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By Maria Lupo and James Franke
Building Automation Article Use Policy
In every modern commercial building, electricity and water are wasted, as building systems are not typically optimized over time. Facility managers often turn to third party software analytics or capital upgrades, like a chiller replacement or lighting retrofits, in their quest to minimize energy expenditure and protect their bottom line.What facility managers don’t always realize is that the answer to optimizing the operations of their building may already exist in their building automation system (BAS). Designed to centralize control and monitoring of the heating, ventilating and air conditioning, lighting, and auxiliary systems, the BAS also holds the key to optimizing the efficiency and operations of every modern commercial building. From low hanging fruit like temperature setbacks and equipment scheduling to often underused calculation, trending, and analytics, there is untapped potential in both the functionality and usability within most BAS. An existing BAS is a system that the organization has already invested in. It is time to maximize that investment.Optimizing BAS functionsThe first point to consider is BAS functionality: the range of operations that can be automatically run on a BAS. There are a range of functions within the BAS that can be optimized to achieve greater comfort and more fluid operations. Often underutilized BAS functionality, like tracking electric metering and domestic water use and implementing adaptive sequencing, typically can be implemented at low-cost.Energy metering. Traditionally, the BAS is employed to aid in the performance of basic sequencing when operating mechanical equipment. One area of functionality often overlooked is the monitoring of electrical systems, including power meters, switchgear, lighting, and variable frequency drives. Using the BAS to gather and intelligently trend electric data at a more granular level will reveal how the building uses energy over the course of a day, week, month, and year-to-year, allowing the facility manager to uncover easy and inexpensive ways to reduce consumption. This recognized benefit has led to the incorporation of electrical energy monitoring for distinct load types in standards such as ASHRAE 90.1-2013. The more information and data available to analyze, the more opportunity to make impactful adjustments to system operation and business cases for integrations with other building systems or implementation of new technologies.Utility companies are putting more emphasis on instantaneous power usage, or demand. Buildings have control over their instantaneous energy usage by changing how mechanical systems operate. Trending electrical demand in the BAS makes it easier to correlate mechanical system operation with demand. For example, in the early morning, when the building is heating up, it may be best to turn the boilers on earlier, or only turn one on, to ride through the energy spike based on the demand trend from the previous day.Monitoring energy usage is also an easy way to diagnose abnormalities and failures. Simply programming algorithms and formulas within the BAS can provide BTU data at any load or generation system, with few if any additional sensors needed, based on temperature readings and flow rates that already exist in either airside or waterside systems. Energy metrics can be calculated, displayed, and used to diagnose issues across building systems, while also revealing the difference in energy values between identical equipment. The latter could reveal an imbalance in one chiller over another, a sticky heating coil valve in one of many identical air handling units, and other issues.Domestic water usage. Domestic water usage can easily be monitored at the BAS. It is almost impossible for buildings that use a lot of domestic water to understand where and how much water is used and where it can be saved without detailed monitoring. For example, if make up water for cooling towers was monitored, it would be possible to identify if a leak is occurring, where there’s overfilling, and where other operational deficiencies are occurring.
Adaptive sequences. Implementing adaptive sequences can be another simple way to optimize mechanical efficiencies. Because the BAS is already monitoring and controlling the mechanical systems, the data required to establish the appropriate adaptive sequences is already present, with no additional devices necessary. A common fix as part of retro-commissioning, adaptive sequencing — including discharge air temperature reset, static pressure reset, and optimal start/stop — has low implementation cost and payback quickly with energy savings.On a day when it’s not hot or sunny and the building load is less, it is possible to raise the discharge air set point and still maintain comfort, saving a considerable amount of energy. Requiring no change of hardware or new controllers, the capability for these temperature and pressure resets almost always exists in the BAS. The issue is that they are often not programmed correctly.Similarly, pre-programming the stop and start of the mechanical equipment reduces equipment run time and takes the decision-making off the facility staff. For buildings where the BAS already controls the air handling units, optimal start/stop requires no additional hardware or sensors. Another relatively simple sequence enhancement in the BAS compares the outdoor air temperature and the space temperature, turning the mechanical systems on at the right time to make the space comfortable, without starting them too early. This can result in significant energy savings throughout the year, and reduces the facility staff’s time and effort.
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