Networked Building Automation System (BAS)
It is amazing how little we know
what really goes on in most buildings.
Paul Ehrlich, Ira Goldschmidt
& Angela Lewis
November Issue - Column
It is amazing how little we know about
what really goes on in most buildings.
While much of what happens is none of our business, we are
about how key building systems are operating.
One of the greatest advantages of using a networked building
system (BAS) is that we should be able to gain valuable insight into
operations. Unfortunately, what we often see is only a glimpse, an
at a point in time that may not represent what is actually happening
of the time. There are several valuable
tools we would recommend for gaining better understanding into the
Almost all BAS installations provide
the ability to trend system variables.
Trends (or trend logs) are typically configurable, and can be
set up to
occur at a fixed interval, or upon a change of value or state. While some systems come with a limited amount
of trending automatically enabled, most require the operator or
contractor to set up the trends.
Defining a trend is a task that should be fairly easily
operators should receive instruction on doing this during training. Despite being a very valuable tool, we find
many systems where this function is rarely used. Why? --
There are several problems with BAS trends.
The largest problem is that the process to set them up is
generally not user
friendly; users need to set them up in anticipation of problems,
limited capacity to store trend data and the tools available to view
trend data are fairly limited. Most
systems provide the ability to view trend data, but to do in depth
typically requires exporting the data and analyzing it with a tool such
Microsoft Excel. The process of data
export can be tedious, and properly using spreadsheets requires skill
training. In short, we find that trends are a valuable, but often
Another alternative for collecting
building system trend data is the portable data logger.
These devices are inexpensive, robust and
versatile. The ones we are use cost
around $100, come with built in temperature, humidity and light sensors
collect 43,000 data samples. They are
easy to set up and deploy and do a reliable job of collecting
information. When we are evaluating
buildings that don’t
have a current BAS installed the use of data loggers is the way to go. Data loggers are also be an excellent means
for validating and commissioning BAS.
Deploying a logger allows for ready measurement of values, both
providing verification as well as often being easier to set up and
trend logs. Of course, the task of
analyzing the data typically comes back to the use of a spreadsheet.
good Excel skills are invaluable!
The goal of data collection through
trends and loggers is to analyze how well the building is working over
temperature control stable? Are systems
shutting off at night? Is the economizer
really working? The challenge is to use
this information to close the gap between a functioning building and
is optimized. By collecting and
analyzing this data over time we can start to analyze proper operations
move toward high performance operations.
Sample data log
of system during
About the Authors
and Ira first worked together on a series of ASHRAE projects including the
BACnet committee and Guideline 13 – Specifying DDC Controls. The formation of
Building Intelligence Group provided them the ability to work together
professionally providing assistance to owners with the planning, design and
development of Intelligent Building Systems. Building Intelligence Group
provides services for clients worldwide including leading Universities,
Corporations, and Developers. More information can be found at
www.buildingintelligencegroup.com We also invite you to contact us
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