Ken Sinclair
AutomatedBuildings.com

Article as published by
 
February 2001

The next phase of building automation technology will bring new life to some traditional equipment. Likewise, it will usher in a rethinking of what building HVAC systems do, and how they do it.  These insights from our building automation columnist can help you get a running start on the new wave of controls.

We have had the ability to use microprocessors for direct digital control (DDC) to enhance equipment energy performance and functionality for several years. However, this power has been locked into islands of automation intelligence in standalone controllers. Although this approach was originally not well accepted by the industry, the islands of automation intelligence are now being bridged with standards in communication protocols. The bridging allows optimum energy and comfort control in large buildings, using a single, cohesive control system with embedded building-wide control strategies.

[an error occurred while processing this directive]The lower cost and increased functionality of combining powerful DDC microprocessors with standard communication protocols is resulting in the componentization of controls for the HVAC industry. Field devices that were traditionally supplied by the control vendor are now appearing as component controllers as part of each HVAC device. This trend is just beginning, but is destined to grow rapidly in the next few years.

Effects On BACnet And LonWorks
BACnet and Lon Protocols are allowing the integration of application-specific component control systems designed for particular HVAC equipment to be included in building-wide strategies. The low-cost componentized DDC's provide functionalities of operation, safety, maintenance and even self-diagnostic information and control. A chiller or a variable-speed drive provides an example of the need for this networked component controller. The ability to make this application-specific component controller part of a cohesive, building-wide control system is now possible because of the acceptance of standard protocols.

In the past since all major HVAC equipment required some type of control system, duplication of control points existed. The acceptance of communication standards has greatly reduced total control costs while increasing functionality by cost-effectively providing information to the users of equipment that was previously only available on the manufacturer's test bed.

We are just starting to scratch the surface on what kinds of functionality can be built into component computerized control. The low-cost, feature-rich DDC microprocessors allow functions and features, only limited by the imagination of the designer, to be added for almost zero cost. If we look at the growth of functionality in chip-type microprocessors like the digital watch or bicycle speedometer, we can get a sense of the types of functionality that can be achieved for a relatively low dollar value. Granted, neither of these devices has to support a communication standard that is the most expensive part of our componentized control systems.

The growth in this area of the control market in the next few years will be phenomenal. As the functionality of component control increases and the cost almost disappears into the fabric of the host equipment, the task of the building-wide system integrator becomes increasingly more difficult. The task of weaving the tremendous inherited functionality in a cohesive building-wide, citywide, countrywide, or even global control strategy becomes very difficult.

Like the digital watch, it is likely that not all embedded functionality will be utilized. A mandatory feature of the new breed of component control and executed communication protocol will be the ability to pull out any connected control points and information.

Standalone equipment with protocol-friendly componentized control, like heat pumps, rooftops, etc., can now be easily and economically integrated into central system control and building-wide strategies.

Not Necessary To Start From Scratch
It is not necessary for HVAC equipment manufacturers to reinvent these powerful controllers. The original equipment manufacturer (OEM) can select from many off-the-shelf products that adhere to standard protocols. Controllers can be easily customized and labeled to closer match OEM particular requirements. This new integration will allow rapid growth with an incredible increase in functionality for the OEM in our industry.

Terminal Control for HVAC equipment will provide the greatest numbers of componentized controllers to our industry. The heat pump's on-off nature has been rejected in the past on quality air conditioning projects. New, low-cost variable-speed control for compressors and fans, coupled with powerful, low-cost component control, is increasing acceptance of this device as a comfort appliance.

In the past, the standalone nature of the heat pump has been both its strength and weakness. The inability to knit the large number of these devices into a building-wide control strategy for energy control, plus the task of ensuring correct operation of each unit has restricted usage. The combining of new functionality and protocol integration is allowing the heat pump to be seriously considered in quality air conditioning projects.

Variable volume terminal devices require complex flow control and adapt well to component control. The advantage of being able to share the flow information in a building-wide strategy allows central equipment optimization and remote maintenance troubleshooting.

Dual-duct dual fan systems are making a comeback, and the complex flow and temperature control of these systems is also enhanced by well-executed, network-friendly component control.

Fan coil control and building-wide integration will be greatly improved with componentized protocol ready controls.

The growth and evolution in the component control industry will see completely new approaches to old problems. The integration of self-diagnostic and self-tuning control loops will grow rapidly. As these features become part of the device, they will increase its total worth.

The concept of connecting these devices to remotely accessible networks will greatly change the present organization of maintenance for major equipment suppliers. The ability to connect simple component controls to server-based diagnostic equipment will bring our HVAC service industries in sync with the way the present automotive engine is computer-diagnosed. This will be a giant leap for our industry with the remote diagnostics of all equipment. When the control component controller fails, the easy installation allows complete replacement to be carried out by existing field staff. Specialist support can again be remote once communications are reestablished.

Pros Of Controls Componentization
Here are some of the advantages created by the componentization trend:

• Overall lower cost because the controls necessary for the safety and operation of HVAC subsystems will be combined with the building-wide control devices. 
• Shared points for safety and operation will be available for building performance monitoring, eliminating the duplication of these points. (For example, the chilled-water supply and return temperatures on a chiller). 
• Shared input information to component control will allow points to be added to the overall system that would not normally be economical to include. Example: power usage of a chiller. This information is necessary for capacity control but could also turn the chiller into its own energy meter. 
• The ability to add increased functionality for an extremely low cost is inherent in component control. The custom-designed controller can have the DDC hardware configuration closely matched to the actual requirements of the HVAC subsystem.
• Closer integration of control in the HVAC equipment can occur through sensors that can be made an integral part of the device by imbedding them in locations not available to field installations. 
• Self-tuning control algorithms will be more successful because timing and tuning parameters can be set for the particular device. Time constants and control characteristics are predictable within the actual device. Factory performance simulation will provide proof of the actual ability of the control to self-tune under any conditions. 
• The fact that this same component control will be used on all manufactured devices will allow the manufacturer the time to closely match correct control for his equipment. 
• Self-diagnostics will be very sophisticated and an integral part of each manufactured device. Using appliance-type thinking and assembly line construction, the component control will be a large part of the quality assurance effort, providing its own device original and continuous performance evaluation. The low cost to add the necessary sensing and functionality to make sophisticated self-diagnostics is achievable and will become the lowest cost of providing original and ongoing product quality assurance. 
• Increased HVAC product functionality will continue to grow as new control concepts are developed daily.

Cons Of Controls Componentization
Of course, there are two sides to every coin, and here some potential disadvantages to the same trend:

• When special functionality is required for building-wide strategies, it will be difficult to get manufacturers to include project-particular control. This will result in the information being networked to a higher level control of building-wide control. This concept moves against the great improvements made in the last few years in providing distributed control at the field level. 
• Distributed control strategies on a building-wide level have the potential to fight embedded component control if the system integrator does not take care. 
• When project-driving problems or design adjustments are required, the rigid nature of the component control will eliminate onsite reprogramming and or customizing for each job. Solutions are likely to be escalated to building-wide control levels, greatly increasing overall programming complexity. 
• Component control will rapidly move to firmware control to become bulletproof and be able to withstand supply power cycling, power spikes, and other project realities. When a problem is confirmed in the component control strategy, this firmness will greatly increase the difficulty of correction. This is of particular concern for terminal control where the numbers are likely in the hundreds or thousands of installed component controls. 
• This same firmness will increase the pressure on the designer to get it right the first time. Equipment suppliers whose main experience may not be in controls will have to provide detailed information to designers and integrators. Any miscommunication could spell disaster. 
• Component control will be a part of each device, and typically these parts will be available only from the original manufacturer. To ensure cost control, module replacement costs should be requested as part of the original equipment selection criteria to eliminate future surprises. 
• Maintenance of HVAC subsystems and their component control may be tied to the original manufacturer because of necessary diagnostic tools and local knowledge. It might be wise to include maintenance costs as part of overall equipment evaluation, or specify open access to necessary maintenance details.

Conclusion
Designers will need to increase their involvement with, and faith in, system integrators who will then be left with the mammoth task of knitting together the myriad of HVAC subsystem component controls within building-wide control strategies.

Component control is here now. We must acknowledge its presence and start planning for its future to help shape its evolution plus integration into our building-wide control strategies. The designers' and system integrators' efforts will be increased as coordination of the selection of all HVAC devices, each with its own component control and communication protocol, presents new challenges. 

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