AutomatedBuildings.com Article - Automated Continuous Commissioning

Persistent monitoring and diagnostics of system operations directly impacts sustainable energy efficiency in commercial buildings. Examples include everything from detecting heating and air conditioning programming errors to identifying out-of-adjustment settings on control systems, improperly balanced parallel chillers that cause unwanted surges, high head pressure on rooftop unit compressors, oscillating controls that cause unnecessary heating and cooling run times, and incorrect refrigerant charge.

Despite the aforementioned observations, “energy efficiency” usually is associated with improving power consumption ratings for building systems such as lighting and HVAC. In reality, even the most modern, smart buildings—equipped with state-of-the-art electrical and mechanical infrastructure—can and will perform at lower efficiency levels than older facilities if systems are not monitored and tuned for proper operational tolerances.

A case in point: during a recent visit to a local eco-friendly materials store, it was clear that the owners had replaced incandescent light bulbs with fluorescent ones. This particular company received virtually no foot traffic but every light in their showroom was on, and no one was around. Following a suggestion that the benefit of the upgrade in efficiency was being diluted by the lack of lighting control, they decided to install an occupancy sensor to control the lights. On a subsequent visit, the lights in the showroom were again on while no one was there.

It turned out that someone had played with the sensitivity controls and the lights again stayed constantly.

As obvious as this example may be, it points out the simple paradigm that without continuously managing the operation of an energy efficient device, the benefits of the energy improvements will be reduced or eliminated altogether. So how does one best maintain energy efficiency with the added benefits of preventative maintenance?

To sustain peak operational efficiency, a clear understanding of how the equipment operates is critical. Establishing, monitoring and managing the lifecycle of mechanical equipment requires a comprehensive understanding of the equipment’s operating parameters. By collecting appropriate data from the actual operations environment, true operating efficiency levels can be established vs. those provided by the manufacturer, through those created in a building simulation model or through a simple one-time measurement. This understanding provides a foundation for securing the best return on the customer’s energy efficiency investment.

This process of collecting and mining data is at the heart of Automated Continuous Commissioning (ACC). ACC uses access to the existing Building Automation System (BAS) and data from traceable external sources (such NOAA weather data) for this new class of analysis. The data is then used to create performance models of each piece of equipment to track actual (vs. design) operation. New modeling techniques have emerged to create models that persistently predict actual performance within a two percent margin of error. By leveraging these models, building operators and facility managers have a powerful means to diagnose and control component and system faults and anomalies.

The level of granularity provided by an ACC system can identify anomalies that can be generally categorized into three basic groups: control, maintenance, and system performance degradation.

Control issues manifest themselves in some surprising forms. Sensor failures, incorrect schedules and the improper placement of sensors are easily identified and corrected. Other issues are much more challenging to find without continuous commissioning. Consider the example of a site with a domestic water pump on the same schedule as the chiller. To save energy, the pump was put on its own separate schedule since the chiller came on several hours before the site was occupied. This inadvertently broke the schedule for the chiller which caused it to run 24/7. With a simple change in scheduling, a potentially catastrophic maintenance matter can easily be eliminated while energy optimization is restored.

[an error occurred while processing this directive] ACC can detect more insidious issues with sensors that don’t “fail” per se but fail to deliver the correct information to the BAS by drifting across acceptable operating ranges over time. For example, ACC has identified and confirmed, through sensor replacement, highly concentrated failures in aftermarket temperature sensors at specific points in their lifecycle. Without continuous monitoring and a sufficient understanding of how a system is designed to operate vs. how it actually performs, this crucial information is otherwise unavailable.

The benefits of identifying operational anomalies early on through ACC can be found in unexpected places. Take the recent case of an organization with a 150-ton Roof Top Unit (RTU) that was operating at an excessively high head pressure level relative to the particular environmental and load conditions. By deploying an ACC approach, it was confirmed that this was in fact an imminent system failure requiring immediate attention. The company immediately contacted its mechanical service provider and was told that due to exceptionally high temperatures in the region, it would be a few days before service would be dispatched. Unfortunately for the service provider, the compressor failed—a cost of over $11,000—while the customer had to endure two days of discomfort.

Control system missteps sometimes can lead to unidentified and potentially catastrophic system failures. For example, a company recently deployed ACC to monitor the performance of three parallel 450-ton centrifugal chillers. Due to an apparent failure in a control strategy, one of the chillers was allowed to unload and run at a very low part load. By doing so the chiller started surging which would, if unchecked, have led to a potential bearing failure and tens of thousands of dollars in repair costs. The ACC system also identified that these same chillers were being staged improperly for the various building loads. With a few mouse clicks by the BAS technician, the issues were resolved immediately and the high performance system was restored to full operation. Without ACC, this problem would not have surfaced until the next commissioning.

These examples illustrate the clear overlap of operations and energy efficiency. For the first time, ACC allows facilities management the ability to be proactive rather than reactive to HVAC, lighting, refrigeration and environmental system faults, anomalies and failures. As a result, facility executives finally can make proactive and preemptive decisions to materially impact their bottom line from a sustainable energy efficiency and operational optimization standpoint. In addition, understaffed technical teams can better ensure maximum system uptime across facilities.

Mr. Wolins has dedicated his career to the advancement of the energy efficiency industry and has worked over a 25 year period with facilities, their processes and their HVAC, refrigeration, controls and metering systems. He was responsible for the design and execution of many cutting edge energy improvement projects including PG&E’s ACT² and BPA’s small commercial demand response program. Prior to founding SCI, he was a founder of EnFlex Corp. in 1993, which was acquired by Sun Edison in 2008. Mr. Wolins holds a B.S. in Mechanical Engineering from the University of California at Berkeley.

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