Building Energy Use and Control Problems: Defining the Connection Revised

National Building Controls Information Program Sponsors United States Environmental Protection Agency Iowa Energy Center

2521 Elwood Drive, Suite 124 Ames, IA 50010-8229 515-294-8819 or fax 515-294-9912 Email: [email protected] Web sites: www.energy.iastate.edu www.ddc-online.org www.buildingcontrols.org

NBCIP Report: NBCIP/02/01.1 May, 2002 This report contains minor revisions of NBCIP Report: NBCIP/02/01 ABSTRACT The National Building Controls Information Program (NBCIP) was established on the premise that properly functioning control systems are a significant contributor to energy efficiency, and problems associated with building controls and operation are a primary cause of inefficient energy usage. The initial effort of the NBCIP has been to undertake a literature review to define the relationship between energy consumption in buildings and control-related problems. The focus of the review was on case studies of real buildings. In all, 67 case studies were considered, in which the control-related problems of more than 110 buildings were described. Over 380 controlrelated problems were reported. Software problems were found to be the most prevalent type of problem, followed closely by hardware problems. Human factor problems occurred less frequently but were still significant. Within the subcategories defined, problems stemming from programming occurred at a significantly higher rate than any other subcategory of problem. In general, information about the energy impact of controlrelated problems was lacking in the case studies and will need to be determined through other means.

Building Energy Use and Control Problems: Defining the Connection

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1. INTRODUCTION The National Building Controls Information Program (NBCIP) has been created at the Iowa Energy Center with sponsorship from the United States Environmental Protection Agency (EPA). The NBCIP was established on the premise that properly functioning control systems are a significant contributor to energy efficiency, and problems associated with building controls and operation are a primary cause of inefficient energy usage. Within the context of the NBCIP, building controls and control systems refer to the input devices, controllers, and controlled devices that are components of direct digital control (DDC) systems that operate buildings. Pneumatic controllers are outside the scope of the NBCIP. First a look at the positive. It is commonly understood among HVAC professionals that DDC systems can improve the energy performance of a building (ASHRAE, 2000). Hicks and von Neida

Frequency of Common Problems

Figure 1: Frequency of common problems encountered in a 60 building study performed by Lawrence Berkeley National Laboratories (LBNL, 2002).

50% 40%

25%

(2000) found that Energy Star office buildings had an average site energy intensity that was 44% lower than the market average determined from office buildings in the Commercial Building Energy Consumption Survey (CBECS) database (EIA, 1998). Energy Star buildings typically employed energy management and control systems (EMCS), variable speed drives (VSD), economizers, and energy efficient equipment. However, these same technologies were also found to be prevalent in the least energy efficient CBECS buildings. Thus, while control systems can be a significant contributor to energy efficiency, EPA staff concluded that technology alone cannot deliver this efficiency. To quote: “A combination of operation and practice, and strong management commitment are necessary ingredients for success” (Lupinacci, 2001). The CBECS buildings reported on by Hicks and von Neida (2000) illustrate that the mere presence of an EMCS does not ensure superior energy performance. Numerous studies support the premise that problems with building controls are a primary cause of inefficient energy use. One study estimates failure rates of economizers of 50% and higher, with resultant energy waste far exceeding energy savings that can be achieved when they operate properly (Lunneberg, 1999). Another study estimates that about one-sixth of Oregon K-12 schools have “dysfunctional DDC systems” leading to energy waste in excess of $1 million per year (Churchill, 2000). In a 60 building study, researchers at Lawrence Berkeley National Laboratories found that 50% of the buildings had controls problems; 40% had HVAC equipment problems; 25% had energy management systems (EMS), economizers, and/or VSD that were not functioning properly; and 15% had missing equipment (LBNL, 2002). (see Figure 1)

15%

Controls

HVAC Equipment

EMS, Economizers & VSD

Missing Equipment

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Researchers at the Texas A&M University Energy Systems Laboratory estimated potential energy savings of nearly $4,000,000 per year due to operations and maintenance (O&M) measures in 132 buildings, of which 77% of the savings could be achieved through correcting controls problems (Claridge et al., 1994). (see Figure 2) Finally, researchers at the University of Colorado performed a number of commissioning activities primarily involving changes to the software and hardware of the control system of a building constructed in 1991 (Brandemuehl and Bradford, 1998). In 1996, these changes produced energy savings of 16% compared to 1995, and 25% compared to 1994. This study illustrates how well and how poorly a building can perform because of its control system. The studies described above demonstrate that control-related problems are a significant contributor to energy waste in buildings. But that need not be the case. The challenge now is to under-

Figure 2: Distribution of potential O&M savings among major types of O&M measures (Claridge et al., 1994). 1% Delamping

stand what parts of building control systems are responsible for the problems that produce energy waste. With this understanding, a course can be set to alleviate such problems. The literature review of published technical documents described in the next section is a first step towards gaining that understanding. 2. ABOUT THE REVIEW The initial effort of the NBCIP has been to undertake a literature review to define the relationship between energy consumption in buildings and control-related problems. The review included an extensive survey of HVAC trade publications, proceedings of building and HVAC-related conferences, and reports from federal, state, and university-based energy laboratories and agencies as well as private companies offering building services. This effort culminated in a report prepared for the NBCIP (Ardehali and Smith, 2001). The focus of the review was on actual case studies of buildings. In all, 67 case studies were considered, in which the control-related problems of more than 110 buildings were described. Over 380 control-related problems were reported. One of the objectives of the review was to categorize the control problems as much as possible. To that end, the following first-level categories were defined: 1. Hardware related 2. Software related 3. Human factor related

22% Traditional O&M

77% Control System

A fourth category labeled “unspecified” was defined to accommodate control problems lacking sufficient detail for assignment in the other categories. Problems in the actual HVAC equipment (e.g., chiller, pump, air-handling unit, etc.) were not considered.

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3. FINDINGS The literature review produced the following findings (see Figure 3): • 35% of the problems were software related, • 32% of the problems were hardware related, • 21% of the problems were human factor related, and • 12% of the problems were unspecified. These findings indicate that control problems with software and hardware are the most prevalent, although a significant fraction of the problems are attributed to human factors. It should be pointed out that there is uncertainty in the findings. Many studies cited economizer problems without indicating whether the problems were predominantly hardware related (e.g., broken damper linkages), software related (e.g., unstable control loop caused by the use of incorrect tuning parameters), or human factor related (e.g., outdoor air damper propped open with a two-by-four). Undiagnosed problems of this type were placed in the unspecified category. Uncertainty also exists within the hardware, software, and human factor categories, stemming mainly from the challenge of distinguishing a problem from a symptom. For instance, a symptom might be a broken linkage in a damper actuator, while the real problem might be a poorly tuned control loop causing premature failure of the linkage. If the problem cited was a broken linkage, it was assigned to the hardware category. 4. DIGGING DEEPER The first level categories are quite broad and greater specificity would be helpful in identifying the true nature of control problems. Therefore, the subcategories described below were established. One or more examples of typical control problems that would be assigned to each subcategory are also provided.

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Hardware related

Input device – Refers to problems associated with sensors, transducers, switches, relays, and related devices used for measuring or indicating some condition. Examples of input devices include temperature sensors, pressure differential sensors, and power transducers. Example: a control problem stemming from a malfunctioning or improperly located sensor. Controller – Refers to problems associated with the hardware device that receives sensor input data, executes control logic on those data, and causes an output action to be generated. Example: an electronic failure of a circuit board. Controlled device – Refers to problems with the device that receives output signals from controllers and changes the state of an end device. Examples of controlled devices include valve operators, damper operators, electric relays, and variable speed drives. Example: a leaking control valve.

Figure 3: Categorization of control problems.

12% Unspecified

35% Software 21% Human Factor

32% Hardware

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Communication – Refers to problems associated with the hardware necessary for transmitting analog signals, digital signals, and network communications between components of the control system. Examples of communication hardware include wiring, cabling, communications interfaces, and gateways. Example: a control problem stemming from delays due to excessive traffic on the control network, or a disconnected or loose wiring termination for a sensor.

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Software related

Input/Output Implementation – Refers to problems arising from the configuration of input and output points that occur prior to turning over the EMCS to the building operator. Example: incorrect high and low span values, selection of the wrong sensor type from a dropdown menu, and incorrect addressing. Programming – Refers to problems arising from incorrect or inappropriate control logic and parameters that produce output to control HVAC equipment. Example: improper reset control strategies and setpoints, gain coefficients for control loops, and sequencing of equipment. Data Management – Refers to problems associated with producing information from data including data monitoring, display, alarming, and logging. Example: inability of application specific controllers to trend data necessary for control monitoring and diagnostics, and false alarms. Operation System – Refers to problems associated with the operation of the EMCS software and its interface to the computer operating system. Example: loss of control setpoints and/or parameters due to a power outage or a file download.

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maintenance that unintentionally result in improper operation of a system. Example: failure to release an operator override that was implemented to allow system maintenance, or failure to perform required sensor calibrations. Operator unawareness – Refers to problems arising from an operator’s lack of understanding or familiarity with the control system due to inadequate training. Example: changing control logic to compensate for a problem, only to have the changes produce additional control problems. Operator interference – Refers to problems associated with intentional changes to the control system made by the operator causing interference with the normal operation of the system. Example: disconnecting controllers, obstructing control devices, and disabling control points through software or hardware changes. Operator indifference – Refers to any number of control problems stemming from an operator’s apathy toward operation and maintenance. All of the control problems in the hardware, software, and human factor categories were classified into one of these subcategories. Because of the uncertainty of the classifications, the results are presented in a qualitative manner in Figure 4. Figure 4 illustrates that problems stemming from programming have a significantly higher rate of occurrence than any other subcategory. Problems associated with input devices, controlled devices, operator error, and operator interference are also prevalent. Despite the qualitative nature of the assessment, the findings provide valuable guidance with regard to where the NBCIP efforts should be directed.

Human factor

Operator error – Refers to problems associated with changes to the control system made by the operator during routine operation and maintenance as well as failure to perform routine operation and

5. WHAT’S MISSING? The goal of the literature review was to identify existing case studies where inefficient energy use in buildings has been tied to control performance

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Figure 4: A refinement of the categorization of control problems. Qualitative Representation of the Occurrence Rate of Control Problems

Occurrence Rate

High

Medium

Low

Hardware Related

Software Related

Human Factor Related

g n s t m ce ation er ce ce e or atio min yste emen nes evi evi roll Err ren c enc S ent gram t D Cont d D muni g tor aware terfe differ u n a e a m l r p l o n o i e n e l r a t I n n In m ro I p p a P r t U r o M r O o n m e r C t to ta tI to Co Op era Da era era tpu Op Op Op Ou ut/ p n I

problems. The findings of the review shed considerable light on the types of control problems that occur most frequently; however, the energy impact of these problems is more difficult to ascertain. In general, the case studies reviewed did not provide sufficient information to determine the percentage of energy savings that could be achieved through a reduction or elimination of control problems stemming from the individual categories and subcategories. Quantifying the energy savings potential would require information from additional sources. These sources may include: 1. new case studies conducted specifically to determine the energy impact of control problems in various categories and subcategories; 2. simulation studies wherein normal operation of HVAC equipment is altered to account for control problems and energy use is

compared to baseline energy use for normal operation; and 3. control systems experts. In the near term, the intent is to draw on the collective knowledge of controls experts to help complete this picture. Once the energy impact of the various subcategories of control problems has been established, the next step will be to identify what subcategories of problems lend themselves to improvement and the best method of achieving improvement. In certain cases product testing may be appropriate, while in others the best method of achieving improvement may be through the dissemination of product independent information, such as energy efficient control strategies. Ultimately, the NBCIP will place a high priority on subcategories of control problems that occur frequently, have a substantial energy impact, and lend themselves to improvement either through product testing or through more general means. 6. CONCLUSIONS The NBCIP was established on the premise that properly functioning control systems are a significant contributor to energy efficiency, and problems associated with building controls and operation are a primary cause of inefficient energy usage. The case studies reviewed provide substantial evidence supporting the latter premise. Software problems were found to be the most prevalent type of problem, followed closely by hardware problems. Human factor problems occurred less frequently but were still significant. Within the subcategories defined, problems stemming from programming occurred at a significantly higher rate than any other subcategory of problem. The next steps are to determine the subcategories of problems that have the largest energy impact and those that lend themselves to improvement. This information will be used to shape the agenda for future NBCIP efforts.

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REFERENCES Ardehali, M. M. and T. F. Smith. 2001. Literature Review to Identify Existing Case Studies of Controls-Related Energy-Inefficiency in Buildings. Prepared for the National Building Controls Information Program. Technical Report ME-TFS-01-007. Dept. of Mechanical Engineering, The University of Iowa, Iowa City, Iowa. ASHRAE. 2000. ASHRAE Guideline 13-2000: Specifying Direct Digital Control Systems. American Society of Heating Refrigerating and Air Conditioning Engineers, Inc.: Atlanta, Georgia. Brandemuehl, M. J. and J. Bradford. 1998. Implementation of On-Line Optimal Supervisory Control of Cooling Plants Without Storage. JCEM Technical Report TR/98/3. Joint Center for Energy Management, University of Colorado, Boulder, Colorado.

Energy Efficiency in Buildings Proceedings. American Council for an Energy Efficient Economy: Washington, D.C. LBNL. 2002. http://buildings.lbl.gov/hpcbs/Year_01/Element_5/ 01_E5.html Lunneberg, T. 1999. When Good Economizers Go Bad. E Source Report ER-99-14. Lupinacci, J. M. 2001. “The Importance of Commissioning in Achieving Excellence in Energy Performance.” Proceedings of the 9th National Conference on Building Commissioning. Cherry Hill, New Jersey.

Churchill, G. 2000. “The Direct Digital Control Crisis in Oregon Public Schools: Offering Solutions Through Trouble-Shooting Services, Construction Specifications and DDC Circuit Rider Services.” ACEEE 2000 Summer Study on Energy Efficiency in Buildings Proceedings. American Council for an Energy Efficient Economy: Washington, D.C. Claridge, D. E., J. Haberl, M. Liu, J. Houcek, and A. Athar. 1994. “Can You Achieve 150% of Predicted Retrofit Savings? Is it Time for Recommissioning?” ACEEE 1994 Summer Study on Energy Efficiency in Buildings Proceedings. American Council for an Energy Efficient Economy: Washington, D.C. EIA. 1998. A Look at Commercial Buildings in 1995: Characteristics, Energy Consumption, and Energy Expenditures. Energy Information Administration, United States Department of Energy: Washington, D.C. Hicks, T. W. and B. von Neida. 2000. “An Evaluation of America’s First ENERGY STAR® Buildings: The Class of 1999.” ACEEE 2000 Summer Study on

2521 Elwood Drive, Suite 124, Ames, IA 50010-8229 515-294-8819 or fax 515-294-9912 Email: [email protected] Web sites: www.energy.iastate.edu www.ddc-online.org www.buildingcontrols.org

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