BTL Mark: Resolve interoperability issues & increase buyer confidence
M. Phillips, Staff Engineer
The importance of building commissioning and tune-ups has recently taken center stage. Traditional methods used to analyze building systems and diagnose problems are unfortunately fraught with shortcomings. System-wide performance monitoring offers a more powerful, scientific approach to building system analysis.
When a patient enters an examination room with a chest pain, the doctor does not simply hand the patient a prescription drug. The doctor understands, as do most of us, that the individual's pain is most likely a symptom of a more complex problem. To determine the nature of the problem, the doctor will question the individual and perform an initial examination from which he will usually determine further courses of action. However, he knows that he cannot be certain of his diagnosis until thorough, unbiased tests are performed that look at the inner workings of the individual, and not just address the outlying symptoms.
This strategy forms the foundation for system-wide performance monitoring of buildings. Just like a doctor's systematic approach to his ill patient, the system-wide performance monitoring method provides a complete systematic diagnostic approach for a building, and examines every critical aspect of the indoor environment, HVAC system, controls, and lighting system. The symptoms are just one piece of information used to understand the building; performance monitoring provides the rest.
System-Wide Performance Monitoring
Through the years, various methods have been developed to assess operation and maintenance (O&M) practices and diagnose problems within building systems. Most of these methods have been developed to observe specific portions of a system or look at the system for one instant in time. These methods assume that building systems are static, and that conditions within the building generally remain the same. Furthermore, they assume individual parts of a system act independently of one another. However, today we know that building systems are dynamic, and constantly being affected by people, weather, and the indoor environment. We also realize that each portion of a system affects and is affected by every other part of the system. Consequently, in order to understand the underlying problems within a system, one must take a more encompassing monitoring approach and study the entire system and its surroundings over long enough periods of time to see the problem.
Following this philosophy, Architectural Energy Corporation (AEC) in collaboration with the Electric Power Research Institute (EPRI) has developed an integrated hardware and software tool that includes the MicroDataLoggers® portable data acquisition system and the ENFORMA® Portable Diagnostic Solution software to monitor building systems over specific periods of time. This method of system-wide monitoring yields time-synchronized performance data that documents the interaction of system components with one another and their surrounding environment. Additionally, the ENFORMA software utilizes engineering databases and series of algorithms to develop diagnostic plots of critical relationships in a building system, relieving the engineer from having to sort through tedious spreadsheets and large data files.
Shortcomings of Traditional O&M Assessment
Various methods for studying O&M practices and observing building systems have been developed to aid in building commissioning and tune-ups. Traditional O&M assessment methods include on-site auditing, spot-testing, utility bill analysis, and EMS trend logs. Typically, combinations of these various methods will be utilized in an effort to form a more complete analysis of building systems.
During an on-site audit, a walkthrough is performed in which the building is visually inspected. Building operators and maintenance personnel are usually interviewed and documentation is studied in order to obtain an understanding of existing O&M procedures. This method usually detects problems of a more obvious nature such as dirty filters, loose belts, failing insulation, and leaks, but has limited ability to probe dynamic system conditions.
Spot-checking equipment with hand-held instruments can provide some greater depth into understanding a system, but this method only provides a glimpse of the system at a specific instant in time. Additionally, utility bill analysis can provide further information, and is often used to demonstrate that a problem exists, but can provide very little conclusive data toward identifying the sources of suspected problems.
Energy management system (EMS) point trending provides a more complete look at the system, but is ultimately crippled by inherent limitations. First, sampling rates are often too slow to discover most problems. Also, memory is limited so large data sets cannot be saved into one file, and only small sets of data points can be trended at one time. Furthermore, consistent time-series data may be difficult to gather. Finally, monitoring points may be missing from the EMS that are critical to determining operational problems.
Using System-Wide Diagnostic Monitoring to
Find O&M Problems
System-wide diagnostic monitoring develops a complete analysis of a system, and is capable of uncovering a wide range of problems, which would be difficult -- if not impossible -- to find by any other means. Applying a systematic method to building system analysis includes three key components:
System information is entered into the software, and a monitoring plan is automatically developed illustrating monitoring points and the sensors needed. The software configures data logging hardware with the needed sensors attached, and the technician installs the equipment.
Logging automatically starts simultaneously at a pre-set start time, and data is acquired at desired sample interval rates for a specific duration, typically two weeks. Hardware is retrieved and data is downloaded, converted, and manipulated by the software. Data can also be used from existing points on the EMS.
Load shapes and diagnostic plots are automatically generated, and the user performs analysis. If necessary, data may be exported to calibrate modeling software such as DOE-2.
According to one State Energy Management Administrator, "The use of data loggers raised my department's level of confidence that we were finding the core problems in all our building systems. The software's ability to show key system relationships took away the guesswork and the equipment has become a critical tool for our future commissioning efforts."
Tools for system-wide monitoring were designed by engineers for engineers as a means to solve building system problems with a level of rigor that results in cost-effective solutions. Some general types of operational problems commonly uncovered using this method are:
Scheduling -- equipment found on at night, weekends, and during other times when it was assumed to be off
System operation above or below set-point, or not meeting loads
Excessive cycling of equipment
Malfunctioning control hardware (economizers, etc.)
EMS control loops not working optimally
Controls permanently overridden by building operators
Heating and cooling system interaction problems
Raising the Diagnostic Process to a New Level
Only when tools were developed for doctors that eased the effort and cost involved in diagnosing a patient did it become common to perform more advanced testing and monitoring on patients. By providing tools that do the same for professionals performing commissioning services, building tune-ups, O&M and energy services, the more systematic approach of system-wide performance monitoring has become essential to the building industry.
Detailed information about MicroDataLoggers and the Enforma system is available at www.archenergy.com or by calling AEC at #800-450-4454.
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