Alameda County Courthouse
This demonstration of the Whole-Building Diagnostician (WBD), documents the online analysis of data for the multi-building operator demonstration being conducted at Alameda County buildings. Battelle working with Newport Design Consultants implemented the online test configuration, data collection, data analysis, and documentation for this demonstration. The online test was designed to evaluate the Outdoor-Air Economizer (OAE) diagnostic module’s capabilities to automatically and continually diagnose operational problems with air handling units (AHU’s).
The multiple-building operator demonstration took place at the County of Alameda GSA Tech Services County Offices facilities using the buildings listed in Table 1. The County of Alameda currently owns or leases approximately 120 buildings consisting of 6.2 million square feet of owned office space and 1.1 million square feet of leased office space. Among those buildings are a jail, a number of courthouses, clinics, office buildings and juvenile halls. Our demonstration sites, listed in the table below, consist of 2 courthouses and 2 emergency buildings. These buildings were selected for the following reasons:
- They are the most important buildings to Alameda Country
- They have been upgraded to the latest Control Systems International (CSI) control system
- They have central data archives
- They are suitable for the OAE diagnostician because they have mostly relatively large air handlers servicing the buildings.
WBD Results
Alameda County Building in the Demonstration| Building | Air-Handling Units | Square Footage |
| Alameda County Courthouse / Wiley W. Manuel Courthouse (OPMC) | 2 | 210,400 |
| Hayward Hall of Justice (HHOJ) | 2 | 191,300 |
| Office of Emergency Services (OES) | 3 - packaged | 14,200 |
| Emergency Operations Center (EOC) | 1 | 20,000 |
The building’s HVAC (heating, ventilating and air-conditioning) consists of hydronic systems with centrifugal chillers, and natural gas hydronic boilers. Four large variable-air-volume (VAV) air handlers with heating and cooling coils, differential dry-bulb controlled economizers and variable speed drives (see table below), serve the occupied space. A direct digital control (DDC) system from CSI controls the HVAC systems, which also provides a mechanism for trend logs.
| Air-Handler | Rated Flow (ft3/min) |
|
| HHOJ AHU S-1 | 90,500 | |
| HHOJ AHU S-2 | 98,750 | |
| OPMC AHU S-1 | 103,750 | |
| OPMC AHU S-2 | 87,160 |
As part of this online demonstration, two AHU’s at the Hayward Hall of Justice (HHOJ), two AHU’s at the Alameda County Courthouse (OPMC), three AHU’s at the Office of Emergency Services (OES) and one AHU at the Emergency Operation Center (EOC) 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) outdoor-air relative humidity, 8) return-air relative humidity 9) hot water valve position 10) supply air set point 11) mixed-air set point and 12) economizer damper position.
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 AHU’s was automatically collected using trend log data 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 Alameda County, 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 February of 2001 at the OPMC AHU’s and November of 2002 at the HHOJ AHU’s. The three packaged AHU’s at the OES building were dropped from the on-line analysis because they did not have all the necessary data points to perform the diagnostics. Because the units were packaged direct-expansion units, the heating and cooling modes were not directly accessible through the building automation system. The AHU’s at the EOC building lacked return-air temperature, which is a critical input required for diagnostics; therefore, it was dropped as well. Due to a number of problems with the data collection, a number of gaps in the data were encountered.
All four AHU’s at Alameda County had outstanding problems. The predominant problem for each of the four AHU’s with corresponding energy cost impact for the demonstration period are: 1) HHOJ AHU S-1 had the damper not fully opening during economizer operations with an energy cost impact $1,800, 2) HHOJ AHU S-2 had the damper not fully opening during economizer operations with an energy cost impact $300, 3) OPMC AHU S-1 had the damper not fully opening during economizer operations with an energy cost impact $15,750 and 4) OPMC AHU S-2 had the damper not fully opening during economizer operations with an energy cost impact $10,000.
The energy project manager for Alameda County indicated that the WBD tool set was useful and added that he would like more diagnostic tools such as WBD for other HVAC systems. He also reported that the user interface for both the WBD and the OAE diagnostician where easy to use with the exception of data collection. Although the OAE diagnostician has identified a number of problems, the site administrator and operators addressed only one problem.
The OAE diagnostician was shown to successfully identify problems with all four AHU’s at Alameda County. These findings are consistent with the other field demonstrations of the WBD where 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)