recommendation. A structured diagnostic using only data the chiller already reports proved the problem was waterside biofilm at roughly eight times the rated condenser fouling allowance, caused by a pump VFD retrofit that dropped tube velocity below the OEM minimum. The machine was cleaned, the cause corrected, and the replacement cancelled.

Inside this case study

• Why a chiller can’t be inspected, and what it reports instead
• The heat-balance gate that proves the data before any diagnosis
• How approach and waterside ΔP separated film fouling from restriction
• The fouling-factor math: U from 312 to 190, about 8× the AHRI allowance
• The latent root cause: a pump energy retrofit nobody reviewed
• Corrective action and verification: approach back to 1.9 °F in 45 days