Resources for the Resourceful; Control Point Naming Conventions

In my previous discussion regarding the controls
integration meeting
concept, I mentioned that one of the topics
for discussion in the meeting should be point naming
conventions.

Point names and descriptions are critical in terms of allowing
the folks involved with operating the building to quickly interpret
what is going on and respond appropriately.  Most control
systems come with default point names and descriptors, which, while
better than nothing, can leave a lot to be desired.  This is
especially true for systems where points are objects in a file that
is unique to a specific controller rather than unique objects in
and of themselves.  In situations like this, you can end up
with hundreds of points with the same factory default name and an
all points log of the zone temperatures may look something like the
following:

….
250 SPACE TEMP ANALOG
INPUT                
75.2 F
251 SPACE TEMP ANALOG
INPUT                
74.8 F
252 SPACE TEMP ANALOG
INPUT                
73.6 F
254 SPACE TEMP ANALOG
INPUT                
75.2 F
255 SPACE TEMP ANALOG
INPUT                
74.2 F
256 SPACE TEMP ANALOG
INPUT                
76.2 F
257 SPACE TEMP ANALOG
INPUT                
72.6 F
258 SPACE TEMP ANALOG
INPUT                
76.1 F
259 SPACE TEMP ANALOG
INPUT                
73.7 F
….

The obvious question, of course, is which space temperature is
being referenced by, say point 254 out of the 756 space temperature
points on a large high rise.  This question becomes more
pressing when the alarm printer kicks out a warning like this;

HIGH TEMP
ALARM  SPACE TEMP ANALOG
INPUT                
79.2 F

Something along the lines of the following might be a bit more
helpful in terms of allowing a timely response to a potentially
important (at least in terms of your career path) problem.

HIGH TEMP
ALARM  CEO’s Office Zone
Temperature           79.2
F

If I’ve tweaked your interest in this topic, Ken Gillespie of
Pacific Gas and Electric presented a paper titled A
Guide for Specifying Performance Monitoring Systems in Commercial
and Institutional Buildings
at the 14th
National Conference on
Building Commissioning
.  In addition to recommendations
regarding point requirements for performance monitoring, the guide
that is the focus of Ken’s paper includes a point naming
convention which you could adopt as a standard or as a starting
point for a standard.  The actual guide can be downloaded by
visiting LBNL’s
Continuous Performance Monitoring Systems
website pictured
below.

The reason point naming conventions are an important topic for
discussion during the controls
integration meeting
is that accommodating your preferences
regarding point names early in the control design process is a
relatively easy thing.  Most control technicians that I know
would say that they are happy to name the points in your system any
way you would like them to be named;  they just want to have
to do it once. 

This is because if the point data base and programming have not
been generated, then the control technicians simply need to reflect
your preferences in the point data base and software as they
generate it.  But, if they have already done the work, then
accommodating your changes will require that:

They go back and revisit all of the
points
that you want to rename.

They review all of the software and
find all of those old point names and change them to the new
names.

They review all of the trend
definitions
and find all of those old point names and
change them to the new names.

They commission and debug the software
to fix errors that were introduced by inadvertent typos as they
went through and made the changes.

So, while you may find it annoying to receive a change order
reflecting a significant cost to accommodate your seemingly simple
punch list (i.e. end of project) item requiring the control
contractor to make a few changes to the point names and descriptors
on your project, its probably legitimate, at least in
concept. 

Taking some time to define your requirements in the the project
specifications and point list
and then discussing those
requirements with the control system team early in the construction
phase via the controls integration meeting process can  go a
long way toward avoiding such a change order and the related
heartburn at the end of the job.  And, its a great way to get
the Owner and their operating team involved in the process to boot!

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