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Specifying BACnet





Building Automation

OTHER PARTS OF THIS ARTICLEPt. 1: This PagePt. 2: BACnet: Beyond HVACPt. 3: Pieces of the Green Puzzle
By now, most facility executives are familiar with BACnet, the standard protocol designed to enable various manufacturers’ devices to share data and commands — in other words, to interoperate. BACnet makes it possible to integrate a facility’s various control systems to a single front end for ease of operation. It also allows users to expand and upgrade controls using technology from multiple vendors. This is possible due to common communication infrastructure and front-end building automation systems.

 “Imagine a situation where, in order to connect your DVD player to your TV, the clicker and wires all had to be from one manufacturer,” says Grant Wichenko, president , Appin Associates. “Just as there is a protocol to permit the TV to interoperate with the DVD player, BACnet is the protocol of choice for allowing control system devices to talk to each other.”

Today, BACnet is an integral part of the operation and automation of buildings around the world. BACnet has gained widespread acceptance as a national and international standard. It is formed by a set of software rules, rather than by hardware. The software provides a single-seat interface, which allows control of multiple building subsystems from one workstation rather than relying upon multiple locations or even separate software browsers to provide complete system control.

“Any vendor may develop software that adheres to the standard, and other vendors may share command and control information with other vendors using these rules,” says Jim Herdeman, vice president of sales for KMC Controls. “There is no possibility that the hardware technology will become out of date because there is no hardware at risk.”

Because the BACnet standard is independent, it has been able to evolve over time to take advantage of enhancements and breakthroughs in hardware. Manufacturers of such equipment as chillers and boilers now produce units that have BACnet integrated into the equipment, eliminating the need for hardwiring to the control device. This permits facility personnel and outside contractors to diagnose and correct problems. It also enables different vendors to provide products in the building on a competitive basis.

Automation Road Map

When integrating systems using the BACnet standard, facility executives must define a clear, open-system roadmap for their automation system.

“This roadmap should clearly communicate the interoperability and functionality goals and expectations for all building systems and equipment going forward,” says Roy Kolasa, open system solutions manager for Honeywell’s global offer management team.

The facility executive’s first job is to conduct a detailed examination of automation goals and expectations, then translate them into clear specification requirements that fully define the preferred open system standards for the building automation system and subsystems. The facility executive should develop a list of interoperable equipment and subsystems, including infrastructure drawings depicting the networks and distribution busses on the enterprise system.

The facility executive should also detail what specific functionality is expected from the master system. This should include system points and functionality for control, scheduling and alarming from the master system.

FM and IT

Working in a BACnet environment requires a marriage between FM and IT. “Like a Blackberry or a car equipped with ‘On Star,’ the chiller and the boiler come to the job site as networkable, Web-accessible devices,” Wichenko says. “The controls vendor is now the facilities networking contractor, and the facility executive needs to realize the controls contractor is now responsible for networking HVAC, fire, security and other systems together.”

The facility executive must also decide where the network resides — on the enterprise network or on a separate network maintained by facilities. As maintenance costs rise, it is critical that maintenance staff and outside contractors can access the equipment remotely over the Internet. This enables maintenance costs to be reduced.

“The facility executive needs to educate IT staff as to the impact of having BACnet devices on the enterprise network,” says Wichenko. “BACnet/IP has been designed to permit facility controls equipment to be resident on the network. The bandwidth consumption is minimal as the systems are designed to run on a standalone basis without connection to the network.”

To reduce risk and cost, facility executives also should ensure the controls specification is “vendor neutral,” meaning the language in the spec does not favor one supplier, leaving a facility with field equipment that might provide only proprietary BACnet objects that do not support interoperability.

“Owners should remain cautious because in the interoperable environment, not all functionality is ‘open’ due to some vendors’ desire to maintain ‘proprietary objects’ and functionality that only their teams may utilize,” says Herdeman. “Consequently, not all interoperable protocols are equal.”

Vendor-neutrality is important in the purchasing process. The purchasing department only cares that the bidding is open and fair, regardless of whether one system or numerous systems are installed, but the facility executive should realize that the purchase usually involves an ongoing relationship.

In light of this, the facility executive must consider more innovative options for bidding control work, Wichenko says. A “best value” approach that considers product quality and price allows the facility team to rank features that are most desirable for the organization.

“It’s really no different than buying a car,” he says. “An individual has a certain amount of money in mind and attempts to find the vehicle that most closely meets his needs within the available budget. A best value selection must meet both the needs of maintenance and purchasing.”

Case in Point: Energy Benefits

BACnet interoperability enables communication to subsystems and equipment including variable frequency drives (VFD) and lighting control panels. As a result, managing fans, pumps and lighting systems via BACnet can result in energy savings. BACnet may be used to adjust fan and pump speed, reducing the frequency of these systems to decrease energy use in a demand response control mode or to avoid setting a new peak.

Mike Olson, manager of HVAC applications at ABB Inc., describes a Dallas office tower that uses its building automation system to monitor percent of power of variable frequency drives. A 100 horsepower drive operating at 50 percent power delivers 50 horsepower worth of work through the motor.

If the percent of power of any of the building’s 84 supply or return fans exceeds 50 percent, an algorithm in the BACnet system checks carbon dioxide levels to determine whether the volume of air to the space may be reduced. If so, the system performs a chilled water reset, reducing the temperature of the water delivered to the air handler coils and therefore of the temperature of the air delivered to the space. This action means rooms are satisfied faster, and fan drives slow down further, so the chilled water loop absorbs less heat.

The building has a thermal energy storage system that makes ice at night for daytime cooling. Less heat to reject equals less chiller run time to rebuild the ice for the following day. The combination of the adjustable frequency drives and the chilled water reset strategy produced savings that paid for the installation of the drives in four months.

“If facility executives can review the data and see what the cause and effect is, it will help them initiate change in the energy usage habits within a facility,” Olson says. “Being able to link all systems together and see the data from a single location is one of the best advantages of BACnet.”

 

 

Implementing Demand Response

Demand response control and communication standards and technologies are rapidly evolving to leverage energy flexibility in a facility’s infrastructure. Heating and cooling systems account for between 30 and 50 percent of a building’s energy consumption. This makes these systems key elements in a successful demand response program. Building automation systems provide essential control.

“To have the ability to respond to a demand response event, you have to have the ability to affect the overall control of a building,” says Andy McMillan, president and CEO of Teletrol Systems Inc. “You need internal automation, and BACnet provides the logical components for managing energy use. It provides you an easy way to tell the system to reduce usage, and if the system is designed properly, by how much to reduce it when you receive an alert from the utility. In the old days, the alert came through a phone call. Now, through a Web services (Internet-based) interface with building equipment and the utility, BACnet can achieve this same thing.”

 


Continue Reading: BACnet

Specifying BACnet

BACnet: Beyond HVAC

Pieces of the Green Puzzle



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  posted on 1/1/2009   Article Use Policy

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