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Digging Deep to Cure HVAC Inefficiency

Vista Peak Prepatory LEED Gold
Photo Credit: RTA/MOA

Craig Wright has a problem. He didn’t know exactly what it was, but he knew he had a problem.

Wright, the Natural and Renewable Resources Manager at Aurora Public Schools in Colorado, was spending too much money on heating and cooling at Vista Peak Preparatory, which is a 220,000 square foot high school.

Essentially, the system in the building – which was built to LEED Gold specifications – uses a two-pipe structure to funnel outside air in the system for free cooling. The idea is that the use of free air reduces the amount of cooling the chillers must do and, therefore, the energy used by their fans.

The challenge – and the reason that BuildingIQ eventually was brought into the mix – is that a lot of things can go wrong. “We didn’t really understand the influence that the air handling control strategies had and their sensitivity to proper air flow measurement, proper building pressure as well as CO2 demand control ventilation.”

The result is that a poorly tuned system has the exact opposite impact of what was intended: Fans in the chiller were working overtime. “When one component of, for instance, a large air handler deviates or drifts from its measured values — such as outside air flow or CO2 concentration – it can place undue burden on fans,” Wright said. “That increases fan energy use, which in turn puts undue burden on optimal functioning of the heating and free cooling loop.”

Simply put, a system, from a car to a lawnmower to an HVAC system, wastes money if it is not working optimally. Wright said that the system was sending $75,000 per year into the atmosphere, so to speak.

The BuildingIQ system was installed in 2015 via a pilot program from Xcel Energy, the utility that serves the school. It is being used, Wright said, “as a means to further optimize equipment that ideally was already operating properly. It gives us the ability to take into account future weather and existing building load conditions and optimize equipment to use energy more efficiently in the space.”

The BuildingIQ equipment serves two main roles. In general, it amasses data that enables more precise automation. Suppose, for instance, that the heat in the building is set to turn on at 5 AM so that it is a desired temperature is reached at 6:30. That would be unnecessary, however, during an unseasonably warm week. The BuildingIQ system can seek out that data and make the adjustment automatically.

It also more directly confronts the problem Wright was facing. The system is paired with the building automation system (BAS), which held the answer to the riddle. Before implementation of BuildingIQ, the cause of the problem – why the fans were being overextended – was not apparent because the staff didn’t know what data to access. In essence, the job of determining what questions to ask the BAS switched from the Aurora staff to the BuildingIQ software.

The results were suprising. “We did not know the extent to which so many parameters and control devices either weren’t working or had drifted out of calibration,” Wright said. “It revealed that that there were underlying problems, not a single root cause. That was kind of an eye opening experience for us.”

Wright and his staff have taken corrective action. “We’re calibrating air flow measuring stations, we are addressing our CO2 ventilation strategies and optimizing air temperature to switch between heating and free cooling,” he said.

Though fan use has been curtailed, challenges remain. “We need to do more calibration, repair air flow measurement stations and I would like to implement pre heat and pre cool strategies prior to [daily] occupancy.”

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