old four story brick factory building had no air-conditioning except for a small office area with a few window air conditioners. Factory work in the building could get quite hot especially during the summer. Many of the factory's big reactors gave off considerable heat and cooling was necessary. The factory used chilled brine water to cool the reactors. Salt water would be circulated through a chiller, a big electric powered refrigeration unit on the roof and then piped to the reactor.
One July the chiller was requiring more electricity to keep up with demand. The load was similar to the prior year and the equipment checked out fine. But the problem was escalating, with the brine temperature now about five degrees higher than the set point.
What was causing the chiller to require more electricity and why was it not able to keep up with the demand?
Here's the rest of the story.
The engineer assigned to the problem recognized that the heat load went up at night. This was counter-intuitive.
Demand should be higher during daytime when the sun added heat to the building. Readings on the electric meters of the chiller system showed demand spiked sometime after 6:00 PM. The higher demand continued until early morning when it would slowly drop off to a more normal level.
There was no doubt that something was using chiller capacity in the evening hours.
The investigative engineer started wandering around the factory. As he wandered the factory seemed to be getting colder. There was the feel of cool blowing air.
Finally, he came to a bank of several large truck radiators connected the brine lines. Several fans were blowing through the radiators cooling the factory. Late shift workers rigged an impromptu air conditioning system. This was putting a heavy load on the chiller. Each floor had a similar air conditioning system.
The late-shift workers theorized they could get away with their home-made system as most of the supervisors worked during the day shift. At 6:00 PM they would drag out the radiators, connect up the lines, turn on the brine, and run the big fans.
It was left to the plant manager to explain why the air conditioning had to go. The reactors running too hot, and the electric bill was going through the roof. In this case, the detective work was really more about foot work. Track down the source of the problem, and you should find the cause. The engineer simply followed his nose until it was cool.