Succesful Building Automation
6 Things you MUST know
By Robert Benson PE, CxA
Director of Engineering
Building automation is an effective tool to centralize useful building systems data,
which can help reduce costs, both operational and capital. To obtain these savings,
your building’s systems need to be able to communicate with one another. Achieving
that kind of integration requires specialized knowledge and planning from a specialist
with the rare combination of engineering knowledge and hands-on field experience.
Building Automation Systems (BAS) regulate and manage multiple building functions
such as HVAC and lighting, allowing you to identify and diagnose operational issues
early on and preventing costly breakdowns that interrupt business operations.
BAS can also help you save between 5 and 30 percent on building energy costs.
To enable your building’s various systems – produced by different manufacturers –
to talk to each other, the Architecture, Engineering and Construction (AEC) industry
established Building Automation and Control Networks (BACnet), a data
communication protocol standard.
But even the best systems and tools need to be used effectively to maximize results.
At DCM Energy, we regularly encounter situations where BACnet integration is not
performing optimally, resulting in intermittent inter-system communications, inability
to perform expected functions, or worst case scenario, a total lack of communication
between building systems. When DCM performs commissioning for our clients, we
flag potential issues for early correction – during pre-planning, pre-design and/or
specification – saving our clients from downtime and costly change orders.
Successfully integrating complex systems requires an informed, integrated approach
and clear communication between owner, design engineers, field technicians, and
manufacturers. Involving an expert Commissioning Agent early on in the design
process can help ensure your building’s systems successfully communicate with each
other consistently; enabling you to reap the full benefits of building automation.
Here’s how to avoid the most common problems with that we’ve
encountered on commissioning and retro-commissioning projects:
1. Select BTL-listed Devices
Start with what’s been proven to work. No matter what a manufacturer claims, if a
product has not been successfully tested and listed by a BACnet Testing Laboratory
(BTL), there is no way to know whether it will correctly integrate. Utilizing non-listed
devices all too often leads to a communications dead end for both the BAS and
You can see whether a device is BTL listed at www.bacnetinternational.net/btl/.
2. Ensure BBMD Compatibility
Check for broadcast capability. The BACnet/IP Broadcast Management Device
(BBMD) enables BACnet devices to operate as a system across a wide network.
It is critical to learn during the design phase whether specified devices and
equipment support BBMD so that the DDC contractor knows to furnish and install
the appropriate gateway to achieve the desired functionality. Missing this step can
result in costly change orders down the road.
3. Enable Proprietary Services & Objects
Ensure field implementation. While BACnet is an “open protocol,” certain services
and objects within a manufacturer’s device are allowed to be proprietary. If desirable
functions are “hidden” within proprietary services and objects, another manufacturer,
including the controls firm, cannot turn on these functions in the field. If proprietary
services or objects are allowed, the specification should call for submittal of these
proprietary items so that another party can enable complete system integration to
4. Identify Exact Points to be Mapped
Be precise. Even when dealing with BTL-listed products, you need to rigorously
define the sequences to support basic desired functions. During the specification
process, it is imperative that the engineer identify the exact points to be mapped via
BACnet – from the field device to the front end, and to specify the functionality of
those points – e.g., read vs. read/write.
5. Ensure Specifications Comply with Equipment
Be realistic. Engineering design must respect the limitations of available products.
If a ductless mini-split system does not allow changing set points and schedules via
BACnet from the front end, then you cannot specify that requirement. No matter how
elegant the engineer’s design, manufacturers can only be asked to provide
functionality that is within their products’ capacity.
6. Unit-furnished vs Field-mounted Controls
Understand the costs – in dollars and hours – of your selections. There are costs
associated with integrating equipment controls via BACnet (unit furnished) versus
having the DDC contractor furnish his own field mounted. While it is cheaper to install
and wire unit-furnished controls, their field coordination is more time consuming.
Some unit-furnished controllers are not freely programmable, and any changes
beyond what was initially specified require two separate software changes: one by
the field technician for the unit; and one by the field technician integrating the points
to the front end. When this happens, you’ll usually end up paying two companies:
the unit manufacturer who changes the program; and the BMS company who adds
the new points to the front-end graphics.
In summary, the key to successful building automation is engaging a specialist with
knowledge and planning expertise in both engineering and commissioning field
operations. DCM is that specialist and we are happy to assist you in making your
building(s) operate efficiently and effectively.
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