Chiller Plant for Non Engineers: Six Beliefs That Cost Owners Money

Owners do not need to design a chiller plant, but the handful of things they misunderstand about it account for most of the avoidable cooling cost in their buildings.

A chiller makes chilled water, pumps move it to coils, fans blow air across those coils, and heat is rejected outside. Almost all of the avoidable cost in that chain comes from running equipment when it is not needed, running it at the wrong conditions, or never cleaning the surfaces that transfer heat. None of that requires an engineering degree to supervise, only the right questions asked regularly.

How to test a claim like this

Before accepting any claim about your cooling plant, ask what is being measured and over what period. Efficiency quoted at full load says little about a plant that spends most of its life at part load. A proposal that promises a percentage saving without naming the current consumption is not measurable. And any statement about equipment condition that does not reference log data or a test is an opinion. Measurement, period, and method are the three words that keep this conversation honest.

Myth 1: A bigger chiller gives better cooling.

Reality: Oversized plant cycles on and off rather than running steadily, which wastes energy, stresses compressors and controls humidity poorly. Most buildings spend the overwhelming majority of their hours well below peak load, so part load performance and the ability to stage capacity matter far more than the maximum rating. Oversizing is usually inherited from conservative design assumptions that nobody revisited.

How to check it yourself: Compare logged running load against the installed capacity over a full cooling season.

Myth 2: Air cooled and water cooled are interchangeable choices.

Reality: Water cooled plant with cooling towers is generally more efficient but needs water treatment, tower maintenance, space and competent operation, including management of the health risks associated with untreated tower water. Air cooled plant is simpler, uses no water and performs worse as ambient temperature rises, which is exactly when the building needs it most. The right answer depends on water availability, operating competence and the load profile.

How to check it yourself: Ask for part load efficiency at realistic ambient conditions, not a single rating at design conditions.

Myth 3: If the building is cool, the plant must be working properly.

Reality: A plant can deliver comfortable conditions while running two chillers where one would do, with pumps at full speed, valves passing, and a control sequence that was abandoned years ago. Comfort is an outcome the plant can reach inefficiently. Energy per unit of cooling delivered is the measure, and it requires metering of both electricity and thermal output to see.

How to check it yourself: Install or verify thermal metering and track energy consumed per unit of cooling produced.

Myth 4: Cleaning condensers and coils is routine housekeeping of minor value.

Reality: Heat transfer surfaces are where the entire machine does its work. Dust on an air cooled condenser in this climate, or fouling inside a water cooled condenser, directly raises the pressure the compressor must work against and increases consumption measurably. It is among the cheapest interventions available and among the first to be dropped when a maintenance budget is squeezed.

How to check it yourself: Record approach temperatures before and after cleaning to quantify the improvement.

Myth 5: Control settings were commissioned once and need no attention.

Reality: Setpoints drift, schedules are overridden during a complaint and never restored, sensors fall out of calibration, and sequences are bypassed by technicians solving an immediate problem. A plant three years after handover frequently runs on manual overrides nobody has documented. Reviewing and restoring the control strategy is routinely the cheapest saving available in a commercial building.

How to check it yourself: Produce a list of every current override and manual setting, with the reason and date for each.

Myth 6: Replacing the chiller is the way to reduce cooling cost.

Reality: New equipment helps, but if the distribution system, control strategy and maintenance regime stay as they are, much of the expected saving disappears. Pumps running at constant speed, valves that pass, poor temperature differences and overridden schedules will degrade the performance of any machine. Fix the system around the plant before or alongside replacing the plant itself.

How to check it yourself: Audit pumps, valves, temperature differences and control sequences before approving replacement.

What this changes in your decision

• Meter both the electricity into the plant and the cooling it delivers, so efficiency can be observed rather than assumed.
• Require a monthly log of running hours, staging and any manual overrides in place.
• Protect condenser and coil cleaning in the maintenance budget as a measurable, not a discretionary, item.
• Review the control strategy annually against how the building is actually occupied.
• Before approving plant replacement, commission an assessment of distribution, controls and maintenance.

Domira works on buildings that already exist: surveying what is installed, specifying the systems that have to be replaced, and running maintenance and refurbishment work around the people using the property. Tell Domira which asset you are responsible for and we will say what we would inspect first.