May 2012

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Failed Building Automation Systems

Unexpected and Unknown Results

Paul Ehrlich, Ira Goldschmidt & Angela Lewis
Building Intelligence Group

As published
Engineered Systems 
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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:

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:

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 IraPaul 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  We also invite you to contact us directly at or


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