AutomatedBuildings.com Column - Paul Ehrlich & Ira Goldschmidt

Several years ago we had the unique experience to be members of an ASHRAE committee that was charged with developing a guideline for specifying DDC controls. Committee work is often frustrating, involving volunteers with different perspectives and levels of involvement and this project was no exception. We met twice a year for over ten years struggling to define the purpose, then to create a guide spec, and finally to write a guideline that explained how to use the document. While this was often frustrating, it was also fascinating to be involved in the dialogs that went on between committee members who represented owners, consultants, contractors and suppliers. We had good spirited discussions about what went into a specification, how they where interpreted, and what was necessary to assure a successful project. In the end we completed what is now ASHRAE Guideline 13.

Spending this much time and effort focused on this topic resulted in several key lessons learned which are still very relevant today. We learned a lot about not only the end result but also the process that goes into the development of a good controls design. So what where the key lessons?

Often we think of the design of the controls system as being reflected in the controls specification. This is rarely the case. In fact a good controls system design will have four key elements which include:

Of these elements the first two are the most critical for the successful design of a control system. Yet surprisingly we more and more are hearing about projects where these are either not properly completed, or in some cases omitted all together, instead suggesting that the contractor should determine the proper sequences and/or points. It is also important that these elements be properly coordinated so that they don’t contradict or overlap with each other.

Often we are asked for “the controls spec”! In reality the design of the controls system really starts with the selections made for the mechanical and electrical systems and a good understanding of how the building will be operated. Buildings that are standalone will need a different solution then those that are part of a larger enterprise. Systems need to be properly selected and designed. More and more often we are designing sophisticated control systems with a high degree of systems and business integration. But while these may be the right solution for a sophisticated owner, they aren’t right for simpler, more basic projects.

Ideally we like to see the key elements of a controls system be specified so that the system can be competitively bid and the performance can be verified. This means ideally that the key performance parameters are clearly specified in a generic fashion (building automation technology does not lend itself to the practice of “basis of design” specifications which works well for mechanical equipment). By using a performance perspective, we allow the contractor to be more creative, have key elements that can readily be enforced, and end up with a more streamlined specification.

Next Month
The topic of controls specification development will continue next month with a discussion of proper documents, interoperability, and when prescriptive language is required.

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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