The Hartman Company Newsletter
Issue: March 2006
Topic: Spring Cleaning
Dear Hartman Company Newsletter subscriber,
Spring is here and with it comes spring cleaning. This year let’s not stop
when we’ve discarded outdated household goods, but let’s also bring that same
rigor to the technologies we practice in our work. For some time now it’s
become clear that our industry’s failure to divest itself of outdated control
technologies is a direct cause of the stagnation that has settled upon the
energy and comfort performance of modern buildings. Facing this reality is
increasingly important in light of the new US Federal Energy Legislation that
provides large tax credits for commercial building projects when they exceed
the ASHRAE 90.1-2001 standards by 50% or more.
Fifty percent or better than ASHRAE 90.1-2001 is not at all difficult to
achieve. Virtually every commercial building can do it cost effectively, but the
caveat is that substantial change in design and operating technologies is
necessary to do it effectively. Among the most substantial barriers to improving
HVAC energy efficiency is the continued use of PID (Proportional, Integral, and
Derivative) control loops to operate HVAC systems.
PID control leads to inefficient operation by its focus on individual component
control. New control theory demonstrates clearly that a much more unified control
approach is necessary to effectively coordinate today’s multi-component systems
so that they operate at optimum energy performance levels. Furthermore, designing
system configurations in anticipation of PID control embeds inefficiency with the
rules employed for selecting valves, dampers and in configuring decoupled
components. These standard practices lead to unnecessary pressure loses, unneeded
flow and mixing, all of which translate directly to wasted energy.
The Hartman Company has for nearly two decades been working with new control
theory and practical strategies that replace primitive PID control with what is
now called Relational Control. Relational control employs the network capacity of
modern building control systems to better unify the operation of HVAC systems for
vastly improved energy performance and at the same time improved capacity of these
systems to meet their ultimate goal - comfort for building occupants.
So here it is spring at last. Time to discard the old outdated furnishings we no
longer need. From a technology standpoint PID control is one of those outdated
furnishings. If we want a brighter, more efficient year ahead. It’s time also to
consider replacing the control technologies we use in our professional lives. Here
are some guides to help you in your efforts when you’re ready to begin:
1. You can get a general overview of relational control from an article Mr. Hartman
wrote on the subject for last October’s issue of HPAC Magazine. This article is
available at:
http://www.hartmanco.com/pdf/a47.pdf
2. The cornerstone of the development of relational control is the Equal Marginal
Performance Principle. Everyone in the industry should develop a basic understanding
of this principle. An interview with Mr. Hartman in which he outlines the value of the
Equal Marginal Performance Principle and provides further references for information
about it is available at:
http://www.automatedbuildings.com/news/jul05/interviews/hartman.htm
3. The Equal Marginal Performance Principle led to the development of the first type
of relational control, Demand Based Control. Because Demand Based Control does not
employ temperature or pressure setpoint control, it is usually much easier to setup
and rarely requires the type of loop tuning associated with PID control. It is the
relational control type that is employed to operate systems composed of multiple
power consuming components. You can learn more about the Equal Marginal Performance
Principle and Demand Based Control from an on-line article Mr. Hartman wrote on Demand
Based Control for Automatedbuildlings.com. This article is available at:
http://www.automatedbuildings.com/news/may02/articles/hrtmn/hrtmn.htm
4. For valve, pump and fan control applications, Hartman has developed a network
enabled relational control replacement for PID control based on the iterative problem
solving techniques used for many years. “Intelligent Iterative Control (IIC) can be a
useful “drop-in” replacement for PID control loops when non-linear responding loops
need precise control. It also fits very well into new techniques that don’t involve
a setpoint control. Tom Hartman explains IIC in a three part series that appear in
HPAC Magazine and is available as follows:
Part 1: http://hartmanco.com/pdf/a40.pdf
Part 2: http://hartmanco.com/pdf/a41.pdf
Part 3: http://hartmanco.com/pdf/a42.pdf
By replacing primitive PID with up-to-date relational control techniques as
described in these articles, building operation can be made much more energy
efficient and able to capture the new Federal incentives with relative ease. So,
consider expanding spring cleaning efforts this year. It will be worth the effort!
If you have questions, suggestions or comments regarding this topic, please do not
hesitate to contact The Hartman Company.
Please use "March 2006 Newsletter" as the subject of your email.
If you have suggestions for a topic you would like to see covered in a future
newsletter please contact The Hartman Company.
To search the Hartman Resource Library yourself for additional articles on this topic,
go to:
http://www.hartmanco.com/cgi-bin/dbman/db.cgi?db=resource&uid=default&view_search=1
Linda Stinnett, Editor
THC News
The Hartman Company
THC News
Copyright 2006
All Rights Reserved
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The Hartman Company
An HVAC Technology Development Firm
http://www.hartmanco.com
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