*4.2. Incorporate Operator Approval*

The second challenge faced by the partners was incorporating operator approval. The new auto-correction feature affords the FDD technology a certain degree of control capability. The building operators may be hesitant to trust this new capability and feel a lack of control. To mitigate this challenge, one project partner updated the existing interface to make sure the users were allowed to actively start, interrupt and track the auto-correction activities. Auto-correction enable and disable functionality was added to the user interface (UI), and the name of the control variables, their current value, and the new proposed values were provided to increase the operators' awareness. All the user and system activities of auto-correction are stored in a history log that is available to the user. Figure 10 shows a simplified mockup of the new UI displaying the auto-correction enable/disable functionality, action history and other details. Another partner also developed new interfaces for auto-correction authentication and acknowledgement.


**Figure 10.** Mockup of the new user interface (UI) developed by one partner, displaying the auto-correction enable/disable functionality, the action history and other details (ASO – Automatic System Optimization).

#### *4.3. Manage BAS and Site-Specific Customizations*

The traditional separation of the roles between the FDD and the BAS allowed the FDD tools to develop general algorithms that were independent from some of the details about BAS and the implementation of specific control programs. For instance, an algorithm that detects opportunities to save energy by shortening the AHU schedules did not need to know how these schedules were implemented in the BAS, it just needs to analyze the data produced by them. However, auto-correcting the same schedule meant overriding the operation of the BAS, therefore the developers must know many more details about the specific implementation of the control logic to avoid unintended consequences. The third challenge confronted was the lack of standardization in the BAS control logic, variables and interfaces. The implementation partners reported issues in (1) deciphering the BAS control sequences and identifying the exact control variables to override, (2) gaining access to these variables and (3) gathering data with frequency and timeliness appropriate to the application. An example of the first issue is the implementation of the "override manual control" algorithm described in Section 2.2. Depending upon the BAS, the override can be accomplished via an "override" variable Manual\_override (whose value is 1—equipment is in manual control, 0—equipment is in automatic control) or by the setting of the priority level of the BACnet points (e.g., 8—manual operator override, 16—default automatically operation) [27].

Accessing the proper control variable was another part of the challenge. The auto-correction algorithms may require the FDD tools to be able to access the control variables that are not commonly exposed to the outside by the BAS. An example is the PID-tuning parameters required by the "control hunting" algorithm. One implementation partner reported being unable to retrieve these points via BACnet for a site, since the BAS vendor used a proprietary solution. -The third issue emerged when a partner implemented the algorithms described in Section 3. These routines need real-time data updated every few minutes, since the algorithms are reevaluated continuously, while the existing BAS was storing it at 15-minute intervals and transmitting it to the FDD tool once a day (to save memory and bandwidth).

To address the challenges, all the partners had to spend significant time to understand and modify the BAS programming and setup, in addition to its interface with the FDD tool. The parameters of the BAS controller, gateway or server were changed to expose the necessary variables, making sure they could be modified when needed. Sampling frequency and data transfer rate were increased to implement some of the algorithms. A partner created a virtual point in the actual codes to accommodate the settings of override in various BASs. The virtual point is a string semicolon delimited list of point IDs that are mapped to any points that need to be changed from override in the BAS. A partner reported that particular care had to be put into matching appropriate data types (e.g., binary, analog with different precisions, arrays) used by the BACnet protocol, to avoid communication errors. All these customizations varied by BAS vendor, hardware vintage and site configuration.

#### *4.4. Manage Control Conflicts between the BAS and the FDD Tool*

The last challenge reported pertained to the conflicts between the BAS and the FDD control actions. Algorithms that make one-time changes to the BAS operation (e.g., the incorrectly programmed schedule in Section 2.1) may be overridden by operators or the BAS logic at a later date. It is unclear whether or not the auto-correction procedure should periodically update these variables. Moreover, algorithms that continuously change variables may also conflict with the existing BAS sequence of operation. An example is improving the AHU static pressure setpoint reset (Section 2.8) on a BAS that already has a reset strategy. There is a need to understand which one takes precedence and if the existing control sequences should be turned <sup>o</sup>ff.

To address the first issue, one implementation partner used an existing feature of the FDD platform to separately track the active schedule and the most efficient schedule and let the operator decide which one to activate. In addition, it logged all the changes to that schedule to offer more information to the user. For the second issue, another partner set up a fallback mechanism in the BAS, for use with the new FDD auto-correction algorithm that continuously modified the control setpoint. A watchdog was added in the BAS programming to make sure the FDD tool was online. If the FDD tool went offline, the BAS reverted back to the setpoint generated by the original control logic in the case of loss of communication with the FDD tool.
