Some years ago, Sempa was asked to review the energy data operation of a building before the installation of a Hybrid Heating System. The review was completed, and the report was being prepared for presentation to the customer. The building was different than most buildings that had been studied in that area, so the general results were compared with results measured for hotels that had been done.

To the surprise of everyone, the energy intensity was a lot higher than any hotel that had been studied. Unlike the hotels in the area, this building had few outside windows, was largely underground, and had no outdoor swimming pool or spa. The lighting systems had recently been upgraded and were state of the art new systems that would consume less energy than the old lights had done. A review of historical data showed that the energy use had been consistent since the building had been built more than 20 years beforehand. The savings that were the result of the lighting retrofit were apparent, and were in line with the predictions of the contractor that had done the work… Something was wrong – but what…

A computer model of the building was reviewed and the problem was apparent. Gas use was within about 5% of the model prediction, but electricity was almost exactly double what was expected. I was all but convinced that the utility had put the wrong CT or PT rations in the metering system – but a check showed that the metering was in fact correct.
At the time, the maintenance man was an individual that was known for getting himself into details – and sometimes into trouble… We spent time with him and none of us could come up with any explanation.
About a week later, the maintenance manager called – and suggested that we come for a visit…. He had found something. He pointed to the pipes that came from the large chillers, feeding each of the air handlers. Each pipe had a large arrow on it, showing the direction of flow. A temporary temperature sensor had been attached to each air handler, showing the temperature of the chilled water as it entered and left the air handler. Apparently, the water was getting colder, not warmer, as it passed through the air handler …

After a little looking, the problem was apparent. The piping had been labelled backward. The chillers were connected opposite to what was shown on the piping and the air handlers were all connected to assume that the piping arrows were correct. Each air handler had a small pump of its own that was in essence trying to reverse the flow driven by the main chiller pumps. This piping had been done this way when the building was built some 24 years before, and had never been found.. It was only a fluke on Sempa’s part, combined with the diligence and work of a very clever building maintenance manager that found and corrected the problem. Savings achieved after correcting the problem were large.

The real story is the fact that the problem had gone undetected since construction. The building had been commissioned, and had been subjected to a number of audits in the 24 years since construction. No one found the issue, because no one was looking for something so outrageous. It was only when Sempa decided to compare the results with local hotels that it was found. Had the building been another hotel, it would probably have gone unnoticed.
There is a real value to benchmaking buildings and looking at the overall consumption per square meter, and then comparing it with other similar buildings. There should be a pattern, or a reason for any large difference.
This experience taught us a good lesson – one that will not be missed in future…