How can I troubleshoot a water chiller that is not cooling properly?

Good question, and it is usually diagnosable with a methodical walk-through. 'Running but not reaching setpoint' almost always comes down to one of four things: not enough refrigerant, poor heat rejection at the condenser, poor water flow through the evaporator, or the compressor/controls not doing their job. Narrow it down cheapest-and-safest first:

1. Confirm it is real (sensor + setpoint). Measure the actual leaving-water temperature with an independent thermometer and compare it to what the controller shows and to the setpoint. A drifted sensor or a wrong setpoint makes a healthy chiller look like it is underperforming, or makes it stop early thinking it is satisfied.

2. Chilled-water flow (common, often missed). A chiller cannot move heat it never receives. Check the chilled-water pump runs, the Y-strainer is not clogged, all isolation valves are open, and the loop is vented (an air-bound coil kills flow). Compare return vs supply temperature across the evaporator: a very small split with poor cooling usually means low flow or low load.

3. Heat rejection at the condenser. Air-cooled: clean the condenser coil (dust is brutal here), confirm every condenser fan actually spins, and make sure hot air is not recirculating around a boxed-in unit. Water-cooled: check the cooling tower fan and fill, the condenser-water pump, tower level, and condenser-water temperature. Scaled condenser tubes raise head pressure and cut capacity.

4. Load and cycling. Has the load changed (more units, a hotter space)? Is it short-cycling or alarming? Note any fault code on the controller exactly as shown, it usually points straight at the subsystem (flow, high-pressure, low-pressure, freeze, phase-loss).

Stop and call a technician for anything involving refrigerant gauges, charge, a suspected leak, superheat/subcooling, the expansion valve or compressor internals. Low refrigerant cannot be confirmed by eye, and topping up a leaking system without fixing the leak just wastes gas and harms the compressor.

If you can say whether it is air-cooled or water-cooled, roughly how far off setpoint it is, whether there is any ice on the pipework, and any code on the display, we can point you at the most likely cause.