As Seen On: issuu.com November 2020
The healthcare industry wrestles with the long-running problem of patient non-adherence. The consequences are waste of medication, disease progression, reduced functional abilities, lower quality of life and increased use of medical resources, such as nursing homes, hospital visits and admissions.
The built environment grapples with its own version of non-adherence. Buildings of all types and sizes, including healthcare facilities, are designed, constructed and commissioned with mechanical systems to regulate the indoor environment, in particular temperature and humidity. The challenge facility managers face is HVAC systems experience what is referred to as ‘performance drift.’
On the day a hospital is commissioned and perhaps for the first few months afterward, the cooling system operates flawlessly. Over time, though, component efficiency, operating settings and system conditions drift away from the originally installed and commissioned system. Not surprisingly, efficiency and system performance degrade incrementally. The consequences of this version of ‘non-adherence’ are reduced occupant comfort, unnecessary use of energy, related costs and carbon emissions.
HVAC systems that don’t work as intended result in the unnecessary consumption of energy. Without automated maintenance alerts and regular recommissioning, most buildings will experience performance drift of 10 to 30 per cent in just two years.
Reversing and preventing that loss in efficiency is important and not just for the cost savings. Research shows commercial buildings are responsible for nearly 50 per cent of electrical energy-related greenhouse gas emissions.
Buildings are operating below their optimal efficiency because many operators don’t get the data that’s necessary to understand the HVAC system or if received, they lack the tools to discern it.
Most performance drift can be attributed to changes that take place within the mechanical system: filters become clogged; sensors become fouled or simply lose calibration; valves are adjusted and never returned to their settings; and digital control settings are changed and not properly reset. In some instances, digital controls intended to monitor and modulate equipment operation are turned off or even disconnected entirely.
A smaller portion of performance problems can be related to the operating environment. Buildings often go through retrofits for new lighting, windows or shading. Occupancy numbers can change along with tenant makeup, particularly in commercial environments as businesses evolve and shift locations.
Fortunately, there are technologies and methods to detect and reverse performance drift in mechanical systems.
THE HUMAN COMPARISON
HVAC systems are similar to the human body, with a large percentage being hydronic. This means they rely on fluid to add or reject heat from the indoor environment. In the same way that a strong heart and good circulation of blood are key measures of human health, the flow rates in an
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| An integrated plant controller, new chiller and cooling tower converted Methodist Dallas Medical Center's cooling system to an all variable speed format. |
HVAC system are an important indicator of how well that system is functioning.
In a standard annual checkup, pulse and blood pressure are key data points collected. Just those few measures are a strong indicator of overall health, especially when viewed in comparison to values recorded in previous annual checkups. Like the human body, the flow rates in an HVAC system indicate how well it is operating and where any problems lie.
Without information on system flow, it is difficult to diagnose and optimize performance. With it, the picture changes entirely. In any chilled water system, knowledge of the cooling load is the starting point. The cooling load is equal to flow multiplied by system delta T. In non-technical terms, load is the amount of cooling required to reach or maintain acceptable indoor temperatures. Traditionally, buildings have been designed to function only by observing whether temperature setpoints in the system are being maintained; the HVAC system operates if a threshold temperature is reached.
Flow meters are rarely installed in these systems and almost never on the associated cooling tower loops. As a result, system performance drift is common. In the secondary circuit, changes in flow rate that can’t be explained by demand may indicate clogging, leakage, changes in settings or valve malfunction.
In a cooling tower or condenser circuit where water circulates between a chiller and cooling tower, the efficiency of the heat rejection is rarely known or even tracked. Understanding flow and changes in flow rates is a key first step in building a true load profile of the chiller and the heat rejection process equipment, whether open or closed circuit. The flow data alone can be used to diagnose a clog or decreased cooling tower function. With the addition of readily available temperature data, the process of optimizing the entire cooling system can begin.
Flow data provides new abilities for diagnostics and clues for new optimization approaches. It gives more data for performance commitments and condition-based maintenance.
Using flow data from both sides of heat transfer devices also enables heat balance calculations to assess the performance of those heat transfer or mechanical cooling devices long before they become problematic for maintaining setpoints.
ACTIVE PERFORMANCE MANAGEMENT
Another industry innovation is to think of the intelligent pump as an accurate flow meter. New design envelope pumps provide flow data accuracy within five per cent of a reading, as well as a host of higher level solutions that leverage accurate flow data to optimize system performance and detect degradation. These are known as active performance management solutions.
Active performance management takes a systems management approach that will optimize a HVAC system at any stage of a building’s life cycle, drawing on analytics from flow information and heat balance models of the system. Accessing and learning from a broad network of installations and responding to changing HVAC requirements, the technology includes machine learning that is enabled through the system flow of information.
Active performance management is available to customers as a set of services and solutions, but the underlying technologies are built into every design envelope product and enabled with a subscription-based service. This service provides asset management tools, system diagnostics, performance reports and continuous upgrades learned through the combined operating experience of many installations. All this is made available through mobile performance dashboards and remote connectivity that continuously validate system savings.
Even with the sophistication of modern building automation systems and the data they provide, many building operators are still left trying to optimize HVAC systems using a trial and error approach. Active performance management ensures longterm efficiency of a mechanical system through informed, data-driven responses to changes in load and system performance.
The important point for facility managers and healthcare administrators is to understand that performance drift in buildings and mechanical systems isn’t a condition that has to be accepted. Better options exist in the form of advanced mechanical solutions and services to optimize performance. Although the changes involve an investment, payback is usually within three to five years.
