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Chiller plants and cooling towers, explained with sources

Written for chief engineers, facility directors and the people who fund their projects. Every figure links to where it came from.

Featured guide · with data figures

Condenser approach, tower approach and fouling: reading them from BMS data

How approach temperatures reveal fouled condenser tubes and cooling towers losing capacity, with results from LBNL's public chiller-plant fault data.

Updated · 3 sources · 3 min read

Data figure

Tower fan speed · every 15 minutes

Tower 1 fouled · UA × 0.65≥95% speed: 85.9% of running intervals
Sample data: LBNL's public simulated chiller plant. About the data Tower 1 fan speed, July 2018. One row per day, one cell per 15-minute interval.

Chillers and the plant

  1. Chiller vs cooling tower: what each does and why they have to be run together

    A chiller makes cold water with electricity; a cooling tower throws the heat away with water. How the two loops connect, what each costs to run, and why optimizing one alone leaves savings behind.

    Updated · 3 sources · 3 min read

    Data figure

  2. Condenser approach, tower approach and fouling: reading them from BMS data

    How approach temperatures reveal fouled condenser tubes and cooling towers losing capacity, with results from LBNL's public chiller-plant fault data.

    Updated · 3 sources · 3 min read

    Data figure

Cooling towers and water

  1. Cycles of concentration: the number that sets a cooling tower's water bill

    What cycles of concentration means, how to measure it, how much water raising it saves, and what limits how high you can go.

    Updated · 3 sources · 3 min read

Measurement and verification

  1. Measurement and verification for chiller plants: what a monthly savings report should prove

    How IPMVP Option B and ASHRAE Guideline 14 apply to a chiller plant, what a credible baseline needs, and what belongs in a monthly verified savings report.

    Updated · 3 sources · 3 min read

NYC compliance

  1. NYC cooling tower rules in 2026: monthly Legionella testing under Local Law 159

    What Local Law 159 of 2025 and the amended 24 RCNY Chapter 8 require of NYC cooling tower owners: monthly ELAP culture tests, 24-hour reporting, annual plan certification and records.

    Updated · 4 sources · 3 min read

  2. Local Law 97 and chiller plants: where chiller efficiency fits in NYC compliance

    What the first year of LL97 reporting showed, what the 2030 limits and the REC rule mean for electric chillers, and where plant efficiency moves the numbers.

    Updated · 3 sources · 2 min read