Failed Building Automation Systems Unexpected and Unknown Results

Paul Ehrlich, Ira Goldschmidt & Angela Lewis Building Intelligence Group As published   May Issue - Column

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We expect controls and building automation systems (BAS) to operate buildings in an efficient manner, keeping the occupants’ safe, comfortable, and doing so using as little energy as possible.  But often these systems do not work properly.  They fail due to a number of problems including errors in design, installation, and construction.  But most often the problems are due to changes introduced in operation, often as a result of changes to building use, failed components, or system upgrades. 

While it is not remarkable that these systems fail, what is surprising is that many failures go without being noticed.  How is this possible?  The short answer is that as long as the building remains somewhat comfortable, the systems are assumed to be working.  When a problem impacts comfort, for example a control valve that doesn’t open allowing a unit to cool, then the system operator will typically look for the problem and get it resolved.  But when the problem does not directly impact comfort they become both unexpected and unknown.  This leads us to the old saying about these systems “They don’t work but they aren’t broken.”

The range of system failures is broad, ranging from setpoints, which are not optimum to sever problems.  Here are a few common areas were we see problems:

• Economizer Controls:  We see a lot of problems with the control of economizers on everything from packaged rooftop units to large central systems.  The problems range from incorrect setpoints, to bad sensors, to lack of proper setup.  The use of economizer is fairly straightforward but improper setup is common and hard to detect.
• Simultaneous Heat and Cool:  The use of reheat on VAV systems is critical during cold weather, to de-humidify and to deal with zones that have high ventilation loads but low occupancy.  However the use of reheat often covers up much larger system problems.  For example we recently evaluated a building were the fans operated continuously, sub-cooling the entire building and forcing reheat to run all night.  Since the building stayed comfortable the efficiency problems were readily masked.
• Extended Hours of Operation:  It is not unusual for the operating hours of building systems to be much greater then occupancy hours.  In fact many buildings end up running systems 24x7.  Frankly leaving things on at all times is seen as the easiest way to deal with occupant complaints and comfort problems.  Of course doing this results in excess energy for heating, cooling, as well as ventilation.
  

While resolving many of these problems is not complicated, finding them can be.  There are a series of tools that we use to find and analyze control system problems.  These include:

• Site audits including interviews and equipment inspections.
• Analysis of BAS systems including screens, alarms and trends (if available).
• Extensive data logging using either the BAS or standalone data loggers.
• Evaluation of building level smart meters (when available).
  

The most important of these tools are the trends, data logs, and smart meter information, which occur over an extended period of time.  This allows us to see what is happening at night and on weekends and also how systems react as the outdoor air conditions vary. 

Ideally we would like to see HVAC equipment controls and BAS systems become self-monitoring and correcting.  There has been quite a bit of work done in this are and “continuous commissioning” tools and services are now available in the market.  But ideally buildings should be like your car.  The systems should operate properly, and when there is a failure the operator should be clearly notified.  Until this is available in buildings then there will be a need for engineers to act as detectives looking for the unexpected and unknown.

About the Authors

Paul and Ira first worked together on a series of ASHRAE projects including the BACnet committee and Guideline 13 – Specifying DDC Controls. The formation of Building Intelligence Group provided them the ability to work together professionally providing assistance to owners with the planning, design and development of Intelligent Building Systems. Building Intelligence Group provides services for clients worldwide including leading Universities, Corporations, and Developers. More information can be found at www.buildingintelligencegroup.com  We also invite you to contact us directly at Paul@buildingintelligencegroup.com or ira@buildingintelligencegroup.com

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