Problem Solving: Gather All the Evidence Before You Diagnose the Problem

Solving problems is what we do at MSC, and this means our technicians must often think like a detective. This requires listening to eyewitness accounts and asking the right questions, following clues, avoiding premature conclusions, and, most importantly, gathering hard evidence. Hunches, gut feelings, and preconceived notions only get you so far.

The controls contractor on a large retro-commissioning project was stymied by an inability to successfully trend discharge air and space temperatures. First, they blamed issues on chilled water temperature problems, then moved on to blaming plugged strainers, airflow issues, low GPM flow, bad coil design, etc., but couldn’t present any proof. Owners and project managers were rapidly losing confidence in the retro-commissioning agent and called in MSC to trace the problems to the source.

MSC service technicians took ultrasonic flow measurements on two AHUs to determine GPM and traversed the discharge duct work to determine CFM. A full temperature profile was performed on the cooling coils to measure exact temperature and thermal video was taken of the chilled water coils and surrounding area. When all was said and done, the data clearly showed that water flow, airflow, and temperature were all performing to design intent, disproving the controls contractor’s various unsupported assumptions.

Based on the gathered data, MSC turned to the instruments and found that almost all of the discharge air and space temperature transmitters were out of calibration anywhere from 2.4°F to 11°F. Ironically, it turned out that the finger-pointing contractor had recalibrated all of the temperature sensors incorrectly as part of their own retro-commissioning process, and none of the problems they pointed out ever existed.