Single-Source Solutions: Proactive Building Automation Systems
First observation when reviewing the existing bas installation:
- System graphics were included but without any sequence of operation on the bas monitor. As a result, when asking a question relative to the graphic on the screen, the facility person did not have the answer because he didn't have a copy of the system narrative available for reference. Solution: Have the ability to simultaneously show the sequence of operation and the system flow diagram on the computer monitor.
- Actual performance criteria exceeded the cfm design data noted on the bas graphic. Again, the facility person did not have an answer to the question of why the performance was (in this case) approximately 15% in excess of graphic data. Solution: Have an "alarm" designation, flashing on and off with a warning that energy consumption (in this example) is 15% over design intent. In addition, the alarm should provide direction as to what to do next.
Second observation was that pertinent system data was capable of being monitored but no monitoring had been included in the bas software:
- The bas operator was capable of reading the filter pressure drop. Had the software been set up to be proactive, this costly data point could have been better used to predict when the filter should be changed. Without predictive maintenance capabilities, a "read-only" setpoint offers little value to a facility manager. Solution: Include a predictive maintenance "alarm" designation, flashing on and off, forewarning of a pending filter change. In addition, the alarm should provide direction as to what to do next.
- Actual duct static pressure (located three-fourths of the distance downstream of the supply fan) was in excess of design criteria and the bas operator did not realize and/or understand what this meant in excessive operating cost. Designating a system performance setpoint and then not having the bas operator knowledgeable as to the duct static pressure control concept will result in wasted fan horsepower/energy. Solution: Train the bas operator in design intent more thoroughly. Also consider a more progressive method of duct static pressure control by applying discriminator control so that the direct digitally controlled air terminals can determine the air valve needing maximum duct system pressure to maintain the minimum cfm through the terminal.
Third observation was that no trending information had been included in the bas software:
- It isn't unusual for an air-handling system to have 15, 20, maybe 30 data points but what is unusual is application of the control strategy that will use many of these points for trending purposes.
- An example of proactive trending is to record simultaneously the sequencing of heating and cooling control valves opening and closing. Through a form of trending, the bas operator can routinely monitor these two valves to make sure they do not go out of synchronization, resulting in both valves being open at the same time.
- Trending the energy consumed by an air-handling unit along with real-time weather data and simultaneously comparing this consumption with design intent performance via an energy profile can possibly identify energy waste as it is happening.
A common practice with bas software is to incorporate setpoints, transmission signals, flow measuring stations, and high- and low-limit alarms that, over time, can go unchecked and eventually ignored. Through predictive and proactive measuring, trending, and management alarms, bas software can be developed to contribute to a positive management process and assist in "driving" building management. ES