Solutions > FDD

The Automated Logic Fault Detection and Diagnostics (FDD) library in the WebCTRL® system can pinpoint over 100 proven faults in typical HVAC equipment,  including VAV systems, air handlers, fan coils, unit ventilators, water-source heat pumps, and air-source heat pumps.

Fault Detection and Diagnostics (FDD)

Pre-programmed FDD algorithms are a standard feature of the WebCTRL® building automation system and will alert building staff of potential equipment issues, help them identify the cause, and provide a visual display of preventive solutions. FDD can help reduce energy consumption, capital costs, and equipment wear and tear.

Detecting and fixing equipment problems can lead to significant savings in energy and operational costs as well as improvements in occupant comfort. A 2013 Australian Summer Study on Energy Efficiency and Decentralized Energy estimated that FDD and ongoing commissioning could reduce building energy use by 17%1. The New Buildings Institute studied 181 buildings in five states and found significant problems in over half the equipment they investigated2.

The built-in FDD capabilities of the WebCTRL system allow building operators to identify and respond to issues when they matter most - before they happen”, said Mead Rusert, President, Automated Logic. “By providing them with analytic tools that uncover potential problems with their HVAC equipment, they can take corrective action before system performance is compromised”.


1 Automated fault detection for persistent energy savings in commercial buildings
Dr Josh Wall | Research Project Leader
March 2013

2 Review of Recent Commercial Roof Top Unit Field Studies in the Pacific Northwest and California
Alan Cowan | New Buildings Institute
October 2004


Building intrinsic analytics into Automated Logic’s WebCTRL®
By Steve Tom, P.E., Ph.D.

This paper provides a brief explanation of which analytic tools are included in the current release of WebCTRL®.

BACnet to the Rescue
By Larry Bacher, LEED® AP

With advancements in the building controls industry, BACnet communication protocol is at the heart of the building automation systems. The following article appeared in ASHRAETM Journal's November 2010 BACnet® Today and reveals how BACnet affected the design of a state-of-the-art, 11-story office building in downtown Boise, Idaho.

Making the Most of Your Building Automation System.
By Steve Tom, P.E., Ph.D.

Former MicrosoftTM CEO Steve Ballmer once indicated that most software users only use about 20 percent of a program’s features. Tom discusses how his experience with building automation systems makes him side with the pessimists.

How FDD Works

Intelligent Alarms

FDD alarms are automatically generated in the WebCTRL® system to warn operators of problems which may be causing equipment to run inefficiently, wasting energy and/or degrading occupant comfort. The Department of Energy estimates FDD alarming could reduce energy use by up to 15%, and the State of California now requires FDD alarming in the Economizer section of certain rooftop units.

Examples of problems that this logic will detect include:

  • Leaking Heating Valves: A worn valve seat or a misadjusted actuator can cause a heating valve to "leak" hot water to the coil even when it is commanded 100% shut. This wastes heating energy and can bring on additional cooling, which wastes cooling energy. The FDD logic generates an alarm if there is a significant heat rise across a closed coil.
  • Failed DX stage In a multi-stage DX unit, if one cooling stage fails, the controls will bring on additional stages as needed to provide the required cooling. The user will not even be aware of the failed stage until the weather gets really hot and the unit can no longer provide sufficient cooling without that stage. Then repairing or replacing that stage becomes an emergency. The FDD logic monitors each stage as it is commanded on, and generates an alarm if any one stage fails to provide cooling. Repairs can be undertaken on a routine basis, while the building is still comfortable.
  • Continuous Running: For a typical building, one of the most effective ways to save energy is to make zones "unoccupied" and turn equipment off at night and over weekends when no one is using the building. Unfortunately, a common problem with building automation systems is the existence of "rogue" schedules, locked points, and other overrides which unintentionally cause systems to run even when unoccupied. These problems often go unnoticed because no one is in the building at the time. The FDD logic monitors zone runtime and generates an alarm if it exceeds a certain number of hours per day. By default the trip point is set at 23 hours, but it can easily be changed to a shorter time for zones that should only be occupied fewer hours.

  • Cascading Alarm Suppression

    Fault Detection and Diagnostics (FDD) uses the power of robust algorithms, hard data and strong reporting of the Automated Logic WebCTRL system. FDD can measure, anticipate, provide insight, and automatically respond to system conditions that are not necessarily critical, but may be trending that way – all with the goal of improved operational performance.

    Always on the cutting edge, Automated Logic is at the forefront of the steadily evolving FDD technology.


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