April 2011

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Why you need to achieve (BTL)
ACnet test laboratories (BTL) established by BACnet International is responsible for compliance and interoperability testing of BACnet products. The test lab defines test plan for each BACnet profile and conducts rigorous test case suit.

Nirosha MunasingheNirosha Munasinghe MBusIT BSc BE (Hons) (Melb)
Product Development Manager,
Open General 

Contributing Editor

It can be argued that BACnet is the dominant protocol in the building automation market.  The number of BACnet vendors has more than doubled in the last five years. As of March 2011, there were 505 BACnet vendors registered world wide.  The presence of such a large number of vendors is great for the market. It is pushing the protocol to new levels and evolving at a rapid rate. Most importantly, the growth is increasing the competitiveness of the market, offering the building owners a choice.  Having a choice is important in many aspects of life but choice implies decision making.  How do you choose a BACnet product from pool of 500 plus vendors. Of course, a simple factor in the decision making process, is the reputation of the company. The other is the monetary component in any business decision.  From a technical point of view, one of the most important factors in the checklist is if the product is BACnet Test Lab certified. This article examines what is the meaning of the  BACnet test lab certified product and the benefits to the value chain of the BAS industry.

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BACnet test laboratories (BTL) established by BACnet International is responsible for compliance and interoperability testing of BACnet products. The test lab defines test plan for each BACnet profile and conducts rigorous test case suit. Along with the European WSP lab in Germany, BTL is the only professional laboratory means of verifying if a BACnet device conforms to the standards.

One of the key strengths of the BACnet protocol is that it offers the vendors the CHOICE to implement the same feature in different methods. To the end-user the output looks the same but the operation underneath differs. For example; to trigger an alarm, the initiating device requires a destination address to send the alarm. To resolve the destination address, BACnet standard’s formal definition is:

Graphic 1

In plain English, this means that destination device can provide the alarm initiating device either the actual address of the destination OR the ID of the destination. If the actual address is given, the initiating device stores the address as the destination. If the ID is given, it is up the initiating device to use the ID to find the address of the destination device. Therefore, if the device supports alarming, it needs to support both methods for interoperability. Just like this simple example there many choices available in the BACnet standard. When a vendor begins the development process, it is very easy to implement only one choice, not both.  This is perfectly fine and will operate without any problems, if the system operates with only one vendor.  However as the system is integrated with other vendors, problems commence to surface. One vendor supports only the first choice; whereas the other vendor supports the second choice, hence causing interoperability issues. The only means of testing all these combinations is in a professional independent laboratory environment.

What does it mean when a device is BTL certified? Does this mean the device is bullet proof? No. BTL certifies the associated BACnet objects and services of the device profile. This includes the encoding and decoding of the data, the support of correct properties for each object, the support of all required fields in services, the physical communication parameters and most importantly the device’s ability to handle errors. It is important for decision makers to understand that proprietary components of BACnet devices such as accuracy of input and output (IO) readings and program execution is not tested as part of BTL testing. The protocol information conformance statement (PICS) released by BTL outlines the date, BACnet protocol revision, objects, services and mediums the device was tested under.  It is important for the decision makers to analyse the PIC statement released by BTL as opposed to PIC statements released by the manufacturer, to differentiate what is officially tested. The manufacturer will continue to add more features to their product after obtaining BTL certification and continue to update their feature list in the PIC statement. However, the decision makers need to be aware, that unless these features are listed in the BTL PIC statement it is not officially tested by BTL.

What is the process of a BACnet vendor to obtain BTL certification? It is a methodological process between the vendor and BTL. When a device has completed internal vendor testing, a functionality checklist is submitted to BTL describing the profile of the device. The functionality list contains all objects and services supported in the device. It is recommended that the vendor complete comprehensive internal testing before submission to reduce cost of testing and time. The BACnet Test Framework from MBS in Germany is an excellent pretesting tool for vendors. The tool offers full testing of each profile before submission of the device. Once the functionality list is approved, the testing of the device begins with continuous feedback from BTL in USA and India. Having personally experienced the BTL testing process on the Open General product line recently, it is highly recommended for any BACnet vendor.  Three continents were involved; Australia, USA and India but the procedural workflow process made it possible to achieve BTL listing for an advanced application profile device in less than eight weeks. It is another example that BACnet is a truly global solution. 

What are the benefits to the value chain of the building automation industry? Simple answer is compliance and reliability, which leads to greater benefits.

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The initial cost analysis of BTL certification processes for a smaller BACnet vendor can seem a costly exercise but in the long term the certification will benefit the product and the growth of the company. It is possible to have internal testing and quality assurance teams, but as most developers would agree that in most cases when a device is tested in an independent environment, they are more than likely to discover new errors. We all know the costs associated with finding errors during a project installation. It is always best to find it early, than later.  Also, most consultants are specifying that the product must be “BTL Listed” for it to participate in the tender market. Therefore, not only the testing process will give the confidence to the development team but the company will benefit intangibly.   

System Integrator

Representing a BTL listed product implies that the system integrator can confidently present its' solutions to the end user. A BTL listed product allows the system integrator to tender more projects increasing business potential. A proven product also allows the system integrator to devote more time to enhancing the value of the BAS to the client and less on troubleshooting with support enquiries to the vendor.

End User

The primary beneficiary of a BTL listed product is the end user.  A BTL listed product is not a tangible benefit to the end user when comparing to the same featured product that is not BTL listed. That is, the customer cannot see feature differences between the two products. However, benefits of proven and tested product cannot be seen or touched. The end user is choosing a product that is compliant to the standard and interoperable for the future. A stated fact of the BACnet protocol is multi-vendor integration. Installing a BTL listed product will go a long way to achieving integration and future proofing the facility.  

A BTL listed product benefits the entire value chain of the BAS industry.  The decision makers need to be aware of the intricacies when choosing a product from a pool of vendors, keeping in mind that a BTL listed product will not resolve all problems associated with controls. It is a process that certifies a device to BACnet compliance and reliability.    


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