Building Automation: Commissioning An Intelligent Building
Given the multiple systems involved, intelligent building technology presents a unique design and construction challenge, some of which might be at the enterprise level and provided by the owner. This makes it a great candidate for the ever-expanding role of the building commissioning agent. But is this industry prepared for the types of testing involved with intelligent buildings?
To us, the answer to this is to be found in the commissioning industry’s track record with the current breed of BAS that involve controls from various sources (those provided with the chiller and CRAC units, factory-mounted AHU or VAV box controls, etc.). In these buildings, the standard set of commissioning tests may not be sufficient. The reason is that interoperable communications between different manufacturer’s products using BACnet®, LonMark®, etc. is a key to the success of the system. Standard functional testing may not reveal whether interoperability is being fully achieved or only being achieved in the subset of tests being performed.
PUT IT TO THE TESTSo what is needed to truly test for interoperability? Some might say that a BTL listing or LonMark certification is sufficient; however, our experience would prove otherwise. These seals of interoperability approval merely provide an assurance that the product meets the testing/certifying agency’s definition of protocol functionality, not necessarily interoperability. It does not mean that the product will work as successfully in a real-world test with a group of its peer products.
In fact, we have found that these real-world environments reveal differences in protocol implementation between products such that unexpected results can occur, some of which can result in a loss of interoperability in support of the key system functions.
This does not mean that BTL or LonMark are not doing their jobs. These groups are providing a valuable service in testing and certifying protocol compliance; however, it doesn’t replace the real-world testing of products in a variety of multi-manufacturer situations.
For now, however, an additional step in the commissioning of BAS (and by extension, intelligent buildings) is very important. We would call this interoperability testing, which involves a series of tests of the protocol functions to be used in the project (these protocol functions should be those involved in the actual system functions expected along with a variety of others that might be needed). Armed with a protocol analyzer, these tests would then carefully examine the protocol service and data message packet formations involved.
These tests will reveal many interesting subtleties about how the products are truly implementing the protocols involved. For example, successful communications between two products may actually involve incorrect usage of the protocol by both products. This can be a problem if one of the products’ firmware is updated to fix the problem - all of a sudden this successful communication may no longer occur.
ONE MORE PLACEOne possibility to also consider is the use of a protocol analyzer during functional testing. This could allow a review of the communications services and data packet formations involved in the building’s most important functions to ensure that the protocol is being properly implemented. The added value of this approach is that, should a functional test appear to fail due to the communications, the information needed to possibly analyze the problem will be at hand.
Interoperability testing is an important key to the success of multi-manufacturer BAS and will become even more important to the success of intelligent buildings. ES