Forward (condensed from Practical Controls)

The title of this book, Practical Controls, sets the tone and style of the text
within. The approach that it takes is one of practicality. To that end, the author
attempts to describe the content in terms of “real world” practices and
principles. The subject matter is purposefully short on theory, and often long on
reality. The concepts covered in the following chapters stem from the practical
experience gained by the author as an employee of a mechanical contracting
company, one of which maintained control systems design, installation, and
commissioning capabilities. The book’s intent is to try to convey the practical
methods of control as learned by the author throughout his years as a control
systems designer working for a mechanical contractor. Although written from a
mechanical contracting perspective, the book hopefully appeals to all corners
of the HVAC industry, from consulting engineers to controls contractors.

Here is the place to define a suitable candidate for this book, what they should
know going into it, and what they can expect to get out of it. This is not
intended to be an introductory to the HVAC field of study. It is intended to be
read by a second-year HVAC student, or someone with at least some
experience in the industry, perhaps knowing a little bit about most of the
topics. The content herein assumes that the reader has a requisite knowledge
of HVAC in general, of the fundamental concepts of mechanical systems and
design, and at least an idea of how mechanical systems should operate. The
content also assumes a prerequisite familiarity with the basics of electricity by
the reader. The book expands on these presumptions, with the intentions of
giving the reader a “nuts and bolts” explanation of the fundamental concepts of
control. It will not make a control systems designer of the reader. However, it
will give both students and experienced HVAC professionals a well-rounded
education on the practical methods of HVAC control.

The topic of controls in general is large and continually evolving. Whereas
many of the basic design concepts of mechanical systems have been
solidified generations ago, control system design seems to be ever-changing,
in terms of what technological advances have to offer. The means to control
these mechanical systems is in a state of continuous evolution, insofar as to
what we have at our disposal in terms of tools and techniques. The basic
concepts of control may be well established, but the means and methods are
constantly changing, driven mainly by technology and ingenuity.

There is no possible way to cover every aspect of this broad subject in one
single edition. To focus upon the intention of this writing, the author has taken
the liberty of omitting certain topics that fall under the general subject of
controls as they apply to the HVAC industry. Classical controls and control
systems, such as pneumatics and electro-mechanical sequencing controls,
are not covered herein, even though they are still in wide use even in this day
and age. The material presented in this book deals strictly with electrical,
electronic, and microprocessor-based controls and control systems. Also
excluded for the most part are any detailed discussions on the internal controls
of packaged equipment. Items such as packaged rooftop units, boilers, and
self-contained chillers have most (if not all) of their controls components factory
installed and wired, thus providing for a complete, factory furnished control
system. Though in places the author will touch upon factory equipment
controls, the material mainly focuses on those types of equipment and systems
that must be fitted with engineered control systems.

The direction that this book takes, is that of laying down the basics, and
building upon them. This is found to be true as the reader journeys from
chapter to chapter. It is even more so the case within the chapters themselves,
with each section of a chapter building upon the previous section. It is
important that the reader start each chapter from the beginning, and read and
comprehend each section before moving on to the next. Once read and
understood, this book can from then on serve as a “reference manual” for the
reader, perhaps to be utilized as a design tool and/or as a practical resource.

In attempting to succeed in the goal of this book, the author periodically
provides insight into how mechanical systems are designed, and how they are
designed to operate. Stopping short of full-blown discussions and descriptions
of mechanical design concepts, the author will include enough on a given topic
to illustrate not only how the particular equipment and system is controlled, but
also why it’s controlled the way it is.

The topic of controls and control systems in HVAC is an extensive one. By no
means will this book cover all aspects of the topic, nor will it cover any single
aspect to any great extent. However, it will delve into and discuss a broad
array of different concepts falling under the general topic, and will thus serve
as a good foundation to a further education in controls, should the reader
choose to pursue it…

Practical Controls Book Excerpts