Sunday, July 28, 2019

Procure BACnet System

Procure BACnet System

BACnet was designed to allow communication of building automation and controlsystems for applications such as heating, ventilating, and air-conditioning control (HVAC), lighting control, access control, and fire detection systems and their associated equipment.
The UDP port number 47808 (in hexadecimal, X'BAC0') identifies BACnet messages and is the UDP port used by PAD devices. BACnet/IP devices use this UDP port by default but may be configured to use a different number if necessary. An open protocol should be powerful and robust, capable of meeting all future communication needs, as well as the present needs throughout all system levels. Any communication protocol which doesn't meet these criteria should be eliminated from further consideration.

BACnet's open structure and object-oriented commands enables developers to provide enhancements or features, while still maintaining full interoperability for all core operations. If use of a new control feature becomes widespread and there is a need for it to be standardized among vendors. ASHRAE provides a procedure for it to be adopted as a standard BACnet object or service.
BACnet is a widely accepted, non-proprietary open protocol standard. Companies began announcing their support for BACnet even before the final draft of the standard was released. The fact that ASHRAE developed BACnet plays a significant role in this acceptance. ANSI perceived BACnet to be a significant development and adopted it as a protocol standard within months of acceptance by ASHRAE.
Components vs Systems
For many years the BACnet community has worked hard to ensure that BACnet is a global standard and that it’s implemented consistently across multiple supplier product lines.  BACnet International devotes substantial resources to the BACnet Testing Lab (BTL) and to annual device “plugfests” to support that objective.  We regularly point out that BACnet is a global consensus standard and we trumpet the value of standards.  We talk about component interoperability and in some cases even interchangeability.  All of this is good.  Users need to understand the power of standards and how specifying systems that incorporate BACnet can add value to their building automation investments.  However, by promoting BACnet as standard and then using the shortcut term “BACnet System” we invite the unschooled to mistakenly extend the concept of “standard” from the communications protocol to the system.  That seems to lead some of them to the conclusion that all “BACnet Systems” are essentially equivalent and can be procured like commodity products … even to the point of the “reverse auction” procurement process for an energy management system I recently encountered. 

Reverse Auction Procurement
Reverse auctions have been around for more than a decade.  They evolved as a “simple” way for buyers to drive down the cost of components.  The essence of reverse auctions is that suppliers bid back and forth for a well-defined piece of business on the basis of price.  Full-featured web platforms have evolved to support this purchasing model but, even so, it has its limitations.  One of the biggest limitations is that for it to be effective, the product and its associated transaction attributes (e.g. lead time, delivery date, etc.) need to be unambiguously defined in terms that can be readily measured.  And therein is the rub.  Energy management and building automation systems are complex so fully defining all of the important attributes is a huge challenge.  Leaving any important attribute undefined results in suppliers compromising on those unspecified attributes to achieve the lowest cost and win the business.  On the surface the result might look like a good deal for the buyer.  But those compromises might well come back to haunt the buyer in the long run.


Lessons Learned
It was an attempt to give people new to the BACnet community some insights based on the experience of people who have already designed and operated systems built around BACnet.  One of those “lessons learned” was that a “BACnet System” is still a system. The BACnet standard can make system integration faster, simpler and more effective but it is not a substitute for system expertise, creativity or design rigor.  Nor does BACnet provide any assurance of product quality or system effectiveness.  These come only through knowledge and experience.  So, I encouraged owner/operators to develop a partnership approach to working with suppliers who have that knowledge and experience. I saw first-hand what happens when complex systems procurement is driven from a “first cost” perspective without sufficient focus on supplier partnerships.

Benefits of BACnet Protocol

  • Single operator workstation for all systems
  • competitive system expansion.
  • Eliminates fear of being an owner to be locked in with a single vendor.
  • Possibility of integrating all BAC Functions.
  • Interoperability
·         Data sharing
·         Alarm and event management
·         Trending
·         Scheduling

·         Remote device and network management

Summary
BACnet is a standard. All the necessary elements are in place: strong customer demand, a robust open standard and manufacturer's support of the standard. BACnet seems to provide a complete solution to interoperability issues for building procurement  team.  Understanding the difference is important in establishing a procurement process that builds positive supplier relationships and generates maximum value in acquiring an energy management or building automation system. SSA Integrate can guide how to utilize this.


9 comments:

Jarod Couch said...

Has anybody ran a bacnet network or lon cable? Is it possible? How bad were the nightmares? EDIT: Let me specify, this is not my choice, I was thrown into this job midway.

Kenny Cochrane said...

There are multiple references available with a simple Google search. Typically you should run LonWorks on Level 4, 22/2UTP or TSP and BACnet on an RS485 compliant cable like a 22/2TSP low cap. All this other crap is a great way to lose money.

Jeff Houpt said...

Lon requires special wire certified by echelon, it'll be stamped on the wire. Bacnet requires bacnet wire also stamped. Lon will also require a EOL (end of line resistor). The resistor size is dependent on the gauge of wire you ran. Length is also a factor. I have a cut sheet for lontlalk requirements if you want it let me know. I'm not aware of any EOL needed for bacnet.

Robert Horton said...

I have a question. I'm being asked by one of the people that are with the fire system company, how to shut down an RTU from their FACP. The RTU has a BAC-8304-56 installed on it. On the documentation for the BAC-8304-56, it shows where it can be wired for emergency shutdown.

I'm still new to all this and I'm slightly confused. Does a signal just need applied at the input and that will close the contact OR does the controller need wired to a normally open contact, that when it closes it completes the circuit and shuts the fan down? Let me know if you need any other info. Any advice is appreciated. Thanks!

Ryan McAndrews said...

Fire alarm in my area is always normally closed contacts on a relay provided by FA contractor. When they open contacts on their relay, it kills power to my safety circuit relay and hardwire shuts off fans and closes dampers.

but I want to call attention to the fact that two different solutions have been offered thus far ... a) shutdown, or b) smoke control. These options will require different solutions. Shutdown should stop the fans & close dampers. True smoke control is a little more challenging - typically, the “fire zone” goes to “exhaust mode” (closing OAD & MAD) causing the fire zone to go negative pressure with respect to adjacent zones, while adjacent units go to “vent” mode, bringing in fresh air and causing those areas to positive pressure with respect to the fire zone (smoke can’t “swim upstream”). Also, you need to know what the AHJ wants, preferably, backed up with a specific code requirement OR if it is part of your contract docs to provide the link. If the requirement isn’t there, you should consider a change order ... I don’t imagine that you’re in the practice of giving away work. ��

Venba deepi said...

Very Nice. This blog is very useful to me. Now I have clarified my doubts on ISO 50001 Certification .

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