The HVAC portion of the America West Flight Simulator Building, in Phoenix, Arizona, was an innovative and challenging project in which a truly Open Control System was put to a real world test. We have all heard the sales pitches from the various manufacturers about their system being "Open", with the ability to communicate with other such "Open" systems on the market, but the time had now come to put up or shut up.

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The first step was carefully selecting potential equipment and control vendors for the various applications on the project: Computer Room Units, Chillers, Pumps, Air Handlers, VAV Boxes, Variable Frequency Drives, Exhaust Fans, and Cooling Towers. The equipment vendors had strict performance guidelines to match, and were required to provide equipment that would communicate directly with the controls. This sounds deceptively easy (Open Protocol is a concept that has been around for years, with many pretenders to the throne of success), but in fact was not easy since true Open communication between equipment and controls is actually quite new. Smith Group's Engineer Jay Robins had the principal task of evaluating all the potential equipment and control suppliers that would compete for the Challenge/Privilege that was ahead of them. Once the design and selection process was complete the Specifications and the plans went out for bid.

The equipment and controls were chosen through the normal bidding process, with McQuay selected for the Chillers and Air Handlers, Reliance for the Variable Frequency Drives, Evapco for the Cooling Towers, Liebert for the Computer Room Air Conditioning, and Honeywell for the Energy Management System (controls).

With any new protocol (communication language) there is a risk involved and a learning curve associated with that risk. Climatec Building Technology Group (BTG) made the decision to step up to the plate and demonstrate that Open communication can work, that it actually does have real world applications. At Climatec BTG we have worked with various Open Protocols --- BACnet, LONWorks, Modbus, DDE, TCP/IP --- but never with such a high level of real integration brought together on one platform. With the help of Honeywell we incorporated Honeywell's new SymmetrETM Building Management System to accomplish the task of integrating all of the Open Protocols on the project into a single front-end solution.

The design of the controls was based on taking all of the Open Protocols to the front-end with integrating functions forming an Intelligent System. Through this Intelligent System a vast amount of information is delivered to one central Operator Workstation (OWS) Computer, creating a Facility Management Tool that greatly enhances the Facilities Management Team's control and monitoring of their HVAC system. An Echelon LONWorks communications backbone (utilizing LON routers provided by Engenuity) connects the VAV Boxes, Air Handlers, Cooling Towers, Pumps, and Exhaust Fans using LONWorks Open Protocol controllers. The Liebert Computer Room Air Conditioning Units and the McQuay Chillers have on-board controllers that use Modbus Open Protocol for communication. Both networks are brought back to the Honeywell SymmetrETM front-end where the America West Flight Simulator Facilities Managers are able to access their entire HVAC System.

[an error occurred while processing this directive]With the help of McQuay, Real Time Automation (RTA), and Honeywell, and through many hours of testing in the field, we were able to use the Modbus Open Protocol to control and monitor the Chiller points. From the OWS the operator can view points (such as evaporator pressures, temperatures, and current draws for the individual compressors) internal to the building's dual-compressor McQuay Chillers. All of these points are available over a two-wire network to the OWS for a fraction of the cost of installing sensors in the field, and there is the added benefit of having the point information at the OWS be the same as that seen at each Chiller's on-board controller.

With the help of Reliance and Honeywell --- and many more hours of testing --- we were also able to control and monitor points internal to the Reliance Variable Frequency Drives using the LONWorks Open Protocol technology. A total of 14 VFDs were installed on the project to control motors on the Secondary Chilled Water Pumps, Cooling Tower Fans, and Air Handler Supply and Return Fans. Through direct tie-ins to the LONWorks communication bus, each VFD is integrated into a control sequence over a network and shared with other controllers. Points include speed control, demand limiting control, drive status and alarm, power factor, current draw, and phase loss, as well as a variety of Energy Management features. Some of these points and features were available in years past, but only through expensive PLC controllers. At America West Flight Simulator the Secondary Chilled Water Pumps, Cooling Tower Fans, and Air Handler Supply and Return Fans are all operated and viewed over a simple pair of wires using Open Protocol.

Honeywell Excel 5000 LONWorks controllers automatically operate the VAV Boxes, Central Plant, Exhaust Fans, and Air Handlers. The same pair of wires that are used to communicate with the Reliance VFDs are also used to communicate with the 200+ VAV Boxes, and with the Central Plant, Exhaust Fan, and Air Handler controllers throughout the America West Flight Simulator Facility. Points internal to the individual Honeywell controllers can be viewed and controlled at the OWS as well as incorporated into Energy Management Strategies with other Open Protocol Devices.

Cooling for the computers at the actual Flight Simulators is supplied by Liebert CRAC Units, which are automatically operated by Liebert's on-board controllers. In similar fashion to the McQuay Chillers, the various points available at each Liebert CRAC Unit can also be viewed at the OWS. The Facilities Managers can thus proactively respond to problems before they have a chance to become full-blown crises.

The project learning curve was steep, and the road to success hard, requiring the cooperative efforts of all the parties involved. In the end, though, the original vision was realized, with a truly integrated HVAC System controlled and monitored through a single front-end. The bottom line is that Open Systems are the way of the future, and this project proved that they could be affordable and reliable. 

Author - Bill Simpkins has worked in the DDC industry for 15 years starting as the panel builder and working up the ladder as a Designer/Cadd Operator, Engineer, Sales and now Sales Manager.

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