Capitol Mall Office Building
This demonstration of the Whole-Building Diagnostician (WBD), documents the online analysis of data for the service-provider demonstration. Battelle working with Newport Design Consultants (NDC) implemented the online test configuration, data collection, data analysis, and documentation for this demonstration. The online test was designed to assess the usability, usefulness, and value of the WBD for providers of HVAC services, in this case by Marina Mechanical. It was also to evaluate the Outdoor-Air Economizer (OAE) diagnostic module’s capabilities to automatically and continually diagnose operational problems with air-handling units (AHUs).
The service provider demonstration took place at the Capitol Mall Building in Sacramento. The Capitol Mall building is an 18-story 385,000 square foot premier “Class A” office building with integral covered parking structure. The building, other than office space, houses a Café, rooftop terrace and balconies. The building was built in 1984 and is located at 300 Capitol Mall approximately six blocks west of the State Capitol. The building is an Environmental Protection Agency “Energy Star” qualified building. Buildings, which are “Energy Star” qualified, use about 40 percent less energy than average buildings, without compromising comfort or services.
Off-line data were collected for a period between May 17, 2001 and May 24, 2001 and the on-line data between September 19, 2002 and March 27, 2003. The buildings HVAC systems consist of two variable speed drive centrifugal chillers of 500 tons each and one natural gas hydronic boiler of 7,000,000 Btu/hr., both hydronic systems are constant volume. Six large variable-air-volume (VAV) air handlers with heating and cooling coils, differential dry-bulb controlled economizers and variable speed drives (see Table 1) serve the occupied space. The air-handlers provide heating and cooling to the occupied spaces through variable volume zone boxes without reheat coils. A direct digital control (DDC) system from American Auto-Matrix controls the HVAC systems, which also provides a mechanism for trend logs
As part of this online demonstration all six AHUs at 300 Capitol Mall were monitored. The measured data that were collected on a continuous basis included: 1) outdoor-air temperature, 2) return-air temperature, 3) mixed-air temperature, 4) supply-air temperature, 5) chilled-water valve position, 6) supply-fan status, 7) hot-water valve position, 8) supply-air set point, and 9) economizer damper position.
| Air-Handling Unit | Rated Flow (ft3/min) |
|
| AHU-1 | 100,000 | |
| AHU-2 | 100,000 | |
| AHU-3 | 40,000 | |
| AHU-4 | 40,000 | |
| AHU-5 | 50,000 | |
| AHU-6 | 50,000 |
The air handler’s control strategy for the outdoor-air and economizer, and the schedule (times of day and days of week) for which the minimum outdoor air must be supplied for the occupants was entered into the WBD’s configuration for the air handler. For online tests, the data from the AHUs was automatically collected using trend logs and logged into the diagnostician’s database using a data collection module, which is also part of the WBD. Although the data requests can be made at any frequency, at Capitol Mall, the data was requested at 5-minute intervals and integrated over the hour before being processed by the OAE diagnostic module. The online data collection process started in September of 2002 for all six AHUs.
All six AHUs at Capitol Mall had outstanding problems. The predominant problems for each of the six AHUs are: 1) AHU-1 had the damper not fully opening during economizer operations, 2) AHU-2 had the damper not fully opening during economizer operations and excess ventilation during the heating mode, 3) AHU-3 had the damper not fully opening during economizer operations and excess ventilation during the heating mode, 4) AHU-4 had the damper not fully opening during economizer operations, 5) AHU-5 had the damper not fully opening during economizer operations and excess ventilation during the heating mode, and 6) AHU-6 had excess ventilation during the heating mode.
The controls service provider and WBD site Administrator at the Capitol Mall building indicated that the WBD diagnostic tool was quite comprehensive and would provide building managers, operators, and owners with the ability to evaluate real-time data and perform corrective measures as required. He also indicated that the user interface for both the WBD and the OAE diagnostician was difficult to use. Although the problems identified by the OAE diagnostician were confirmed at the site by the service provider, none of the problems were corrected (see Section 8 for more details on why the problems were not corrected). In addition, the building operators were given a presentation of the WBD but none of them actually reviewed the results during the demonstration. This may be a critical missing link in the process of using such tools and needs further investigation in future applications.
The OAE diagnostician was shown to successfully identify problems with all six AHUs at the Capitol Mall building. These findings are consistent with the other field demonstrations of the WBD, where the OAE found similar problems that should have been detected at the time of commissioning. The demonstration showed that diagnostic technology is only as good as the fixes to the problems it identifies. That is, it is insufficient to merely identify problems and their impacts and expect operators will fix them as a result. If users are not proficient in using their control systems to correct problems, are too busy with other duties, or lack resources to obtain help from contractors, diagnostic technologies alone will not result in system efficiency improvements. Improvements can only be realized in buildings where identified problems are corrected.
Click here for the "Enhancing Building Operations through Automated Diagnostics: Field Test Results" paper. (PDF 508KB)