R-Pro › Field cases › Components

Cooling Tower Outlet Water Temp 3°C Above Design — Approach Deterioration

Likely causes

Fill covered with scale or biofilm — heat transfer area reduced

Check: With fan and pump off, inspect fill — white scale or green slimy biofilm. Test water (pH, conductivity, TDS); pH >8.5 or conductivity >1,500 μS/cm promotes scale. Also check fill for physical damage/warping

What to do: 1) Water treatment: add scale inhibitor and biocide; enable automatic conductivity-based blowdown (maintain 1,000–1,500 μS/cm). 2) Fill cleaning: pressure wash top-down at 10–20 bar; for heavy biofouling, circulate 50–100 ppm sodium hypochlorite for 4 hrs then drain and rinse. 3) Replace damaged fill (PVC film fill typical life 5–10 years)

Air short circuit — humid exhaust air recirculating to inlet

Check: Measure wet-bulb temp at air inlet vs outlet — inlet >2°C above ambient = recirculation. Check for surrounding buildings/obstructions blocking airflow, adjacent towers or exhaust fans on the same roof, and whether discharge hits walls or barriers in the prevailing wind direction

What to do: Remove obstructions at air discharge, relocate adjacent exhaust fans or extend ducting. If a recirculating wall is nearby, install wind deflector to redirect flow; when adding towers, keep at least 2D spacing (D = tower diameter). For multiple roof-top towers, stagger discharge directions

Reduced fan airflow — belt slip, blade pitch drift, or gearbox issue

Check: Measure fan motor current (below 70% of rated = airflow shortfall), RPM (within ±5% of nameplate), belt deflection (10–15mm normal; more = slipping). Measure blade pitch with angle finder (±0.5° of design), check gearbox oil level and metal particles. Measure average discharge velocity at the top with anemometer

What to do: Retension or replace belt (replace if slip marks remain). Reset blade pitch (use level and angle finder; all blades identical angle). Change gearbox oil; if metal particles present, inspect and replace bearings/gears. If motor is burnt, replace with same kW

Cooling water flow out of design (too high or too low)

Check: Check flow meter — within ±10% of design LPS. Too high = insufficient dwell time and weak cooling; too low = filter/pump issue. Also check pump discharge pressure/current and Y-strainer differential

What to do: Adjust control valve (butterfly/ball) to within ±10% of design; use VFD to trim pump speed if needed. Adjust header bypass. If flow low, clean Y-strainer first. Consider automatic flow control based on load (conductivity/temperature)

Heat load exceeds tower capacity — system expanded without upgrading tower

Check: Calculate current heat load: Q(kW) = flow(L/s) × ΔT(°C) × 4.186. Compare with tower rated capacity. If load exceeds 100% of rating, capacity is insufficient. Check if process equipment was added after install

What to do: Short-term: try lowering setpoint and increasing blowdown to drop outlet temp. Medium-term: add parallel tower (same size/flow). Long-term: full replacement (larger or hybrid type). Start from the design heat-load calculation and drawings

Field tip

Approach (outlet water temp − inlet wet-bulb temp) normal range 3–5°C. On-site, measure inlet wet-bulb with a portable thermometer and judge immediately. Large approach means the tower is underperforming even if water temp looks OK — in hot summer, water temp may look fine but large approach still needs service.

All 565 cases work offline in R-Pro, with error codes for 62 brands and P-T data for 108 refrigerants.

Open R-Pro →

Related cases