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Screen shot from Arlington's FDD software

Screen shot from Arlington’s FDD software

While thumbing through a trade magazine in the summer of 2014, I noticed an article about Microsoft. Its Director of Energy and Building Technology, Darrell Smith, was using software to understand the inner workings of their HVAC systems. Microsoft had 55 million sq ft of buildings, Arlington had 1.3 million; but that didn’t deter me. I wanted to do what Microsoft was doing. I wanted to understand, day or night, on site or off, if my machines were operating efficiently. While not at the same scale as the software giant, Arlington is utilizing the same fault detection and diagnostics software program, to analyze operations and upgrade HVAC efficiency.

Fault detection and diagnostics (FDD) is software that combines multiple points of data for each piece of equipment and compares the existing operation of that piece of equipment to a pre-determined efficient sequence of operations. If the FDD finds that the piece of equipment is not running efficiently, it generates a fault and the fault data is shown on the FDD screen, including a diagnosis of the probable cause of the fault.

FDD allows for trending of a piece of equipment over a long period of time including all of the multiple data points associated with the equipment; for example: occupied/unoccupied mode, discharge air temperature, room temperature, outside air temperature, actual supply flow, damper position etc. Via FDD, we can literally see the operations of our HVAC equipment.

Generic air handling unit

Generic air handling unit

The data available from the FDD is user friendly and simple to understand. Fault names can be changed to be compatible with terminology used in Arlington. AHU 1 and RTU 1 become music room and third grade classroom. Data is available in graphic format; blue for cold rooms, red for warm rooms. The FDD software can be incorporated with a work order program so that a fault generates a work order. That way, all communication regarding the fault and work order can be memorialized within the software program. The goal for Arlington is to begin the incorporation of the FDD with our work order program to create a more systematic and reliable process.

The information from the FDD software allows Arlington to gather information about a problem before calling in a third party contractor to solve the problem. With the information from the FDD, we are able to pinpoint which pieces of equipment are malfunctioning. In-house maintenance staff is able to research issues in a school building while school is in session, even if they cannot access the room until school is dismissed for the day. FDD adds value to staff efficiency and deployment.

Generally, retrocommissioning – a systematic process for identifying and implementing operational and maintenance improvements – is assumed to save 15% of the total energy consumption. This has helped the town achieve its 20 percent energy reduction goal as a DOER designated Green Community. FDD is one step above retrocommissioning as it is akin to constant commissioning. We believe that FDD is the next step in “deep dive” energy efficient operations.

Now if only there were personal FDDs.

Written By:


Regional Energy Manager

Ruthy Bennett is the Regional Energy Manager for the Towns of Arlington and Bedford and is a licensed architect and LEED Accredited Professional. She has a background in housing development and has been focusing on the "triple bottom line" for over 20 years. Ruthy's focus in Arlington and Bedford is applying new energy technologies and big data to assist the towns in lowering their energy consumption in municipal and school buildings while insuring thermal comfort and efficient operations. While not trying to save energy, Ruthy can be found running trails in the summer and playing ice hockey in the winter.

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