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Article - September 2002
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Web Accessible Control Systems - Lessons Learned
Web-based systems are not just a concept to be shown at trade shows and discussed in journal articles. They're real, they work, and they are providing unparalleled access to facilities around the world.

Steve Tom, PE, PhD, 
Director Technical Information
 Automated Logic Corporation


As published July 2002
HPAC's Network Controls Supplement


A year ago HPAC ran a series of articles on the Web Accessible Control Systems. (HPAC April/May 2001) At the time, WACS were relatively new and many articles focused on what might be possible with these systems. As the first HVAC controls company to actually bring a web-based system to market, Automated Logic has gained considerable experience with these systems and this article will present some of the lessons we have learned by installing these systems around the world.

Figure 11. Web-based Systems Work. From Shanghai to Newark, in hundreds of offices, schools, museums, data centers, and other buildings, web-based systems are taking care of day-to-day building operations while giving their owners unparalleled access in the process. These systems provide all the functions of a conventional building automation system, including direct digital control of equipment, trending, scheduling, alarming, reporting, and interfacing with other building systems. Unlike conventional systems, however, the user interface is not limited to a few dedicated workstations running proprietary software. Web-based systems generate conventional web pages as the user interface, allowing users to log into the system and perform any required function from any computer on the network. If the network includes the World Wide Web, this means virtually any computer in the world can serve as the operator workstation. If the network includes a Wireless Service Provider, WAP-enabled cell phones and other wireless devices can also be used to access the building system. Obviously these systems also provide a high degree of security to prevent unauthorized access, but authorized users can gain significant productivity improvements from this increased access. Since these systems provide all the functions of a conventional automation system, there is no drawback to this increased access. The custodian of a small public school which has no Internet access can use a dial-up connection to access his system from his home computer, checking on alarms and making needed adjustments without leaving the house. For him, the advantage of a web-based system is that it does not require him to buy multiple copies of proprietary software from the system manufacturer to install on his work computer, his home computer, his neighbor's computer, his wife's laptop, or any other computer he may be near when an alarm comes in on his pager. At the other extreme, customers with world-wide operations can use these systems to access multiple facilities scattered around the globe. Not only does the web access allow them to bring all their facilities together into a unified system, it allows energy managers and consultants located anywhere in the world to access these buildings remotely to study energy usage and "fine tune" the building operation. 

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2. Bring your IT staff into the picture early. Conventional building automation systems have been network based for many years now, and it is not unusual for them to utilize the existing IT (Information Technology) network for at least part of their structure. This has not caused any major problems in the past, but web-based systems introduce at least two new wrinkles into this situation: 

a. They have the potential, at least, to provide outside access to the existing IT network, and 

b. They utilize technologies and devices such as web servers, routers, and IP addressing, which are traditionally the province of the IT department. 

Neither of these issues is insolvable, and in fact the "solution" is often simply a matter of providing the IT department with the proper information. They are, however, reasons to involve the IT staff when planning to install a web-based system, and it's best to bring them into the picture as early as possible. 

PlantPROCORE Conventional control servers tended to use proprietary hardware and proprietary terminology, which was of little interest to the IT staff. If you wanted to install an operator workstation and a few primary controllers on their network, you were no different than the hundreds of other users installing PCs and network printers. Replace that operator workstation with something called a Web Server however, and it's an entirely different situation. Now you're treading on IT territory and they are intensely interested. Their interest is understandable. Professionally speaking, the IT network is their sole reason to exist, and they live or die based on how dependable that network is. Anything that has the potential to disrupt that network is of great interest to them. In actuality, a properly configured web-based system does not pose a threat to their network. There are many ways to provide security for a web-based system, as will be explained in the following section, but it is important to involve the IT staff in the planning process early so their concerns can be addressed. If you "surprise" them by hanging a web server on their network without consulting them in advance, they are bound to get defensive and create all kinds of obstacles. (The reaction of a mother bear with cubs that is surprised by the appearance of hikers is nothing compared to an IT staff that is surprised by the appearance of a web server.) 

3. Address security concerns early. Whenever a system can be accessed by "outsiders," security needs to be addressed. There is nothing unique about web-based control systems in this regard. Indeed, conventional control systems with dial-up access also have the potential to be "hacked" by outsiders. In many ways, web-based systems have an advantage over conventional systems in that they utilize Internet technologies and can take advantage of the security systems that have been developed to protect bank transactions, personal information databases, and other sensitive data that is routinely transmitted over the Internet. The list of customers who use our web-based system includes universities, military bases, financial institutions, telecommunication centers, and others who have reason to be especially careful about security. Again, the key is to involve the IT security personnel in the planning process, and address their security needs up front. Factors to consider include: 

Figure 2a. Use a "fine-grained" password protection scheme. Passwords have long been used as the first line of defense for conventional building automation systems, and web-based systems are no different. A "fine-grained" password protection scheme allows you to adjust the access levels for each individual operator to give them access to the equipment and properties they need, and to prevent them from accessing anything else. This type of system will allow you to control access to setpoints, schedules, tuning parameters, hardware configuration, and other sensitive functions. Operator privileges can be controlled from "view only" to full system administrator rights, depending on the needs and experience of the individual operator.

b. Use a web server which is inherently limited. There are "general purpose" web servers available on the market which are designed to provide web access to a wide range of network functions, often as an "add-on" to an existing database. Unfortunately, the widespread use and wide range of features of these servers also makes them very popular with hackers. We use a dedicated web server which is built into our product and which only provides access to the building automation functions. Additional security is provided by only activating the port needed to access web pages. (Typically port 80.) By not activating the ports needed for Telnet, NetBios, FTP and other network functions, the potential for unauthorized access is greatly reduced. 

c. Use encrypted transmissions. Secure Socket Layer (SSL) connections can be used to provide 128-bit encryption on all transmissions between the browser and the web server. This effectively prevents anyone from tapping into your communications to capture passwords and other sensitive data. SSL is commonly used to protect Internet credit card transactions, and this same level of protection should be available on your web-based control system. 

d. Use Firewalls and/or Virtual Private Networks. The WACS server should be compatible with external firewalls and Virtual Private Networks (VPN) to provide additional security. VPN can be configured to restrict access to specific computers which have been individually configured as a member of the VPN. Computers which are not a designated member of the VPN cannot connect to the network, regardless of any passwords or "inside knowledge" the operator may possess. 

e. Restrict your system to an intranet. While the term "Web Accessible Control System" implies a connection to the World Wide Web, this connection is not required in all cases. While not connecting your system to the Internet does reduce the "access from anywhere" advantage of a WACS, the system is still available from any computer on the internal network. Universities, data centers, and other customers with a 24/7 facilities staff may find this is an acceptable trade-off since their on-duty staff still has full access to the control system. 

The security arrangements needed for any particular installation will depend on the security needs of the customer. Not all of the provisions outlined above need to be implemented in all cases. A careful review of the trade-offs involved with each option needs to be reviewed when planning for a particular installation, but the bottom line is that web-based systems can be made as secure as needed. 

4. The use of open protocols enhances the interoperability of WACS. Web-based systems typically utilize Internet standards such as HTML for generating and transmitting web pages. These Internet standards are designed to render computer data as text and graphics which can be understood by humans. While this allows operators to access multiple systems through a single web browser, these Internet standards do not provide interoperability between different pieces of equipment within the building automation system. Fortunately, WACS can be fully compatible with existing standard protocols for equipment, such as BACnet, LonWorks, or Modbus. Using these protocols within the WACS greatly simplifies the integration of equipment made by different manufacturers into a unified system, and the WACS interface makes this system available through a web browser. Status values, setpoints, PID gains, and other commonly accessed values can be presented in a unified front end that shields the operator from having to learn a different interface for each vendor. BACnet adds higher level functions such as scheduling, trending, and alarming to this mix, making it even easier to manage the entire system from a single front end. While all of these functions can be integrated without the use of an open protocol, the use of open protocols eliminates the need for custom programming and greatly simplifies integration. A few examples: 

a. A government facility manager uses BACnet to integrate 11 buildings in 3 states using control systems made by 4 different manufacturers into a single energy management system. Five of the buildings were controlled by native BACnet systems to begin with, while six use proprietary systems which are translated into BACnet through a gateway. The net result is a unified interface which allows operators and consultants across the US to view and manage energy data through their web browsers. (Interestingly, the WACS system that unifies this network was made by a 5th manufacturer, further illustrating the interoperability provided by open protocols.)

Figure 3

Figure 4b. The Shanghai ScienceLand Museum, in Shanghai China, uses BACnet to integrate 3,200 control points and 1,000 monitoring points into a single WACS. AHUs, chillers, pumps, lighting, elevators, fire, security, and other building systems supplied by 9 different vendors are monitored and controlled by a unified operator interface.

c. The Houston Bush Intercontinental Airport is using a WACS to integrate two native BACnet systems plus multiple Modbus systems into a single, unified system. With construction nearing completion, it is safe to say this integration could not have been completed within the time and budget available without the use of open protocols.

In conclusion, web-based systems are not just a concept to be shown at trade shows and discussed in journal articles. They're real, they work, and they are providing unparalleled access to facilities around the world. The planning and implementation suggestions described in this article can make the installation of these systems go more smoothly, and can help you decide if a web-based system is right for your operation.


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