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Rantings and Ravings: Why 'DDC' ?
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Rantings and Ravings: Why "DDC"?

    In the past two years, I have noticed the increased use of the term DDC (Direct Digital Controls) in the specifications of HVAC designs. I am in the business. I write programs for digital control systems . But, I have to ask, what is Direct Digital Control? Who is the marketing guru that came up with this term? Please tell me what it means and why we need the term at all!.
          I have to wonder, Direct as opposed to Indirect Digital Controls? How would an indirect digital control interact with an air conditioner? By E-Mail? Memo? Perhaps it would commission a fact-finding committee and wait for recommendations. That would be pretty indirect.
           Or maybe the distinction is to differentiate from Direct Analog Controls. When I close my eyes and try to imagine what Direct Analog Controls are, All I can see is the method of control we have known for decades. That is; pneumatics, mercury-bulb thermostats, brown coated wire, transformers, relays and a "summer-winter" switch. But we never needed a glitzy abbreviation before. The term "Controls" was good enough.
           My head swims when I consider the possibility of Indirect Analog controls. Let’s see … fact-finding committees commissioned by pneumatics… and …pneumatics is the use of air under pressure … AHA! Congress!!
          I think the term DDC is just a new buzzword that is used by people that don't know what digital control is. My recommendation is to suspect anyone who tries to charm you with their vast knowledge by using the term DDC. I would ask the person to describe the "sequence of operation for heating, cooling and ventilation modes". If the person really knows the subject, you will get a precise, lengthy and most likely boring answer! If the person really doesn't know the subject, the response to the same question might be an assurance that the subject is too complicated to discuss right now; or some similar dodge.
           If Washington will share, I would go for the term DC (Digital Control) but that might also be confused with Direct Current. DCC for Digital Climate Control makes sense. DCHVAC for Digitally Controlled Heating Ventilation Air Conditioning is precise if somewhat cumbersome. How about going back to "controls"?   It Seems to fit !


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