Role on DDC Systems in Building Commissioning

DDC system capabilities have dramatically increased over the past decades. Their potential role in the commissioning of HVAC systems has improved as well. For example, the following enhancements have made DDC Systems a much more useful tool to the commissioning provider:

  • DDC systems are much more powerful and robust. This allows for more trending, better graphics, and more information available to the commissioning provider.
  • Newer systems are accessible via the Internet, which allows for remote access of the system. In addition, with server-based Internet-based systems, software licensing is not as much an issue.
  • Operator Interfaces (Workstations, notebook computers, and handheld interfaces) are becoming more powerful and less expensive. Typically, they also can connect at more places in the architecture of a given control system network.
  • Graphical programming is becoming more prevalent as a DDC programming tool among vendors, which allows easier off-line simulation of control logic.

With these increased capabilities, has come increased complexity. Over the past 20 years, the controls portion of HVAC systems has undergone the most drastic change of any part of our industry. It has evolved from pneumatic controls to “overlay” energy management systems and first generation Direct Digital Controls (DDC) to current generation distributed DDC. The transition has been rapid and today we find ourselves dealing with control systems that are very different from what was available just a few years ago.

Direct Digital Control of Building Systems: Theory and Practice

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The computer industry’s trend of increasing processing power & memory at a lower cost over time is quickly influencing the DDC controllers as well. The advent of open protocols and increased availability and use of site/building/campus networks has increased the complexity of the design, procurement, operations and the commissioning of these systems. During this time frame, we moved from anon-proprietary communication protocol (air pressure) to one that has been historically very proprietary. In addition, the control logic that was distributed to single function hardware components (receiver controllers, switching relays, etc) now resides in software. These are significant fundamental changes to a critical subsystem of our HVAC system.

This “subsystem” is vital to the performance and basic operation of the overall HVAC system. It historically gets far too little attention in the design, procurement and installation process. The DDC system is the “brain” of the HVAC system. It dictates the position of every damper and valve in a system. It determines which fans, pumps and chiller run and at what speed or capacity.

Yet, proportionally, it receives very little time and attention relative to the rest of the system during the typical design process. Commissioning Providers have both a need and anopportunity to help clarify the DDC systems during the design process so it can be effectively commissioned and become a tool for more efficient and effective commissioning procedures.

Direct Digital Control Systems: Application · Commissioning

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In the ever-changing world of DDC, the focus of design engineers in our industry has been on the new technologies in our business like Open Protocol, Web-based control, interoperability and the like. While these are important issues to consider, we should not lose focus on the more basic, more important aspects that make a DDC system work well. As a commissioning provider, there is a unique opportunity as well as a need and expectation to assist in providing better control system installations. This process begins with the better documents.

Controls and Automation for Facilities Managers: Efficient DDC Systems Implementation

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