FOUNDATIONS A B A C n e t I N T E R N AT I O N A L P U B L I CAT I O N
SEPTEMBER 2015
INCLUDED INSIDE:
A Case for BTL Testing
BACnet Developers Q&A
I am a VFD and I Speak BACnet
www.bacnetinternational.org
FOUNDATIONS — A BACNET INTERNATIONAL PUBLICATION
Overview The Foundations publication is an educational resource produced by BACnet International for its members. BACnet International is the cornerstone of your success, and Foundations builds on that by providing the technical knowledge you need to success in the world of building automation. Foundations is written by volunteers from the BACnet community for integrators, installers, appliers and specifiers/consultants. It complements the BACnet International Journal and the association’s monthly enewsletter, Cornerstones.
For more information on BACnet International, please visit www.bacnetinternational.org.
Questions or article submissions may be directed to BACnet International Communications and Community Manager Erin Hall at erin@bacnetinternational.org
FOUNDATIONS — A BACNET INTERNATIONAL PUBLICATION
Table of Contents A Case for BTL Testing By Kate Johnson Business Strategy and Communications Consultant ......................................................................................... 2
BACnet Developers Q&A By Steve Karg Senior Engineer, WattStopper ............................................................................................................................ 5
I am a VFD and I speak BACnet By Tim Skell Senior HVAC Application Engineer, ABB Inc...................................................................................................... 7
Success Story: Ohio University By Steve Jones Managing Partner, The S4 Group, Inc. ............................................................................................................... 9
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A “Small Closet” Case Study Kate Johnson
Business Strategy and Communication Consultant
B
TL testing can save time and money by verifying both conformance to the BACnet specification and the required interoperability to perform well in real-world, multi-vendor implementations.
The BACnet® Testing Laboratories (BTL) Mark is granted to those products that have passed rigorous testing against the BACnet standard for both compliance and interoperability. Testing is performed by several independent testing labs that have been recognized by BACnet International. The BTL Product Listing only includes products that have achieved the BTL Mark. The current BTL Product Listing includes more than 600 products from more than 100 manufacturers. With the wide range of BACnet products available, what value does the BTL Mark truly add to suppliers, integrators and users? Interoperability The BTL Mark indicates defines more than just conformance to the BACnet spec. It also indicates a level of confidence about interoperability. While interoperability is the goal of all BACnet products, internal testing alone may not be sufficient. A device’s Protocol Implementation Conformance Statement (PICS) describes the BACnet options that are implemented in that device. However, the PICS alone is not a guarantee that the implementation is successful. The BTL® Mark is more than marketing. It’s insurance. The Scene The building was a childcare facility associated with a local university. The installed products were was a variable refrigerant flow (VRF) system and a Siemens BACnet IP building controller. The goal was to “route” the VRF system operating information through the Siemens controller up to a facility front end PC located in another building for monitoring and alarming of the VRF system information. The Integrator Pete Howard is a very experienced technical specialist who has worked for Siemens for over 20 years. The Expectation “I looked at the PIC Statement for the…[VRF system] software and read through its interoperability definitions, and it said everything I wanted it to say as far as I should be able to connect to it and pull data from it,” said Howard. “But it wasn’t BTL stamped, and I had missed that.” The Challenge: Who-Is and the Surprise of No Reply The device would reply to a Who-Is when broadcast locally, but not from another subnet. Howard used Wireshark® to capture network communication when broadcasting Who-Is on the local subnet and was able to see the device reply as he expected. And then he used Wireshark captures of Who-Is broadcasts on the remote subnet and was able to verify that the device was simply not replying.
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“Why would it answer to a “Who-Is” when that broadcast message was sent from its local subnet, but not answer “Who-Is” when broadcast from my server, which was on a different subnet?” After more than a week of Wireshark captures and consultations with two representatives from the other company, one who flew in from overseas, it became clear to Howard and his colleagues from the other vendor that the other vendor’s product was not handling routing as it needed to. This was a relatively straightforward routing issue that would have been caught during the BTL testing process. “BTL would have picked up on the fact that this device wouldn’t answer forwarded MPDU packets.” “My mistake was assuming that once I got that PIC Statement, that it had been BTL tested and certified, however it had not been tested for that particular installed software rev, “said Howard. “And…their lack of interoperability prevented me from pulling the device in across two different subnets…” The Solution The remedy? A simple software upgrade to the VRF interface. The Impact “Besides the initial contractual start up and coordination, there was easily a week’s worth of testing, troubleshooting, and analysis before the issue was fully resolved, and this doesn’t account for the [other vendor’s] time and associated travel costs,” Howard said. “They first sent up a field rep…without fixing the issue, then sent a factory rep from [overseas] before the issue was finally resolved.” How much did all of that extra time cost? Between the two vendors, Howard estimates the cost to be at least $10,000. Not to mention the time he spent holed up in a small closet, the significant travel expenses incurred by the other vendor, the schedule impact of an extra week of troubleshooting and the unnecessary stress for everyone involved. The Bottom Line There is significant value of the BTL Mark to both users and suppliers in terms of managing expectations, minimizing costs and avoiding schedule slips. A common goal between BACnet International and suppliers is to provide interoperable products at the lowest possible costs. The goal of the BTL testing, the BTL Mark and the BTL product Listing is to verify device performance against the intentions stated in the device’s PICS. The cost of BTL testing is incremental in the overall product development cycle, and can save time and money in installations by verifying both conformance to the BACnet specification and the required interoperability to perform in real-world, multi-vendor implementations. Common Sense Caveat While BTL testing reduces integration time and costs, choosing BTL Marked products and devices cannot overcome poor system design. Poorly engineered systems will likely perform poorly. Applications and implementations need to be designed well. And consulting engineers and integrators need to be discerning, understanding the positive impact that BTL Marked products and devices can make in supporting a positive outcome. Acknowledgement The author thanks Pete Howard of Siemens for his generous sharing of this case study. Trademarks Wireshark® is a registered trademark of the Wireshark Foundation. wireshark.org
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BACnet Testing Laboratories (BTL) and the BTL Mark are registered trademarks of BACnet International. ABOUT THE AUTHOR Kate Johnson is a business strategy and communication consultant. Drawing from her background in engineering and her irrepressible creativity, Kate specializes in assisting technical companies successfully navigate times of transition. Discover more at www.katejohnsonconsulting.com.
BTL FAQ Why does BTL testing matter? The rigor of BTL testing enhances interoperability of the selected devices, offering peace of mind to the integrator and the user. BTL testing results in reduced integration challenges and associated costs for users through reliable systems operation and implementation as well as providing some level of future proofing as products get updated and advance along with the BACnet standard. Testing results in better products—pre-testing tends to drive discovery and improvement opportunities—leading to a higher level of confidence for prospective customers, shorter sales cycles, and a lower burden of proof. What does the testing cost? Suppliers have a choice of recognized test organizations with different pricing models. In general, test costs are based on an hourly rate with some test organizations providing discounts for select BACnet International corporate members. For most products, the cost of BTL testing is a small part of the total development cost and is more than offset by the savings from finding problems earlier in the product lifecycle.
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What does it cost to use the BTL Product Listing? There is no charge for using the BTL listing to search for tested products. Membership in BACnet International is not required, though it is encouraged. What Testing Tools Exist? A variety of pre-testing tools and services are available to suppliers including a BACnet test framework (BTF), and a free Visual Test Shell (VTS) tool by which you can exercise your device. In addition, the BACnet Testing Laboratories Working Group hosts an annual PlugFest, which is a neutral, closed-door, international technical jam session where suppliers can bring devices and test with products of other participants. These tools assist suppliers in delivering BACnet products that conform to the specification and interoperate with products from other manufacturers. For more information: For more information on BTL testing services, BTL product listings, and pre-test support, go to www.bacnetlabs.org or www.bacnetinternational.org.
FOUNDATIONS — A BACNET INTERNATIONAL PUBLICATION
BACnet Developers Q & A By Steve Karg
Senior Engineer, WattStopper Editor’s Note: Marketers Rush In Where Engineers Fear to Tread An anonymous member of the BACnet International Marketing Committee defines ‘native’ as a product, which was conceived, designed and produced to communicate via BACnet versus products, which may add BACnet communications to an otherwise proprietary platform.
Over the years while being involved in the BACnet committee and developing BACnet products, I have fielded questions about BACnet product development. Some of those questions are answered by the official BACnet Testing Laboratories “Implementation Guidelines.” However, some questions are beyond the general scope of that document. Those questions—and their corresponding answers—are addressed in this article. Q1: Why does Multi-state Input object Present_Value property not accept a value of zero? What is up with this filter? A1: In addition to Present_Value, the multi-state value has a property called State_Text, which is a BACnetARRAY[N] of CharacterString: From the BACnet standard, ASHRAE 135-2012: 12.18.4 Present_Value This property, of type Unsigned, reflects the logical state of the input. The logical state of the input shall be one of ‘n’ states, where ‘n’ is the number of states defined in the Number_Of_States property. The means used to determine the current state is a local matter. The Present_Value property shall always have a value greater than zero. The Present_Value property shall be writable when Out_Of_Service is TRUE. Any local modification to the value of the Present_Value when the Number_Of_States property is changed is a local matter. ... 12.18.12 State_Text This property is a BACnetARRAY of character strings representing descriptions of all possible states of the Present_Value. The number of descriptions matches the number of states defined in the Number_Of_States property. The Present_Value, interpreted as an integer, serves as an index into the array. If the size of this array is changed, the Number_Of_States property shall also be changed to the same value. A BACnetArray element 0 returns the number of elements in the array: 12 MODELING CONTROL DEVICES AS A COLLECTION OF OBJECTS ... A “BACnetARRAY” datatype is a structured datatype consisting of an ordered sequence of data elements, each having the same datatype. The components of an array property may be individually accessed (read or written) using an “array index,” which is an unsigned integer value. An index of 0 (zero) shall specify that the count of the number of data elements be returned. If the array index is omitted, it means that all of the elements of the array are to be accessed. An array index N, greater than zero, shall specify the Nth element in the sequence. When array properties are used in BACnet objects, the notation “BACnetARRAY[N] of datatype” shall mean an ordered sequence of N data elements, each of which has that datatype. The datatype of array element 0 is Unsigned. If the size of an array may be changed by writing to the array, then array element 0 shall be writable. If the value of array element 0
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is decreased, the array shall be truncated and the elements of the array with an index greater than the new value of array element 0 are deleted. If the value of array element 0 is increased, the new elements of the array, those with an index greater than the old value of array element 0, shall be created; the values that are assigned to those elements shall be a local matter except where otherwise specified. Where the size of an array is allowed to be changed, writing the entire array as a single property with a different number of elements shall cause the array size to be changed. An attempt to write to an array element with an index greater than the size of the array shall result in an error and shall not cause the array to grow to accommodate the element. Arrays whose sizes are fixed by the Standard shall not be resizable. Therefore, the Present_Value state cannot have a value of 0 since the Present_Value, interpreted as an integer, serves as an index into the State_Text array. Q2: We have been questioned whether our BACnet device is native or non-native. I have no idea what this term means, and there is no mention of it in the BACnet protocol standard. Could you shed any light on this terminology? A2: There is small mention of “Native BACnet Systems” in the following article: http://www.bacnet.org/ Bibliography/ASH-3-98/ASH-3-98.htm. “New and existing installations use BACnet for all aspects of communication, including workstation, field panel, custom application controller and unitary controller communications and are commonly referred to as native BACnet systems.” The BACnet committee debated “Native BACnet” vs “BACnet Gateway” for many years, and even tried to nail down the definition. The proposal “DMF-034” by David Fisher initially defined “Native BACnet Device” as “a BACnet device that uses BACnet for communication. A BACnet device may also provide gateway functionality and still be described as a Native BACnet device.” The subsequent debate in committee changed the definition to “a BACnet device that uses BACnet for communication. A Native BACnet Device represents a grouping of physical and logical inputs and/or outputs whose value and status are represented as BACnet object properties. The physical measuring inputs and/or actuation outputs are intended to be part of, or in close proximity to, the BACnet device. The totality of input/output hardware is considered to be a single Native BACnet device so long as the detached input/output hardware cannot be used or sold by itself for any other purpose.” The committee debated the proposal, but there was still not consensus on where a vendor draws the line between the BACnet stack and its connection to its I/O or other object property values and behaviors. The discussion was tabled in 2007. Therefore, there currently isn’t any standard definition of the term “Native BACnet”. There is a standard definition of a BTL listed device, however, and that is the only standard type of BACnet device defined. Q3: I need to be able to detect whether a point is writeable or not, but can’t find a definitive reference on how to detect this in the BACnet standard. It does state what properties are required to be writeable/readable/optional, but it does also state: “Such R (Readable) or O (Optional) properties may also be writeable at the implementor’s option unless specifically prohibited in the text describing that particular standard object’s property that vendors can still choose to make it writeable.” A3: Unfortunately, there isn’t an easy way to know if a point is writable, other than asking the vendor to provide you a list of points in some easy to use format. Someday there may be XML files referenced by the device, which will show which properties are writable, but that is still in discussion. The accepted way to determine writababilty, at the moment, is to read the property value, write the same property value back, and see if there are errors indicating the property is not writable.
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ABOUT THE AUTHOR Steve Karg is a senior engineer at WattStopper, in Birmingham, Ala. He has been an active member of ASHRAE SSPC 135 (BACnet) since 2001, and convenes their Lighting Applications Working Group. He wrote an open source BACnet Protocol Stack hosted on SourceForge.net, and continues to help maintain the BACnet decoder in Wireshark.
I am a VFD…and I Speak BACnet By Tim Skell
Sr. HVAC Application Engineer, ABB Inc.
H
ello, I am a variable frequency drive (VFD), and I speak BACnet. I, as well as many other VFDs, were manufactured with BACnet embedded as a standard feature. There is an incredible amount of information in me; all you have to do is ask. What you do with that information and how to take advantage of it is an important topic, which will be addressed in future BACnet publications. You can ask or tell me things at whatever speed you prefer. Should we have our conversation at 76.8 kB? Or is that too fast for the others who want to participate in this conversation? That is OK; 38.4 kB also works. While sometimes my brother and sister VFDs are up on the BACnet IP side of things, you’ll typically find me hanging out at the MS/TP corner bar. Other than a few of my in-laws, we have all gone to school and graduated with a BTL certification, so you know we are capable of playing nice together on the wire. While we would all like to live in a perfect world where everything works on the first attempt, we know that is not always the case. So, I would like to tell you about a few hardware topics that can cause issues and make it more difficult to talk to me. And no, it has nothing to do with the fact I may be a bit grumpy because that attractive touchscreen wouldn’t give me her MAC address last night at the MS/TP corner bar. Wiring Practices As a VFD, my internal workings are quite complex. Most people don’t realize that when I run a 460 VAC motor, I’m actually producing 650 VDC and switching it on and off 4,000 times a second. So, do you think it would be a good idea to route the low voltage BACnet wire near the motor wires? Of course not, but not everybody is as intelligent as those who read BACnet Foundations solely for its articles. Do not forget about the shield. The ability to daisy chain on MS/TP wire is very useful and simplifies installations. The shields at each junction must be connected together to maintain electrical continuity through the entire length of the shield. The shield should be earth grounded only at one end, which is typically back at the controller. Wiring Type Did you know the BACnet MS/TP standard (aka ANSI/ASHRAE Standard 135) states that you should use three wires when communicating to an isolated device? And guess what? I am an isolated device. You would not believe how many times people come up to me with their twisted pair and a shield, with no third wire to be seen.
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Or even more frustratingly, I will see them bring the third wire to me, but they don’t actually land it on my reference terminal. Normally I can deal with a twisted pair just fine. Nevertheless, if there are other problems going on, the fact I don’t have a third wire connected could magnify the problem. Think of the third wire— which is a reference wire—as an insurance policy that could help cover up noise issues, or perhaps poor wiring or grounding practices. Be aware that some of my older cousins—the front-end controllers who like to boss me around—do not always have a landing location for the reference wire. There are several ways to work around this, depending on which family the controller comes from. Biasing My momma raised me right; I am not a biased VFD. The BACnet MS/TP standard requires the wire to be biased. Most (but not all) front-end controllers are capable of biasing the wire. “What happens if the wire isn’t biased,” you ask? Let us say 12 of my VFD buddies are hanging out and having a great conversation at the corner MS/TP bar. Now four more folks come in and join the conversation so there are 16 of us. But suddenly, I can’t hear two of the original VFDs, it is as if they aren’t talking. I know they are sitting there, I physically see them, but they don’t respond. Had the wire been biased, we wouldn’t have had this problem. Now we need to order up some additional hardware to bias the wire. Devices on a Wire After a hard day at work, everyone wants to go down to the MS/TP corner bar. We must be careful not to upset the fire marshal by exceeding the maximum occupancy limit for the bar. Serial communications hardware is different in various products. For example, one VFD may have a 1/8th drop transceiver, while another has a full drop transceiver. Assuming no other devices other than the main controller, a total of 255 1/8th drop devices can be on a single wire, while just 31 full drop devices could be on a single wire. BACnet is the most prevalent HVAC communication protocol used in the market. VFDs are in most HVAC applications. An intelligent automation system may be achieved by using BACnet to properly integrate VFDs into the system. A system with VFDs is more likely to function seamlessly by following the above recommendations. I am a VFD, and I speak BACnet. Let me introduce you to my stepbrother, the VFD bypass. Hello, I am a VFD bypass, and I speak BACnet, too. There is an incredible amount of information in me; all you have to do is ask. ABOUT THE AUTHOR Tim Skell is a HVAC Application Engineer for VFDs at ABB. He has more than 10 years of experience with VFDs in the HVAC market. He is also an ASHRAE member and is an active member in the BACnet community, recently winning the BACnet Howler Award.
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CASE STUDY: Ohio University By Steve Jones
Managing Partner, The S4 Group, Inc.
O
hio University, a university located on an 1,850-acre campus in Athens, Ohio in the United States, has been upgrading their building automation equipment. Their 60 buildings include BAS technologies from Siemens, JCI NAE, Andover, Tridium, Honeywell, ALC, and legacy JCI Metasys® N2.
This case study focuses on three buildings that have JCI legacy N2 in them: • The Ping Center is one of the largest recreational facilities in the country; • Baker University Center is a vibrant welcoming hub; and • The Life Science Research Facility houses Biological Sciences.
Customer Requirements 1. Continue using the existing Metasys® configuration and commissioning utilities 2. Integrate 300 Metasys® N2 VMAs into the enterprise 3. Make all VMA point values available to the global controller and air handling units 4. Include N2 Point Override support 5. Provide a long term migration path for the VMAs to current technology field equipment 6. Provide a campus wide, single seat interface 7. Avoid downtime during the integration 8. Improve energy efficiency Solution Several technical approaches were considered for these three buildings: replacing the NCMs with NAEs, using the third-party N2 driver for the JACE, or using a FieldServer device. None of these technologies met all the University requirements. The solution was to replace existing Johnson Controls NCM350 controllers with Vykon JACEs for the graphical single seat interface, global control functions, and energy management applications. An S4 Open: BACnet-N2 Router was paired with each legacy Metasys® NCM, providing the integration services between the legacy Metasys® N2 technology and the JACE via BACnet/IP. Each legacy N2 device is emulated as a virtual BACnet device under a virtual BACnet network. The N2 Router enabled the co-existence of the legacy NCM and Metasys® OWS with the JACEs thereby keeping the critical HVAC pro Passthrough support intact.
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The following diagram demonstrates the Ohio University campus-wide solution.
This project was handled by two integration companies. Limbach—www.limbachinc.com—provided the site preparation work, the purchase and installation of the S4 Open: BACnet-N2 Routers, and development custom device templates for the BACnet-N2 Router from Metasys® HVAC PRO configuration files. They used the configuration wizard in the S4 Open Management Console to finalize the integration into the legacy Metasys® systems. Following the discovery of the virtualized N2 devices as BACnet devices in the Vykon Jace®, GPL processes were migrated from the NCM into the JACE. The final step was confirmation of end-to-end data integrity. After the groundwork was laid by Limbach, Building Controls Integrators (BCI)—www.bcicontrols.com—was responsible for point alarms Annunciation and graphics for the enterprise system. Outcomes The customer was impressed with the minimal downtimes and impact on operations during the project. All project goals were met or exceeded. ABOUT THE AUTHOR Steve Jones’ career spans 43 years and includes experience in networking and telecommunications, technology, IT, government contracting and building automation. Jones founded the S4 Group in 2002 in order to address the integration opportunities within the building automation space.
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Exclusive Discount Offer for BACnet International Members There is a consensus in the industry that the proliferation of intelligent devices and internet technologies has created an exponential increase in the volume, velocity, and variety of data. This phenomenon is commonly referred to as ‘Big Data.’ Current data management systems are not capable of processing this new influx of data, and as a result companies are forced to ignore the majority of the data available. The goal of Continental Automated Buildings Association’s (CABA) Intelligent Buildings and Big Data Research Study was to examine new tools and resources that can help companies filter, analyze, and use big data collected from intelligent and integrated buildings. Leveraging big data will enable a better understanding of customer behaviors, competition, and market trends. Research on utilizing big data from building systems is crucial to staying competitive in this dynamic connected marketplace. Thanks in part to BACnet International’s sponsorship and support of CABA’s Intelligent Buildings and Big Data Research Study, members of BACnet International are being given access to the full report at a 25% discount off the full price. This makes the report available to members at the discounted price of $3,675. Don’t forget to order a copy of the full report today! To do so, simply contact BACnet International Communications and Community Manager Erin Hall at erin@bacnetinternational.org.
We Want to See You at PlugFest! October 6-8, 2015 The University of New Hampshire Durham, NH The BACnet International BACnet Testing Laboratories Working Group (BTL WG) invites manufacturers of BACnet products to attend the 16th annual Interoperability Workshop at The University of New Hampshire in Durham, NH. This event permits vendors to test their BACnet products with BACnet devices from other vendors in a neutral and friendly environment. In 2014, nearly 90 BACnet engineers representing 30 companies attended the workshop and improved their BACnet implementation and testing methods. Registration is now open! Discover PlugFest details and register today at the PlugFest website, www.bacnetinternational.org/plugfest. PlugFest Pricing • Platinum, Gold & Silver Members: $400 per attendee • Integrators & Public: $850 per attendee • Committee members are eligible for an additional discount per attendee For more information and registration details or questions contact Membership and Trade Show Manager David Nardone at david@bacnetinternational.org.
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BACnet International: Continually Raising Building Standards
Leading the World in Building Protocol Standard: BACnet plays a significant role in building automation projects worldwide. In 2015, the open communication protocol for BACnet celebrated its 20th anniversary of being ANSI standard. This follows the 10th anniversary in 2014 of BACnet being published as DIN EN ISO standard. Today, there are thousands of product models and millions of devices speaking BACnet. Improving Interoperability: BACnet International is an industry association that facilitates the successful use of the BACnet protocol in building automation and control systems through interoperability testing, educational programs and promotional activities. Achieving the Mark of Distinction: The BACnet Testing Labs (BTL) Mark provides users with assurance that a product has passed the industry standard BACnet conformance tests conducted by a recognized, independent testing organization. The BTL Mark is a mark of distinction, achieved by more than 600 products, that many building owners and control system designers look for as a must-have in order to be eligible for a project.
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DISCLAIMER OF ENDORSEMENT Foundations is a publication which is designed to be as inclusive as possible in sharing of views and information. As such, there may be references to resources, products, companies or services that have not been vetted or endorsed by BACnet International. BACnet International provides these resources solely for your information. Responsibility for accuracy lies ultimately with the individual authors.
SPECIAL THANKS Foundations is an educational resource produced by BACnet International for its members. BACnet can be a cornerstone of your building automation success and Foundations builds on that by providing a wide variety of timely and relevant articles. Additionally, Foundations is supported by the BACnet International Board of Directors: Andy McMillan, BACnet International Brad Hill, Honeywell International Roland Laird, Reliable Controls Trevor Palmer, Distech Controls Raymond Rae, Delta Controls, Inc. Nancy Stein, Siemens Industry, Inc. Michael R. Wilson, Automated Logic A special thank you to all volunteers in the BACnet International community.
COPYRIGHT © BACnet International 2015 Further editorial use of articles in Foundations is encouraged. Please send a copy to the BACnet International office at erin@bacnetinternational.org. © BACnet is a registered trademark of the American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc. (ASHRAE).
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