|
Making Commercial Controls
Work
Nearly everything about a controls system—the
points, architecture, integration, etc.—comes from the requirements defined in
the sequence of operation.
|
Paul Ehrlich, Ira
Goldschmidt
& Angela Lewis
Building
Intelligence Group
As published
December Issue - Column
|
We are fortunate in that the focus of many of our projects is in making the controls
work (and surprise – a superior control system is more easily achievable when it
is the project’s main goal). However,
most building controls are installed as part of general construction projects
(e.g., a “spec” office building) in which making the controls work does not
seem to be at the top of the priority list.
Recently we provided services on a fairly typical new-construction office
building project which provided some great insight into what is needed for
making controls work in this environment.
What we found added some interesting counterpoints to our September
column “Why Is It That Control Systems Don’t Work?”
GET
ENOUGH FEE
Making
a control system work starts with getting sufficient design fee for the hours
needed to “do it right”. Without
pointing fingers, current A/E business practices for typical commercial
projects usually yields engineering fees that are not commensurate with the
design effort required (which in turn leaves little to no fee for the controls
design). If you want your control
systems to work then you first need to learn what fee is needed and then pick
and choose your projects based on the ability to meet this goal. If that fee cannot be obtained then the quality
of the control system will be mostly left to luck (or, worse still, the fee
will go into the red finishing the design through the RFI and/or commissioning processes).
Even
with a reasonable fee the amount of engineering time available for controls
design on general construction projects will still be fairly limited. Unfortunately, current A/E practice involves
many design iterations that seem to go well-beyond the traditional SD/DD/CD
phases. Interim/90% review and/or GMP design
submissions add to the effort along with the near daily battle to keep up with
the Architect’s design changes. The controls
design effort needs to practice restraint concerning when to expend the fee. The best approach is to keep design efforts
to a minimum except for the most important design phase deliverables. Better yet, leave as much of the controls design
to the latter part of the project when it is clear what the control system
needs to control in the first place (in earlier stages deliverables should
remain at a clearly delineated “outline” or even narrative level). If not, the controls design effort will just
be needlessly chasing all of the other disciplines’ design iterations.
CHOOSE
YOUR DESIGN BATTLES
Many
engineers substitute quantity for quality when developing controls design
deliverables. A typical commercial
project doesn’t need as much information as many might think. The following provides some specific guidance
on where to put your design efforts:
- The sequence is of the greatest importance. Nearly everything about a controls system—the
points, architecture, integration, etc.—comes from the requirements defined in
the sequence of operation.
- A point list is useful but don’t
over-embellish it. Are large complicated
tables (with columns for “trends”, “setpoint”, “alarm”, etc.) really worth the
effort especially if points are already shown on the drawings?
- Are control drawings really necessary? Does a control drawing for a VAV AHU or box
add any useful information?
- Keep the controls specification simple. Once the allowable manufacturers are listed
in the specification then 90% of the system products/design becomes fixed. Use the specification for the 10% you can influence
like the few field devices that involve real quality/cost choices (e.g., flow
meters), some installation issues (e.g., where should IP controllers be used, who
provides the IP communications…), etc.
- Don’t forget some key integration issues! A little time spent on reviewing/editing all of
the other specification sections for equipment to be integrated (i.e., to specify
the protocol to be used and the communicated data) will save huge amounts of
time during construction.
THE
CONTRACTOR DOES THE CONSTRUCTING NOT THE ENGINEER, BUT…
You
might be able to guess where we’re going with this but it will have to wait for
another column.
About the Authors
Paul
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
directly at
Paul@buildingintelligencegroup.com or
ira@buildingintelligencegroup.com
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