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Early lessons from deployment of IFC compatible software

Description: The Industry Foundation Classes (IFC) model of the International Alliance for Interoperability (IAI)-an object data model of buildings-is in its seventh year of development. The last three releases of the model (IFC 1.5.1, 2.0 and 2x) have been implemented by a number of ''mission critical'' industry applications. The deployment of such software in real life projects is just starting. The author is exploring lessons from early deployment that are related to end user and general industry readiness for software interoperability, project model population with data and issues with compatibility of project data, built-in limitations in applications and in the data model, exchange file size and the selection of interoperable software for a project, as well as benefits attainable today from the use of interoperable software. He concludes that software interoperability is beginning to work in this industry, although not as smoothly as first expected.
Date: May 1, 2002
Creator: Bazjanac, V.
Partner: UNT Libraries Government Documents Department

IFC HVAC interface to EnergyPlus - A case of expanded interoperability for energy simulation

Description: Tedious manual input of data that define a building, its systems and its expected pattern of use and operating schedules for building energy performance simulation has in the past diverted time and resources from productive simulation runs. In addition to its previously released IFCtoIDF utility that semiautomates the import of building geometry, the new IFC HVAC interface to EnergyPlus (released at the end of 2003) makes it possible to import and export most of the data that define HVAC equipment and systems in a building directly from and to other IFC compatible software tools. This reduces the manual input of other data needed for successful simulation with EnergyPlus to a minimum. The main purpose of this new interface is to enable import of HVAC equipment and systems definitions, generated by other IFC compatible software tools (such as HVAC systems design tools) and data bases, into EnergyPlus, and to write such definitions contained in EnergyPlus input files to the original IFC files from which building geometry was extracted for the particular EnergyPlus input. In addition, this interface sets an example for developers of other software tools how to import and/or export data other than building geometry from and/or into EnergyPlus. This paper describes the necessary simplifications and shortcuts incorporated in this interface, its operating environment, interface architecture, and the basic conditions and methodology for its use with EnergyPlus.
Date: March 29, 2004
Creator: Bazjanac, Vladimir & Maile, Tobias
Partner: UNT Libraries Government Documents Department

Best practices guide for residential HVAC Retrofits

Description: This best practices guide for residential HVAC system retrofits is aimed at contractors who want guidance on delivering energy efficient, cost effective and innovative products. It has been developed around the idea of having packages of changes to the building HVAC system and building envelope that are climate and house construction dependent. These packages include materials, procedures and equipment and are designed to remove some of the guesswork from a builder, contractor, installer or homeowner decisions about how best to carry out HVAC changes. The packages are not meant to be taken as rigid requirements--instead they are systems engineered guidelines that form the basis for energy efficient retrofits. Similar approaches have been taken previously for new construction to develop extremely energy efficient homes that are comfortable safe and durable, and often cost less than standard construction. This is best epitomized by the Building America program whose partners have built thousands of residences throughout the U.S. using these principles. The differences between retrofitting and new construction tend to limit the changes one can make to a building, so these packages rely on relatively simple and non-intrusive technologies and techniques. The retrofits also focus on changes to a building that will give many years of service to the occupants. Another key aspect of these best practices is that we need to know how a house is working so that we know what parts have the potential for improvement. To do this we have put together a set of diagnostic tools that combine physical measurements and checklists/questionnaires. The measured test results, observations and homeowner answers to questions are used to direct us towards the best retrofits applicable to each individual house. The retrofits will depend on the current condition of the building envelope and HVAC system, the local climate, the construction methods used ...
Date: August 11, 2003
Creator: Walker, Iain S.
Partner: UNT Libraries Government Documents Department

A possible connection between thermal comfort and health

Description: It is a well-established fact that cardiovascular health requires periodic exercise during which the human body often experiences significant physical discomfort. It is not obvious to the exerciser that the short-term pain and discomfort has a long-term positive health impact. Many cultures have well-established practices that involve exposing the body to periodic thermal discomfort. Scandinavian saunas and American Indian sweat lodges are two examples. Both are believed to promote health and well-being. Vacations often intentionally include significant thermal discomfort as part of the experience (e.g., sunbathing, and downhill skiing). So people often intentionally make themselves thermally uncomfortable yet the entire foundation of providing the thermal environment in our buildings is done to minimize the percentage of people thermally dissatisfied. We must provide an environment that does not negatively impact short-term health and we need to consider productivity but are our current thermal comfort standards too narrowly defined and do these standards actually contribute to longer-term negative health impacts? This paper examines the possibility that the human body thermoregulatory system has a corollary relationship to the cardiovascular system. It explores the possibility that we have an inherent need to exercise our thermoregulatory system. Potential, physiological, sociological and energy ramifications of these possibilities are discussed.
Date: May 20, 2004
Creator: Stoops, John L.
Partner: UNT Libraries Government Documents Department

Virtual building environments (VBE) - Applying information modeling to buildings

Description: A Virtual Building Environment (VBE) is a ''place'' where building industry project staffs can get help in creating Building Information Models (BIM) and in the use of virtual buildings. It consists of a group of industry software that is operated by industry experts who are also experts in the use of that software. The purpose of a VBE is to facilitate expert use of appropriate software applications in conjunction with each other to efficiently support multidisciplinary work. This paper defines BIM and virtual buildings, and describes VBE objectives, set-up and characteristics of operation. It informs about the VBE Initiative and the benefits from a couple of early VBE projects.
Date: June 21, 2004
Creator: Bazjanac, Vladimir
Partner: UNT Libraries Government Documents Department

Improving air handler efficiency in houses

Description: Although furnaces, air conditioners and heat pumps have become significantly more efficient over the last couple of decades, residential air handlers have typical efficiencies of only 10% to 15% due to poor electric motor performance and aerodynamically poor fans and fan housings. Substantial increases in performance could be obtained through improved air handler design and construction. A prototype residential air handler intended to address these issues has recently been developed. The prototype and a standard production fan were tested in a full-scale duct system and test chamber at LBNL specifically designed for testing heating, ventilation, and air conditioning systems. The laboratory tests compared efficiency, total airflow, sensitivity to duct system flow resistance, and the effects of installation in a smaller cabinet. The test results showed that the prototype air handler had about twice the efficiency of the standard air handler (averaged over a wide range of operating conditions) and was less sensitive to duct system flow resistance changes. The performance of both air handlers was significantly reduced by reducing the clearance between the air handler and cabinet it was placed in. These test results showed that in addition to the large scope for performance improvement, air handler fans need to be tested in the cabinets they operate in.
Date: May 1, 2004
Creator: Walker, Iain S.
Partner: UNT Libraries Government Documents Department

Establishing the value of advanced glazings

Description: Numerous glazing technologies are under development worldwide to improve the performance of building facades. High-performance glazings can provide substantial energy and related environmental benefits, but often at greatly increased first cost when compared to conventional design solutions. To increase market viability, we discuss strategies to reduce the actual and owner-perceived costs associated with developing and producing advanced window systems, specifically switchable electrochromic glazings, and we also suggest marketing strategies designed to appeal to early adopter and mainstream purchasers. These strategies may be applicable to a broad range of advanced glazing materials.
Date: January 1, 1999
Creator: Lee, E & Selkowitz, S.
Partner: UNT Libraries Government Documents Department

Review of air flow measurement techniques

Description: Airflow measurement techniques are necessary to determine the most basic of indoor air quality questions: ''Is there enough fresh air to provide a healthy environment for the occupants of the building?'' This paper outlines airflow measurement techniques, but it does not make recommendations for techniques that should be used. The airflows that will be discussed are those within a room or zone, those between rooms or zones, such as through doorways (open or closed) or passive vents, those between the building and outdoors, and those through mechanical air distribution systems. Techniques that are highlighted include particle streak velocimetry, hot wire anemometry, fan pressurization (measuring flow at a given pressure), tracer gas, acoustic methods for leak size determination, the Delta Q test to determine duct leakage flows, and flow hood measurements. Because tracer gas techniques are widely used to measure airflow, this topic is broken down into sections as follows: decay, pulse injection, constant injection, constant concentration, passive sampling, and single and multiple gas measurements for multiple zones.
Date: December 1, 2002
Creator: McWilliams, Jennifer
Partner: UNT Libraries Government Documents Department

High-tech buildings - Market transformation project

Description: Facility managers and designers know their buildings are energy intensive yet have few techniques to quantify cleanroom energy performance. Benchmarking identifies the energy end uses in a cleanroom. As expected, besides the process loads, which are often very intense, the mechanical systems are the most energy intensive in these buildings. Benchmarking the mechanical systems and components can provide useful information on system and component performance and provide a basis to identify energy-saving opportunities in cleanrooms. HVAC systems in cleanrooms are dramatically different from their counterparts in commercial buildings in terms of reliability, safety requirements, and scale. The design of cleanroom HVAC systems is a specialty area requiring unique understanding of cleanliness guidelines, airflow quantities, room pressurization, code requirements, specialty equipment, tight control, and many more details. The HVAC systems must also operate reliably and safely. Since recirculation air systems use large amounts of fan power in moving large amounts of conditioned air through HEPA filters, the cleanroom, and return pathways they represent one of the largest energy end uses in a cleanroom. In addition, many processes requiring cleanrooms also have large make-up and exhaust airflow needs requiring huge amounts of energy to move and condition the displaced air. Energy intensity for mechanical systems in cleanrooms ranges between 4 to 100 times that of commercial buildings. There is, however, a lack of comparative data on the performance of cleanroom mechanical systems. To better understand existing cleanroom systems in high technology industries, and to better enable building owners, operators, and designers to compare energy use for a given cleanroom to others, it is necessary to benchmark energy performance in such facilities.
Date: October 1, 2001
Creator: Team, Applications
Partner: UNT Libraries Government Documents Department

LEDS-An overview of the state of the art in technology and application

Description: Solid state lighting in the form of Light Emitting Diodes (LEDs) is bringing new sources with different operating characteristics to the market. With the control in dimension, optics, intensity and color, these sources have the potential to transform the way we use light. This paper will review the recent improvements in performance that have been achieved by these devices, focusing on those product attributes identified as being critical to end users. The paper will conclude with a consideration of applications capitalizing on the LEDs' unique operating and physical properties.
Date: March 1, 2002
Creator: Johnson, Stephen
Partner: UNT Libraries Government Documents Department

Software interoperability for energy simulation

Description: This paper provides an overview of software interoperability as it relates to the energy simulation of buildings. The paper begins with a discussion of the difficulties in using sophisticated analysis tools like energy simulation at various stages in the building life cycle, and the potential for interoperability to help overcome these difficulties. An overview of the Industry Foundation Classes (IFC), a common data model for supporting interoperability under continuing development by the International Alliance for Interoperability (IAI) is then given. The process of creating interoperable software is described next, followed by specific details for energy simulation tools. The paper closes with the current status of, and future plans for, the ongoing efforts to achieve software interoperability.
Date: July 31, 2002
Creator: Hitchcock, Robert J.
Partner: UNT Libraries Government Documents Department

IBECS network/ballast interface: Final report

Description: This report describes the work performed to design, develop, and demonstrate an IBECS network/ballast interface that is useful for economically dimming controllable ballasts in commercial buildings. The first section of the report provides the general background of the IBECS (Integrated Building Environmental Communications System) research and development work as well as the context for the development of the network/ballast interface. The research and development effort that went into producing the first proof-of-concept circuit and the physical prototype of that concept is detailed in the second section. In the third section of the report, we describe the lessons learned from the first demonstration of the network/ballast interface at an office at LBNL. The fourth section describes how electrical noise interference encountered with the first generation of interface led to design changes for a refined prototype that hardened the interface from electrical noise generated by the ballast. The final section of the report discusses the performance of refined prototype after we replaced the proof-of-concept prototype with the refined prototypes in the demonstration office at LBNL.
Date: November 15, 2001
Creator: Rubinstein, Francis & Pettler, Pete
Partner: UNT Libraries Government Documents Department

Development of a California commercial building benchmarking database

Description: Building energy benchmarking is a useful starting point for commercial building owners and operators to target energy savings opportunities. There are a number of tools and methods for benchmarking energy use. Benchmarking based on regional data can provides more relevant information for California buildings than national tools such as Energy Star. This paper discusses issues related to benchmarking commercial building energy use and the development of Cal-Arch, a building energy benchmarking database for California. Currently Cal-Arch uses existing survey data from California's Commercial End Use Survey (CEUS), a largely underutilized wealth of information collected by California's major utilities. Doe's Commercial Building Energy Consumption Survey (CBECS) is used by a similar tool, Arch, and by a number of other benchmarking tools. Future versions of Arch/Cal-Arch will utilize additional data sources including modeled data and individual buildings to expand the database.
Date: May 17, 2002
Creator: Kinney, Satkartar & Piette, Mary Ann
Partner: UNT Libraries Government Documents Department

From design through operations-Results from new construction performance contract and beyond

Description: As part of the High Performance Commercial Building Systems program, LBNL has been working with the City of Oakland to understand the ongoing performance of the Oakland Administration Buildings. The primary objective of this research is to understand the performance targets and ongoing performance of two buildings that were the subject of a new construction performance contract. Secondary objectives include examining the building performance information systems developed as part of the new construction performance contract and evaluating the role of the energy management and control system (EMCS) as a data acquisition tool to provide recommendations for future new construction projects. We examine the results of the performance contract in detail, and provide additional performance metrics that go beyond what was required in the performance contract. We found that the energy cost intensities (ECI) linked to the project ranged from $1.08/ft{sup 2} to $1.44/ft{sup 2}. Changes in floor area, energy costs, rate schedules, and energy use complicate the evaluation of the performance because of the lack of tracking of underlying data and assumptions. Overall, Oakland has two large office buildings with relatively low-energy use (50 kBtu/ft{sup 2}-yr site electricity and gas use). We compare this energy-use intensity with a number of related benchmarks. Additional end-use, HVAC performance, and diagnostics data are discussed.
Date: May 17, 2002
Creator: Motegi, Naoya; Piette, Mary Ann & Wentworth, Scott
Partner: UNT Libraries Government Documents Department

Investigation of the persistence of new building commissioning

Description: Commissioning is gaining increasing recognition as a cost-effective strategy for reducing commercial building energy use. Although the success and cost-effectiveness of commissioning projects depends on how well the benefits of commissioning persist over time, this aspect of commissioning is not well understood. The persistence of commissioning benefits was recently studied in a PIER project evaluating ten buildings that were commissioned at building start-up at least two years ago. The researchers examined the commissioning reports, control algorithms, EMCS point measurements, and energy use data, and conducted operator and commissioning provider interviews to investigate the persistence of commissioning benefits. In addition, they conducted site visits in a sample of the buildings. A set of commissioning measures was selected for each building to compare the persistence of benefits. Persistence was measured both qualitatively through a discussion of occupant comfort and decreased maintenance and quantitatively through estimations of energy savings. This paper reports the results of the study. The discussion includes how well the benefits of commissioning persisted over time, reasons for declining performance, and methods for improving persistence. The results provide valuable insight into how to estimate the persistence of commissioning information central to the cost benefit analyses routinely performed for commissioning measures.
Date: March 17, 2002
Creator: Potter, Amanda; Friedman, Hannah; Haasl, Tudi & Claridge, David
Partner: UNT Libraries Government Documents Department

Lithium-based electrochromic mirrors

Description: Antimony, antimony-copper, and antimony-silver thin films were prepared by DC magnetron sputtering on glass substrates. Their reflectance and transmittance in the visible range were measured before and after electrochemical lithiation. The mixed metal films exhibited larger changes in reflectance and small shifts in the optical absorption edge compared with pure antimony films. Electrochromic cycling speed and stability of the Sb-Li system were improved by the addition of copper and silver.
Date: May 19, 2003
Creator: Richardson, Thomas J. & Slack, Jonathan L.
Partner: UNT Libraries Government Documents Department

Experimental evaluation of gas filled plenum (GFP) insulation for ducts

Description: Forced-air heating and cooling system ducts are often located outside conditioned space in US houses. For these systems to perform efficiently it is important that these ducts be well insulated. Common practice is to use a glass fiber wrap around the ducts--either field applied or more commonly, integrated into a flexible duct. Most duct insulation has an R-value of 4.2, with R6 and R8 ducts also occasionally used. With glass fiber insulation being about R4 per inch (RSI 0.28/cm), this adds 2 to 4 inches (50 to 100 mm) to the duct diameter. Some building codes are now requiring these higher insulation levels, for example, the EPA requires the use of R6 ducts (for Energy Star ducts), and International Energy Conservation Code (BOCA 2003) requires R8 ducts. The difficulty with adding insulation to ducts is the increase in diameter of the ducts that makes them expensive to transport because they take up a large volume and are difficult to install in the confined spaces available for ducts in houses. The objective of this study was to evaluate Gas Filled Plenum (GFP) technology as an alternative duct insulation. GFP ducts have the potential to provide greater insulation levels than existing ducts (for a given thickness of insulation or size of duct) and provide cost savings in transportation. These transportation cost savings are based on the idea of shipping the GFP ducts empty and inflating them on-site. To evaluate this technology for ducts we constructed a prototype duct and determined both its flow and heat transfer resistance in LBNL's duct testing laboratories. The GFP technology works by encapsulating a gas (usually air--but other noble gases such as Argon or Krypton can provide significant increases in thermal resistance with increased cost) in a metalized film jacket. A honeycomb structure is used to keep ...
Date: January 26, 2003
Creator: Walker, Iain S. & Guillot, Cyril
Partner: UNT Libraries Government Documents Department

The integration of engineering and architecture: A perspective on natural ventilation for the new San Francisco Federal Building

Description: A description of the in-progress design of a new Federal Office Building for San Francisco is used to illustrate a number of issues arising in the design of large, naturally ventilated office buildings. These issues include the need for an integrated approach to design involving the architects, mechanical and structural engineers, lighting designers and specialist simulation modelers. In particular, the use of natural ventilation, and the avoidance of air-conditioning, depends on the high degree of exposed thermal mass made possible by the structural scheme and by the minimization of solar heat gains while maintaining the good daylighting that results from optimization of the fagade. Another issue was the need for a radical change in interior space planning in order to enhance the natural ventilation; all the individual enclosed offices are located along the central spine of each floorplate rather than at the perimeter. The role of integration in deterring the undermining of the design through value engineering is discussed. The comfort criteria for the building were established based on the recent extension to the ASHRAE comfort standard based on the adaptive model for naturally ventilated buildings. The building energy simulation program EnergyPlus was used to compare the performance of different natural ventilation strategies. The results indicate that, in the San Francisco climate, wind-driven ventilation provides sufficient nocturnal cooling to maintain comfortable conditions and that external chimneys do not provide significant additional ventilation at times when it when it would be beneficial.
Date: May 31, 2002
Creator: McConahey, Erin; Haves, Philip & Christ, Tim
Partner: UNT Libraries Government Documents Department

Measurement of airflow in residential furnaces

Description: In order to have a standard for furnaces that includes electricity consumption or for the efficiency of furnace blowers to be determined, it is necessary to determine the airflow of a furnace or furnace blower. This study focused on airflow testing, in order to determine if an existing test method for measuring blower airflow could be used to measure the airflow of a furnace, under conditions seen in actual installations and to collect data and insights into the operating characteristics of various types of furnace blowers, to use in the analysis of the electricity consumption of furnaces. Results of the measured airflow on furnaces with three types of blower and motor combinations are presented in the report. These included: (1) a forward-curved blower wheel with a typical permanent split capacitor (PSC) motor, (2) a forward-curved blower wheel with an electronically-commutated motor (ECM), and (3) a prototype blower, consisting of a backward-inclined blower wheel matched to an ECM motor prototype, which is being developed as an energy-saving alternative to conventional furnace blowers. The testing provided data on power consumption, static and total pressure, and blower speed.
Date: January 24, 2004
Creator: Biermayer, Peter J.; Lutz, James & Lekov, Alex
Partner: UNT Libraries Government Documents Department

A systems approach to retrofitting residential HVAC systems

Description: A Best Practices Guide for retrofitting residential HVAC systems has recently been completed by DOE. The guide uses diagnostics and checklists to guide the user to specific retrofit packages that maximize retrofit energy savings, comfort and safety potential. The guide uses a systems approach to retrofitting where the interaction of different building components is considered throughout the retrofit selection process. For example, added building envelope insulation reduces building loads so that smaller capacity HVAC systems can be used. In this study, several houses were surveyed using the Best Practices Guide and a single house was selected for retrofitting. The objectives were to demonstrate how a successful system-wide retrofit can be carried out and to provide feedback to improve the guide. Because it represents a departure from current practice, a key aspect of this study was to investigate the interactions with contractors and code officials who are unfamiliar with the systems approach. The study found that the major barrier to the systems approach in retrofits was in changing the working practices of contractors and code officials.
Date: May 1, 2004
Creator: McWilliams, J.A. & Walker, I.S.
Partner: UNT Libraries Government Documents Department

Experimental evaluation of gas filled plenum (GFP) insulation for ducts

Description: Forced-air heating and cooling system ducts are often located outside conditioned space in US houses. For these systems to perform efficiently it is important that these ducts be well insulated. Common practice is to use a glass fiber wrap around the ducts--either field applied or more commonly, integrated into a flexible duct. Most duct insulation has an R-value of 4.2, with R6 and R8 ducts also occasionally used. With glass fiber insulation being about R4 per inch (RSI 0.28/cm), this adds 2 to 4 inches (50 to 100 mm) to the duct diameter. Some building codes are now requiring these higher insulation levels, for example, the EPA requires the use of R6 ducts, and International Energy Conservation Code (BOCA 2003) requires R8 ducts. The difficulty with adding insulation to ducts is the increase in diameter of the ducts that makes them expensive to transport because they take up a large volume and are difficult to install in the confined spaces available for ducts in houses. The objective of this study was to evaluate Gas Filled Plenum (GFP) technology as an alternative duct insulation. GFP ducts have the potential to provide greater insulation levels than existing ducts (for a given thickness of insulation or size of duct) and provide cost savings in transportation. These transportation cost savings are based on the idea of shipping the GFP ducts empty and inflating them on-site. To evaluate this technology for ducts we constructed a prototype duct and determined both its flow and heat transfer resistance in LBNL's duct testing laboratories. The GFP technology works by encapsulating a gas (usually air--but other noble gases such as Argon or Krypton can provide significant increases in thermal resistance with increased cost) in a metalized film jacket. A honeycomb structure is used to keep individual gas pockets small ...
Date: January 26, 2003
Creator: Walker, Iain S. & Guillot, Cyril
Partner: UNT Libraries Government Documents Department

Associations of indoor carbon dioxide concentrations, VOCS, environmental susceptibilities with mucous membrane and lower respiratory sick building syndrome symptoms in the BASE study: Analyses of the 100 building dataset

Description: Using the 100 office-building Building Assessment Survey and Evaluation (BASE) Study dataset, we performed multivariate logistic regression analyses to quantify the associations between indoor minus outdoor CO{sub 2} (dCO{sub 2}) concentrations and mucous membrane (MM) and lower respiratory system (Lresp) Sick Building Syndrome (SBS) symptoms, adjusting for age, sex, smoking status, presence of carpet in workspace, thermal exposure, relative humidity, and a marker for entrained automobile exhaust. Using principal components analysis we identified a number of possible sources of 73 measured volatile organic compounds in the office buildings, and assessed the impact of these VOCs on the probability of presenting the SBS symptoms. Additionally we included analysis adjusting for the risks for predisposition of having SBS symptoms associated with the allergic, asthmatic, and environmentally sensitive subpopulations within the office buildings. Adjusted odds ratios (ORs) for statistically significant, dose-dependant associations (p<0.05) for dry eyes, sore throat, nose/sinus congestion, and wheeze symptoms with 100-ppm increases in dCO{sub 2} ranged from 1.1 to 1.2. These results suggest that increases in the ventilation rates per person among typical office buildings will, on average significantly reduce the prevalence of several SBS symptoms, up to 80%, even when these buildings meet the existing ASHRAE ventilation standards for office buildings. VOC sources were observed to play an role in direct association with mucous membrane and lower respiratory irritation, and possibly to be indirectly involved in indoor chemical reactions with ozone that produce irritating compounds associated with SBS symptoms. O-xylene, possibly emitted from furniture coatings was associated with shortness of breath (OR at the maximum concentration = 8, p < 0.05). The environmental sensitivities of a large subset of the office building population add to the overall risk of SBS symptoms (ORs ranging from 2 to above 11) within the buildings.
Date: October 1, 2002
Creator: Apte, M.G. & Erdmann, C.A.
Partner: UNT Libraries Government Documents Department

Dimming every light cheaply

Description: This paper discusses the successful development and testing of the first ballast/IBECS network interface that will allow commercially-available controllable ballasts to be operated from the Internet via IBECS (Integrated Building Environmental Communications System). The interface, which is expected to cost original equipment manufacturers (OEMs) only about $1-2/unit, has been hardened so that it is impervious to electronic noise generated by most 0-10 VDC controllable ballasts.
Date: March 27, 2002
Creator: Rubinstein, Francis; Pettler, Peter & Jennings, Judith
Partner: UNT Libraries Government Documents Department