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Networked highperformance HVAC

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Energy savings and lighter carbon footprints in commercial buildings are becoming increasingly important to the bottom line of corporations. The software and engineering experts Optimum Energy based in Seattle, USA introduce you to new enterprise application approaches that are transforming the way commercial HVAC systems are operated and maintained.

Energy efficient HVAC is not simple to achieve or sustain. Traditionally, HVAC equipment components are designed to operate efficiently in isolation and building automation systems (BAS) control the equipment by turning it on and off automatically. Operating data that resides in the BAS typically is not easily accessible by building operators. If operating data is available, it’s usually in the form of unformatted streams of data points.

In recent years, by using VFDs, it is possible to vary the speeds of rotating plant equipment (e.g., fans and pumps) and capture the exponential savings that comes from running plant equipment at partial loads. Additionally, innovations in control methods have made it possible to optimize all of the equipment in an HVAC system by networking the equipment together and intelligently matching air temperature requirements with equipment speeds.

Unfortunately, even optimized plants often fail to maintain their promised efficiency over time. This happens because traditional methods of plant operation and maintenance are based on an outmoded static operating model that treats the plant as a series of mechanical equipment rather than a networked, interrelated system.

The Performance Drift

While, commercial HVAC systems generally are well engineered to meet the specific needs of a particular site, their complexity and custom design lends itself to “drift,” or the degradation in performance over time as a result of changes and malfunctions in mechanical and control systems. 4 OptimumMVM Whitepaper custom “software” solutions. As a result, utilities often require some means of measuring and verifying plant efficiency at a point in time. These utility audits are sometimes repeated to determine that a plant is meeting targeted efficiency goals. There is no question that commissioning can provide a good outcome in the short term, with building operating efficiency improvements typically in the range of 5% to 20%. Because commissioning is focused on improving efficiency at a single point in time, however, commissioned plants – even when maintained at the highest standards

To remedy this problem, the HVAC industry has evolved various approaches to optimize HVAC system performance. The most widely recognized approach is the practice of “commissioning,” a process that includes an assessment of the HVAC system, identification and correction of mechanical and control issues and development of new operating procedures. One efficiency strategy is the use of variable speed equipment and custom-developed control methodologies. But, solutions designed uniquely for a specific site are unproven, can take weeks or months to program and require hands-on functional testing to verify the system is working as designed. In addition, without real-time measurement and verification, it is difficult to verify that predicted energy savings are realized or can be sustained over time. Utility audits are sometimes repeated to determine that a plant is meeting targeted efficiency goals. Because commissioning is focused on improving efficiency at a single point in time, even when maintained at the highest standards, commissioned plants are subject to performance drift.

 

The Savings Opportunity

While commissioning has been considered a best practice to date, the availability of enterprise applications that utilize networked software solutions – providing real-time measurement, verification and management of HVAC operating performance, now make it possible for building operators to not only increase the efficiency of their HVAC systems, but also to ensure those savings persist.

Web-based measurement, verification and management service acts as a continuous feedback loop that provides detailed real-time and historical performance data so operators can quickly detect, diagnose and resolve HVAC system faults.

Networked Software Solutions

Today, building owners and operators are reducing commercial HVAC energy consumption by 30% to 60% by deploying networked applications that combine advanced control methodologies and Web-based measurement, verification and management services. The Mineta San José Airport, for example, reduced HVAC energy use by more than 1.25M kWh in 12 months – a 51% reduction in energy use.

To achieve these results, it implemented control software for chilled water plants and variable air volume systems to automatically and continuously optimize the operating efficiency of the entire HVAC system based on real-time building loads. The third step was the introduction of software that made available the real-time HVAC system performance data, that is critical to ensuring energy efficiency and the resulting operating cost reductions. This helped the San Jose Airport to maintain a monthly wire-to-water average range of 0.61 to 0.65 kW/ ton in the first year of operation, a more than 50% reduction in energy use. The plant is still operating at these levels today.

Networked Enterprise Applications

Achieving the goal of persistent performance that is impervious to performance drift over the years, requires continuous measurement, verification and management (MVM) techniques that enable immediate and precise maintenance of the HVAC system. Networked software solutions take the guesswork out of HVAC operations. By displaying plant efficiency graphically, the latest Web-based MVM service puts control into the hands of the building operator, giving them the performance data needed to continuously “commission” the building for optimal energy performance. With the reporting and analysis capabilities of MVM solution, building owners no longer have to rely on physical plant inspections or extensive functional testing to detect and diagnose system faults.

Setting New Standards

While custom engineered efficiency solutions and commissioning can result in energy savings, they are expensive and carry some inherent risk as custom solutions. Just as importantly, these traditional methods do not leverage the data that is available via the BAS to sustain high levels of energy reduction over the long term. The conventional BAS, which primarily is used as a device controller, is also a clearinghouse for valuable HVAC system operating and building load information. Until recently, however, BAS data was largely untapped. Today, by applying networked enterprise applications to commercial HVAC systems, it is possible to more optimally control the HVAC system for maximum energy reductions using standardized software, and fundamentally change the way buildings are managed and maintained.

Case Study:

The Problem: The chilled water pumps and tower fans in the centrifugal chiller plant of a 315,000sqft commercial office building in Northern California appeared to be running, but the operating data coming from the building automation system (BAS) was inconsistent with normal operations.

The Inference: Based on the data, it was believed that the variable frequency drives (VFDs) were not communicating correctly with the BAS.

The Solution: With data in hand, the controls contractor rapidly honed in on the system fault and troubles hooted the communication links between the VFDs and the BAS. It was quickly discovered that an end-offline resistor had been inadvertently removed, which caused the communication failures between the VFDs and the BAS.

Without access to operating data via MVM software, the anomalies would not have been apparent. The chilled water pumps and tower fans likely would have continued to operate under default settings until the system could no longer keep up with building load demands. As a result, the potential energy reductions and cost savings from using optimum HVAC system would not have been achieved.

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