The DDC system, ClearControl™, by Rheem manages and reports over 100 system functions communicated on a 16-character LED screen making jobs faster, easier, and more profitable for contractors.

Information increasingly drives our personal and professional lives. An ever-changing menu of new data exchange tools like smart phones, iPads, web conferencing, and various wireless gadgets make the globe’s information totally and instantly accessible. While the vastness of information may sometimes be overwhelming, when it is delivered in an easy-to-read, customized manner, it can make us more productive, efficient, satisfied, and successful.

Many of the same technologies that deliver this information to our fingertips have made their way into how commercial HVAC equipment is understood, specified, and installed. This streamlining of commercial HVAC system information allows professional contractors to receive data critical to accurately diagnose technical performance, determine appropriate action, and quickly and precisely implement corrective procedures. Immediate access to accurate technical data, combined with the training and professional expertise of the contractor, virtually eliminates costly and time-consuming guess work and trial-and-error methods. The results are significantly improved customer satisfaction, less time per job, and improved contractor profitability.


There are two basic types of commercial HVAC package equipment on the market today: equipment using electromechanical controls (EMC) and equipment using direct digital control (DDC) systems. The biggest difference in these two types of systems is the way in which vital system and troubleshooting information is delivered to the contractor or end user.

Prior to 1990, when a technician installed or serviced a standard EMC package system, his primary diagnostic tools were gauges, a multimeter, and a power drill. Diagnosing and servicing these units could prove to be a time-consuming and costly series of “try this” and “try that” based on deductive reasoning. The more veteran and experienced the technician, the more likely it was that an expedited, less costly solution would be found.

In the early 1990s, microprocessor-based controls emerged on the scene, heralding the era of DDC packaged HVAC systems. Initially, package gas-electric units combined multiple mechanical controls into an integrated microprocessor control board on the heating side of the units.

Generally, information was communicated to the contractor through a blinking LED that would pinpoint where an issue was most likely occurring. Eventually, some of the controls were also integrated into the cooling side of the package system. Each step made diagnostic information easier to obtain when installing or servicing the package unit, leading to increased accuracy, improved installation and service quality, reduced time-per-job rates, and improved profitability.

While EMC products are still used by some today, the growth curve for the adoption and preference for DDC technology is accelerating at a fast pace due to increased DDC system affordability. Commercial HVAC business owners and technicians are increasingly realizing that the initial cost differences are greatly outweighed by the advantages of quick, accurate diagnostics in an easy-to-read format that can be effectively implemented on the job by less senior technicians.

Another technical evolution has occurred inside the package unit. Each package unit is now controlled directly through digital signals, which communicates information from one control to another. This real-time information can be communicated between multiple package units, or through the use of a graphic user interface (GUI) to an onsite computer or one located across the globe.

The Rheem Commercial Series™ package gas-electric rooftop unit has factory-installed ClearControl™, direct digital control (DDC), and sensors can connect to LonWorks™ or BACnet® BAS systems for remote monitoring and control.


Although today’s control boards may not have the sleek appearance of the iPhone, they have taken a cue from today’s advanced home electronics. Fingertip navigation and text have replaced blinking lights, flashing numbers and confusing codes, eliminating the guesswork and incidence of misdiagnosis due to error when a contractor had to count the number of times a tiny LED light had blinked to determine the fault code.

This ability to easily share information has ushered in a new era in package equipment professional installation and service. Troubleshooting information is now literally at your fingertips. The availability of DDC system information enables junior and senior commercial HVAC technicians to spend less time per job, increases the number of service appointments per week, reduces the number of callbacks or equipment failures due to misdiagnosis, and increases productivity and profitability.

Open protocols such as Bacnet® and LonWorks® have become commonplace and economically feasible on smaller jobs by allowing multiple mechanical systems to communicate on a common network. The increase in the use of open protocol languages can even eliminate the need to physically climb to a roof and open a unit to complete an effective diagnosis. When a DDC system is used between HVAC controls and open protocols, building management systems can display vital system information over the Internet, either on- or off-site.

Although working on an HVAC package unit may not be as intriguing as playing with hundreds of apps on your smart phone or winning the PGA Tour on your Wii®, the technology that delivers all the information to these devices is becoming more common place and can certainly be expected to be found in commercial HVAC package equipment in the future.

Publication date:06/14/2010