February 2, 2018
How Building Systems Can Function at Peak Efficiency with Fault Detection and Diagnostics Analytics
By Edison Energy
There’s a fault occurring in the building systems. It can run virtually undetected because you may not know it’s even there. And no matter how much you invest in building automation systems (BAS) and energy-efficient equipment, your BAS won’t minimize overall energy usage if not properly optimized and maintained. The key is marrying the BAS with fault detection, diagnostics and optimization analytics (FDD).
A building automation system (BAS), also known as a building management system, is typically installed in larger buildings to control and monitor mechanical and electrical equipment, such as heating, ventilation and air conditioning (HVAC), lighting, power systems (meters), fire systems, and security systems.
A BAS uses algorithms programmed by the vendor to provide occupant comfort, efficient operation of building systems, and reduction in energy consumption and operating costs. But those algorithms go only so far.
Fault Detection, Diagnostics, and Optimization
While a BAS has alarms for temperature or failed equipment at a single point, fault detection and diagnostics and optimization software drives to a much deeper level of analysis of a system and determines root cause faults.
FDD platforms automate the process of detecting faults with physical systems and processes and diagnoses their potential causes. FDD systems for HVAC generally use a database of fault rules that analyze BAS and meter data to determine fault conditions. Here’s how FDDs programs can root out the most common BAS optimization faults:
When a building automation system is first commissioned, an operating schedule is programmed in for each piece of equipment or system. However, buildings have constantly changing schedules and temperature requests. A typical university or office will modify the schedule according to the requirements of the space. That request may be for only one day, but it may continue to stay in that override condition without FDD. As a result, the air handling unit (AHU) serving the space may be using significantly more energy than prior to that day, yet no one has found that fault because there are no alarms to monitor.
2. Air Change per Hour (ACH) reduction in zones
Environmental Health and Safety (EH&S) officers oversee providing a safe building environment. EH&S officers follow industry guidelines and standards. However, as the standards have changed and FDD has become available, the air change per hour (ACH) rates in buildings have not been lowered as quickly. Reducing ACH rates by 25 percent provides a 25 percent savings in heating and cooling and a reduction in fan energy as well. For each zone in a building that is receiving 1,000 cubic feet per minute (CFM) of 100 percent outside air that is a savings of approximately $1,000/yr.
3. Economizers not operating correctly
Today’s complex systems are designed with modulating amounts of outside air based on return and outside air conditions. Advanced systems also monitor CO2 levels. A properly designed and operated economizer cycle — a system of dampers, temperature and humidity sensors, and actuators — maximizes the use of outdoor air for cooling and heating. If an outside air damper is 100 percent open when the outside air is below 32 F, there is potential for frozen coils and added costs for facility personnel. If the outside air damper is 100 percent open when the OA is above 90F, the cooling coil may be signaled at maximum cooling capacity but not be able to provide adequate cooling.
This not only results in additional cooling energy wasted, but also comfort complaints. In the case of spaces that require humidity control, this may result in damage to things like rare library books, operating rooms that are not useable, and validated pharmaceuticals that are forced to shut down processes.
4. Equipment Proportional-Integral-Derivative (PID) loop cycling issues
HVAC and process equipment may be constantly modulating to maintain setpoint conditions. However, how often is the PID loop cycling every fifteen minutes? How much of a deadband is programmed into the sequence of operation (SOO). Equipment than isn’t programmed correctly can lead to premature failure, resulting in additional increases in equipment costs and failures at the worst times. FDD allows for analyzing control loops and identifying which ones need to be tuned before equipment fails.
Virtual Energy Management (VEM)
Virtual Energy Management (VEM) is Edison Energy’s Continuous Commissioning or FDD Process. VEM Monitoring provides a continuous source of time-series building data. VEM Analytics provides for discovery, interpretation and communication of meaningful patterns in the data. VEM brings together energy and BAS data to provide instant insights into faults and optimization opportunities.
The following figure shows the sustainability results of implementing VEM over time. Energy consumption stabilizes and decreases beyond a new baseline through continuous optimization.
VEM Sustained Results
What’s next with Building Automation System Optimization
As the internet of things (IOT) continues to grow and wireless sensors become more plentiful in buildings, FDD platforms will be able to do more with the data available.
In addition, although most FDD platforms currently only identify faults and optimization opportunities, the next step in the evolution of FDD will be to actively optimize operations, going to machine logic that will automatically update software algorithms to self-correct and self-optimize on an ongoing basis.
This combined with renewables, battery technology, and microgrids will drive buildings towards net zero. There will need to be more FDD in the near future to meet energy targets and persistence of energy savings.