IAQ, High Performance and the Whole Halon Story The article "HVAC: The Next Generation" (CSE 01/03 p. 38) was outstanding. Well written with good supporting figures and background material. Most similar journal articles are hogwash. Thanks for sparking my day! Paul Hammarstedt, Supervisory Mechanical Engineer , The Austin Company , Cleveland Hitting the Mark I read "Sky's the Limit" by Mark...
IAQ, High Performance and the Whole Halon Story
The article "HVAC: The Next Generation" (CSE 01/03 p. 38) was outstanding. Well written with good supporting figures and background material. Most similar journal articles are hogwash. Thanks for sparking my day!
Paul Hammarstedt, Supervisory Mechanical Engineer , The Austin Company , Cleveland
Hitting the Mark
I read "Sky's the Limit" by Mark Lentz (CSE 01/03 p. 32 ) with great interest. I have done classroom HVAC design using total energy heat exchangers for sensible and latent cooling and sensible heat recovery by decoupling the outdoor air delivery from the space conditioning system. Our climate in southern Florida requires 12-month cooling and dehumidification—with a few exceptions—and the opportunity for savings from energy recovery are huge. The generally accepted HVAC system in southern Florida is VAV with terminal reheat. Unit ventilator designs have been tried in the last 20 years with disastrous and expensive results.
I'd like to see more on regenerative dual-duct systems. I am especially interested in the first-cost economics.
It's also appropriate that the article appeared in the same issue as Dr. Stanley Mumma's article "HVAC: The Next Generation" (p. 38). Dr. Mumma has been promoting this concept for several years and has now been able to examine a case study of the design. I found it especially interesting that the system is able to maintain comfortable winter indoor temperatures at outdoor design conditions without the installation of any supplemental heat. Of course, the classroom in which the design was tested is a 24/7 operation, but the recovery of this low grade energy is impressive.
Jeff Holtz, P.E., North Palm Beach, Fla.
Mark Lentz responds and adds some clarifications and credits:
The purpose of the article was to illustrate that it is possible to cost effectively construct high performance HVAC systems for educational facilities that meet or exceed current expectations for energy conservation, indoor air quality and low noise teaching environments using currently available technologies.
I wish to credit the parties I neglected to note in the story that either helped provide real-world data or made these projects possible:
W. J. Johannes, Architects, Rockford, Ill., the architect for the Old River Road School (recently renamed Stephen Mack Middle School) in Rockton, lll.
The Prisco Group of Hopewell, N.J., the architect for the Howell Township schools (who also provided the rendering that opens the article). The DOE-2 energy analysis (p. 33 and 34) that was generated for these facilities was prepared by the independent systems analysts Wood, Byk and Associates, Inc., Kennett Square, Pa. These facilities are currently under construction and are anticipated to be completed in time for the beginning of the 2003-2004 school year.
Wakely Associates, Inc., Mt. Pleasant, Mich., the architect for Harper Creek High School. This facility is currently under construction and is expected to be ready for occupancy by the 2004-2005 school year.
To Mr. Holtz' question: A common feature of all projects cited in the article is the use of a proprietary system design developed by Lentz Engineering Associates, Inc. (LEA), called the Regenerative Double-Duct System. Other new system types have been used for unique applications, like pool ventilation. There are a number of other sites which were not listed where high-performance systems have also been employed. All of these facilities deserve follow-up articles, and time permitting, these will be prepared. Also, through this and other publications, LEA plans to describe the underlying fundamentals to help the industry elevate its practices to the level necessary to begin to effectively develop and employ high-performance strategies. HVAC engineering is currently an underdeveloped science with enormous room for improvement.
Space constraints limited the breadth of detail that I could present to describe system schemes. LEA plans to eventually make this process available to the HVAC community, but it will do so only after a sufficient number of successful applications have been constructed to prevent under-qualified designers from destroying market acceptance with the inevitable design failures.
The regenerative double-duct system is a high-risk, high-benefit design which requires very high levels of engineering skill and a detailed understanding of the processes and techniques employed, and should only then be attempted with the very greatest care and caution. It is not the product of recycled ideas or "just another system," but a whole new paradigm. True high-performance design is a completely different ball game.
Every classical HVAC system is riddled with systemic inefficiencies: thermodynamic bias, failure to close the loop on latent energy, excessive dependence on and use of refrigeration, failure to efficiently process and manage the use of ventilation, the mere use of terminal reheat, failure to make effective use of low grade energy assets and high system parasitic losses being the most common. Many of these deficiencies simply cannot be corrected with classical systems. The regenerative double-duct system was specifically conceived to address all of these deficiencies. Readers should note that the vaunted geo-thermal heat pump system does not solve many of these problems and would not qualify as a high performance system as defined in this article. Furthermore, the results from the independently prepared DOE-2 analysis shows that the technology turned out to be the most costly system to both feed and maintain.
Like it or not, the HVAC industry has enjoyed a very poor track record of applying new concepts, even when they are only evolutionary developments to existing strategies. The principles of high-performance design will force engineers to develop new solutions for almost every project and employ design methods and processes that are very different from the classical HVAC systems they are used to applying. High performance design takes most designers into technological territories that are completely new to them, and the nature of the challenges they will face will require a return to fundamental practices instead of merely repeating the last project they worked on. This alone will significantly raise the bar with respect to the level of skill required for high performance HVAC system designers, but it can be done.
To protect this strategy from misapplication, the name "Regenerative Double-Duct System" has been trademarked, and patent protection is being pursued on numerous items to prevent other design firms from copying or representing their work by that system name.
While the regenerative double-duct system is physically simple and relatively inexpensive to construct, it is an extremely difficult and sophisticated system to design. The strategy was developed from a set of design objectives and principles fundamentally different from what the industry is used to and employs advanced engineering techniques and processes that are going to be counter-intuitive to the typical practicing designer. It is configured to create and take advantage of a synergistic interdependence of each system element on every other. This is especially true for this system strategy where over-design—the over-use of safety factors—so compromises system performance that it becomes the single most grievous error that can be made. Over-design not only compromises construction costs and negates efficiency advantages, but can actually destroy the system. It is literally impossible to design without a strong command of both the applicable engineering fundamentals and the specific process dynamics. The absence of this results in a very difficult and deceptively complex engineering challenge, which reduces the likelihood of success in application for most designers and design firms to virtually zero.
The learning curve for this process is long and arduous, currently taking two to three years with close supervision. Design firms wanting to use this scheme should plan on taking six to eight years to develop the skills and design techniques required before they even attempt an application. Not only will special training be required to apply the techniques used in these facilities, but so will a virtually complete technical re-education.
Mark S. Lentz, PE, President, Lentz Engineering Associates, Inc. Sheboygan Falls, Wis.
Clarifying Clean Agents' Not the Whole Halon Replacement Story
There is no single "halon." This term has frequently been used to refer to all halons. This is misleading, because historically there were two separate and distinct application sectors: total flooding, or "systems" and streaming or portable extinguishers. There are also two separate and distinct chemicals—halons 1301 and 1211. The former is a gas at room temperature and was used almost exclusively as a total flooding agent in computer rooms, aircraft cargo bays, engine nacelles and other areas where it was discharged as a gas to flood a space to a predetermined concentration (normally 5%). Halon 1211, however, has a higher boiling point and more of a liquid consistency and was used as a very effective agent as a streamer in portable fire extinguishers, from which it comes out as a rapidly evaporating liquid. Therefore, we are talking about two distinct halon chemicals, not a monolithic "halon." Further, there are references to NFPA 2001, Clean Agent Systems, but no reference to the just-as-important standard NFPA 10, Portable Extinguishers, that is the bible for clean-agent portable extinguishers.
I also disagree with Reed Varley, that two halon alternatives lead in market popularity—FM-200 and Inergen. Varley was actually describing the situation with halon 1301 alternatives, not all alternatives. FM-200 and Inergen are not at all effective as halon 1211 alternatives.
In another instance, 3M's Paul Rivers makes a rather curious comment. "No single alternative has been able to meet the same overall performance as halon for both total flooding and streaming." Again, halon is represented to be a monolithic chemical. Although it might be nice if one chemical replaced halons 1211 and 1301, there was never one agent for both total flooding and streaming.
Mr. Rivers makes the statement on p. 21, "The transition to alternative means of clean-agent fire protection has reportedly gone quite well, with the introduction of inert gas fire-protection systems and hydrofluorocarbons (HFCs) as interim solutions." This ignores the prominent role that our product, based on an HCFC with negligible environmental impact, has had as the primary halon 1211 replacement in the United States. On p. 22, Mr. Rivers states, "…all HCFCs and HFCs have one common problem: They have an environmental profile that makes them non-sustainable. The industry has come to terms with the increased cost for these alternatives, but now, OEMs, end users and specifiers are becoming concerned they can no longer make the long-term commitment to the use of these non-sustainable solutions considering their overall impact on the environment."
This is self-serving and unsubstantiated. Some facts to consider:
Halotron I is sold by 80% of the distribution chain for portable fire extinguishers.
The product use life of Halotron I (based on an HCFC) is unlimited.
The restrictions or "non-sustainability" that Rivers refers to pertain to certain production restrictions on virgin raw materials that start after the year 2015. However, material for both re-fill and new production will be available after that date.
The use of the word "sustainable" is misleading given that the shelf life of a fire extinguisher is typically approximately 10 years.
Our experience, as well as that of others, is that end users want clean agents that are approved, acceptable to the authority having jurisdiction, effective on fires and affordable—in that order.
Halotron I is the only halocarbon-based halon 1211 replacement approved by the FAA for both airport ramp use and on-board aircraft use.
Halotron I is UL listed in the widest array of portable and wheeled fire extinguishers—26 different units—tested and listed by UL's offices and facilities.
The environmental profile of Halotron I is, in fact, virtually negligible.
Although we are a fraction of the size of a 3M or DuPont, we believe that our product fills a critical need in the clean-agent market, and we and others believe that it will continue to do so for at least 80% of the U.S. distribution chain for the long term, given the fire-fighting effectiveness, environmental acceptance and affordability.
We were particularly affected by the recent Columbia Space Shuttle accident since we work closely with the program. Each shuttle's solid rocket motor system uses approximately 1,500,000 lbs. of our chemical in the propellant mixture. Thank you for considering my comments in my attempt to clarify your "Clarifying Clean Agents" article, since for us, it hit so close to home.
Jeff Gibson, Director of Operations, Halotron Division, American Pacific Corporation, Las Vegas