Figure 1: Tempered chilled Water system, annotated Altitude (BMS) user interface

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1 Abstract: In Spring quarter 2012, we explored the Y2E2 tempered chilled water system functionality, associated Sequence of Operations (SOO) scripts, and previously gathered results as illustrated in the Data Manual. Our intent in the study was to understand the behavior of the tempered chilled water system holistically, with all TCHWS SOO rules in tandem during all major identified demand situations. The system behavior was analyzed by creating time series graphs, scatter plots and carpet diagrams directly in the SEE-IT system, and by outputting time series information to excel, then analyzing Sequence of Operations prescribed system behavior via excel logic rules. Using our knowledge of the system s intended behavior, we identified typical operating situations for differing ambient conditions throughout the year, searched for appropriate data moments to base our analysis, and subsequently ran one minute interval sensor information for each one week data moment. The minute-by-minute values were exported to excel CSV files, the data time aligned and all SOO rules applied via excel logic statements. After reviewing the excel results, follow up analysis was performed to bolster initial results. Results indicate the system mostly performs as intended. The pumps operate on a different sequence of operations than described, so it was not possible to verify all the rules. However, we confirmed the weekly lead-lag switching of the two pumps, and verified that the dew point reset works well. The supply temperature conformance to the set point appears very well behaved. System operators should be pleased to find out that the TCHW system is working well. Annotated Tempered Chilled Water System diagram Figure 1: Tempered chilled Water system, annotated Altitude (BMS) user interface 1

2 Editable Point List The following chart summarizes our exploration of the TCHWS points, ranges and historical observations. Rows shown in light blue at the top of the list are the points reviewed relative to the Sequence of operations and excel analysis. Pink highlighted points appear to be duplicates in the system. For an editable version including tour updated information see the excel file named Y2E2 point list-tchw. TCHW System Points: (See excel file named Y2E2 point list-tchw for editable version) Figure 2: TCHWS point list showing known operating parameters and spring 2012 findings Analysis Approach: Using the previously determined analysis steps shown in figure 3 as a starting point, we adapted the method to examining a system over all major operating modes. Essentially, when examining an entire system, major operating modes and behaviors need to be identified and SEE-IT graphs iterated to be sure to capture all interactions between system components. The points graphed should be inclusive of enough points to completely describe behavior, but limited to only essential points, as excess data can make analysis much more difficult. 2

3 1. Select System (TCHW) 2. Read SOO & Data Manual Y2E2 Tempered Chilled Water System Functionality Linda Brown 3. Functionalize described behavior using: Diagrams in Altitude and Y2E2 Data Manual Current understanding of building and system Discussion with professor, building manager and peers 4. Determine system points (SEE-IT) 5. Observe SEE IT data over Months and Years 6. Find data moments capturing system modes When rule is clearly active or inactive Seasons (affecting outdoor temperature/dew point and therefore system behavior) Interesting data behavior Other factors 7. Run one minute time series, export to excel, pivot 8. Create and Apply excel functionalized rules 9. Analyze results 10. Apply other statistical methods where needed 11. Use narratives, Diagrams, and Graphs to share results Once the tempered chilled water system was selected, we initially reviewed system references and had discussions with teaching team and building operators. Using system sensor points, we applied SEE IT software to explore system behavior Figure 3: Tobias Maile et al analysis method modes using 60 minute time intervals over long time periods (months to years). Based on the visual results and the Sequence of Operations intent, we reviewed SEE-IT runs for representative data moments that captured the system operating behaviors well, as well as any obviously anomalous behavior. The following representative time windows were chosen because they capture the system s major behavior modes well: 1. Tempered chilled water system during heavy use, such as summer months, illustrated by June 2011 data; 2. Tempered Chilled water system with lower use, such as winter months with low outdoor ambient temperatures, illustrated by January 2012 data; and 3. A period when the outdoor dew point temperature is above the normal system set point for an extended time, illustrated by August 2011 data. For each representative one week time window, one minute values were used to generate excel Data used for further analysis. 3

4 DATA moment descriptions and graphic representations Data moment One- High system demand with low dew point Figure 4: 2011 SEE-IT for a portion of sensors in the tempered chilled water system For our initial data runs, we tried different combinations of sensor points from the tempered chilled water systems and from external systems, such as the outdoor temperature, the dew point temperature, and representative interior space temps. Figure 4 represents one of our one year runs with sufficient data to apply most of the system rules. It is apparent from this time series that we can tell where the data is continuous, and where we would expect TCWH to be in heavy use. We can also see from this graph that it is difficult to see what the system is actually doing because the graphed lines are too dense even with 60 minutes between data points.based on viewing different sensor configurations over all available historical data and performing many test runs, we determined that june of 2011 did a great job of showing the TCHW system under high use, but with mostly lower outdoor dew point temperatures. The low outside dew point temperatures allowed us to examine the stsem operation under stable conditions, as an elevated dew point causes the valve and differential pressure settings to cycle rapidly. 4

5 Figure 5: June 2011 data for the tempered chilled water system In figure 5, we see the month of June 2011 in close up, and can now discern behavior of components in relation to each other and in relation to external conditions. Based on the attributes of interaction during the week of June first to the eighth, we used this time frame to create minute by minute readings for all necessary sensor data. 5

6 Figure 6: June data for the tempered chilled water system In figure 6, we can see an extreme close up of system behavior during the week on June 1-8, showing the outdoor temperature diurnal behavior, the dew point and response, the valve behavior connecting the system the the chilled water system. As the outdoor temperature rises, the valve behavior changes. The valve and system set point also change during elevated dew point time periods, and return to their patterns when the dew point goes below the supply set point. 6

7 Data Moment Two- Low system demand Data Moment number two was chosen to best represent the system during low demand periods, with lower overnight and overall ambient temperatures, and associated low demand system behavior. Once again, we reviewed different sensor combinations over long periods, magnified data month by month and week by week, until a defendable representative time period became apparent. Figure 7: January 2012 SEE-IT for the tempered chilled water system Figure 7 shows the month of January 2012, where we found periods of low ambient and overnight temperature, periods of regular diunal response pattens for the system, and a week with several rises and resets of dew point and associated system responses. 7

8 Figure 8: January data for the tempered chilled water system To capture the low system demand resonse the week of january 18 th -26 th 2012 was chosen, as it had a combination of regular diurnal system behavior with several dew point elevation and reset actions. See figure 8 for SEE-IT representation of the week. Data Moment Three: heavy demand, extended dew point elevation During spring summer and fall months, the local weather pattern shows a predilection toward extended periods with elevated dew point temperature. As shown in figure 9, we determined that this major behavior mode was well represented by August of Figure 9: August 2011 SEE-IT graph for the tempered chilled water system 8

9 August of 2011 is a good representative of the high demand, high dew point condition, as shown in figure 9. From figure 10 below, we can see the one week period reflecting the condition and the system behavior well. Figure 10: August SEE-IT for the tempered chilled water system 9

10 Tempered Chilled Water Analysis Starting with the sequence of operations, we broke down the sections, numbered them for ease of tracking and verified and tested the system behavior against the SOO rules.figure 11 show the rules, our numbering of the rules and our test and verification high level results. The following section aligns functional intent, points, rules, and analysis examples for each rule. Figure 11: SOO rules verification and test status 10

11 SOO Rule #0: Tempered chilled water system description : SOO statement: The tempered chilled water loop consists of two basemounted end-suction pumps located in the mechanical room. These pumps circulate water through a closed loop that feeds the active chilled beams throughout the building. Functional intent: Describe the system. The Tempered chilled Water system is a set of pumps and piping that connects externally to the district wide Chilled water system, and on the building side to Chilled beams only. System diagram: See figure one Assumptions: Altitude system is correct, beams are the only item serviced by the system System points: see figure two, all points are part of the system Operationalized rules: none. Excel operationalized rules: none. Examples of data and assessments and statistics: Visual verification of system existence suffices. DATA manual update: Consider adding text to describe the external connection via the system return to the district wide chilled water loop. Rule performance trends and conclusions: none Figure 12: Y2E2 system components document piping section for TCHW system SOO RULE #1: Pump On/Off and Speed Control SOO statement: Rule 1: CHWP-B2 and CHWP-B3 shall be controlled through the building management system (BMS). System on/off and lead/lag position will be through a weekly schedule programmed into the BMS. Functional intent: The pumps are to be controlled by the BMS The leading pump designation shall be alternated weekly, to keep even wear on each pump. Operationalized Rules: No operationalized rules are necessary-visual inspection confirms that the pumps are controlled by the BMS and are reported by several sensors each. See figure 13 for pump behavior since system reporting began Excel Operationalized rule: SEE -IT charts confirms that the pumps are mostly used for 50 % of time each, therefore an excel analysis is not needed. If an excel analysis was run, the analysis would measure pump status percentages for points 11

12 & pump status pumps 2 and 3, and see how close to 50% each they are. Figure 13: pump data for 3.5 years Figure 14: pump data from

13 What are the pumps doing now? Figure 15: pump data from 5/1/09 to 5/1/10 Figure 16: pump data from

14 Figure 17: pump data from 5/1/11 to 5/15/11 Strengths and weaknesses of graphic representation 1. We learned that scale is very important and different data types require different scales of analysis, especially scripts that involve short time frames. 2. When showing graphs it is best to show a small number of variables and keep the graph uncluttered. a. Similarly, it is important not to clutter graphs with annotations to the point that you cover up relevant data. 3. Excel is a great way to assess data, but the tables aren t always the best ways of conveying results to others. Graphs are much clearer for an unfamiliar audience. Guidelines for Best Practices for Status Classification and Representing System Data!!! 1. It is best to represent system data in consistent colors. This is sometimes difficult with SEE IT graphs, but presenting multiple graphs where one variable has a variety of colors makes it difficult to assess data status classification quickly. 2. It is important to choose an appropriate time period for assessment and data representation. For example, the graph above shows some data clearly, such as the pump on/off status, and some data poorly, such as the squiggly blue and green pressure and temperature data. To better understand this data, we found ourselves looking at week-long intervals for clearer data assessment. 3. Stop-lights or smiley faces? A difficult question. 14

15 SOO RULE #2: Pump staging behavior under increased differential pressure SOO Statement: When tempered chilled water is required, the lead pump shall be staged on. If the lead pump cannot maintain the differential pressure setpoint for 5 min (adj), the lag pump shall be started. Both pumps shall ramp up to their maximum speed and then ramp down together to maintain the differential pressure setpoint Assumptions: none 15

16 Examples of data and assessments and statistics: Visual verification in SEE-IT confirms that the VFD frequency is a tracked sensor point. The BMS altitude shows the pump frequency, see figure one. Also see figures below. Figure 18: Pump data for the month of June 2011 Figure 19: Pump data for the week of June

17 Figure 20: rule 2 conformance test excel screen shot Rule performance trends and conclusions: the IF part of rule 2 was tested and the differential pressure exceeded the set point but nothing occurred. This is due t the fact that the pumps are oversized, we are told by the Building managers. See figure 18 and the excel file. SOO Rule 3: VFDs control differential Setpoint The BMS shall maintain the differential setpoint by controlling the speed of the VFD s. The differential setpoint shall be adjustable through the BMS and set during the test and balance of the tempered chilled water system. Functional intent: the intent is to describe how the pumps will be controlled. Pumps are more efficient when controlled via variable frequency drive (rather than valves) and the SOO writer wanted to make sure this happened. The differential pressure needs to be easily adjustable to balance the system at commissioning and later when system parts change. Operationalizing rules: none Excel operationalized rule: none Examples of data and assessments and statistics: Visual verification in SEE-IT confirms that the VFD frequency is a tracked sensor point. The BMS altitude shows the pump frequency, see figure one. Rule performance trends and conclusions: no trends and conclusions to report on this rule. 17

18 SOO RULE #4 SOO statement: When both pumps are running, if they are running below 25 Hz for a period of 5 min (adj) then the lag pump shall be staged off. Both pumps shall be staged off during unoccupied hours. If a thermostat override is activated within the building and there is a call for cooling in that zone, the lead pump shall be enabled Assumptions: none Examples of data and assessments and statistics: like rule 2, Visual verification SEE-IT graphs confirms that the pumps are never on at the same time. See figures in Rule 2 for comments on data. Rule performance trends and conclusions: Like Rule 2, this situation never happens, we have been informed that the pumps are oversized from the original plan, and are now 100% redundant. Figure 21: Overall Pump Rules Conformance 18

19 SOO RULE#5: Temperature Control - Normal Operation SOO statement: The tempered chilled water supply shall be maintained at a temperature of 60 F (adj). A control valve in the line returning water to the building chilled water system will be used to maintain the setpoint. When the tempered chilled water supply temperature rises above 60 F the control valve shall modulate open. When the tempered chilled water supply drops below 60 F the control valve shall modulate closed. On loss of power the control valve shall fail closed. Assumptions: Since there is no information on range or time, we used 1 degree and three degree intervals and assumed a five minute look back and reaction time. Examples of data and assessments and statistics: Rule performance trends and conclusions: Figure 22: Overall Rule 5 Conformance 19

20 SOO Rule #6 & Rule #7: Supply Temperature Reset SOO statement: In order to ensure that water does not condense on the active chilled beam, the tempered chilled water may need to be reset. The BMS shall monitor the outside air dewpoint. If the dewpoint of the outside air rises above 58 F (adj.) for a period of 5 minutes (adj.) the tempered chilled water supply setpoint shall be reset to stay 2 F above the dewpoint. If the outside air dewpoint drops below 58 F (adj.) for a period of 5 minutes (adj.) the tempered chilled water supply setpoint shall revert back to normal control. Rule # 6 Rule # 7 20

21 Assumptions: Rules #6 and #7were assessed in tandem. The difference we used to asses was 1.8 degrees as the 2 degree rule never was met. Also, the 58 degree change setting was changed to 53 degrees as the set point is 55 degrees. Examples of data and assessments and statistics: Figure 23: Screen Shot of excel assessment of rule 6 and 7 conformance In figure?, a screen shot of the excel used to asses rule 6 and 7 performance is shown. Minute By minute SEE-IT data from the three different weeks was exported to excel, pivoted, rules applied, then performance was assessed. The excel results showed that rule six and seven conformed the bulk of the time- with a nonconformance of around 3%. While this tells us something about the conformance, in the case of dew point rise and supply temp we thought that a scatter plot would be a better assessment of behavior relative to intent: 21

22 Figure 24: scatter plot of one and a half years of supply temp versus dew point temp Rule performance trends and conclusions: As we can see from figure? the bulk of the scatter point conform very well to the intent. The supply temp is well grouped around 55 degrees (normal set point temp0 until the outdoor dew point gets to 53 degrees, then the two rise in tandem. There are a few points not in the trend areas, but they may be errors in data. Impact to system operators for rule 6 and 7: System operators will be relieved to know that the dew point response is working very well, which is bolstered by the fact that no building occupant has reported chilled beam drips or rain. Rule performance trends and conclusions: 22

23 Data Manual Update Y2E2 Tempered Chilled Water System Functionality Linda Brown (2 points) Describe your system clearly and submit (in Word format): o Show a systems diagram; (see earlier section) o List specific BMS sample and control points (see system diagram above and point list provided in Excel.) o Describe the system functional intent, typically a copy of the intent from the Sequence of Operations that you might edit to reflect any updated understanding; See tables above with sections of SOO (1 point) The current point description tables in the Data Manual typically are uneditable.jpg images. Please create and submit editable Excel point description tables: o Include all columns in the point list table (see source 2 in Background) in your Wiki table. As it may be helpful, please edit or add comments to column names to maximize precision and clarity For your convenience and the convenience of readers, please order values in the data table so that your six or so parameters appear close to each other in the table and other parameter rows are above or below your reference point rows. Done. We believe the data manual should adopt the point list table with point IDs rather than the vague un-editable tables now in place. o Add a column to your point list table to describe an additional useful property; Historical observations o For the BMS sample points referenced in your operationalized rules or at least six points, add values for point attribute values, based on you have learned from other sources such as the Sequence of Operations or inferred by looking at data or appealing to engineering judgment. Done (1 point) Add a Guide for users page to your wiki that explains how to (maximum 250 words): o Explain how the diagnostic process you followed can be used more generally to interpret data over time for Y2E2 and other buildings with a computer-based energy building management system; We described our diagnostic/analytic process in an earlier section and in our slides. For students this process can be used to verify building system behavior over long time periods. Rules can be combined to determine what parts of systems are least conforming, and could potentially be combined with energy information to understand building inefficiencies. In Y2E2, one of the shortcomings is lack of documentation about changes to the Sequence over time, which makes historical tracking of system conformance difficult. We see an opportunity for the system to self-test. We have established crude Excel-based rules based on the SOO. The improved method would be to write self-testing code into the system that tested whether the operators building rules had the intended functionality. o Choose where to spend time to improve building energy use. 23

24 Our data assessment shows that most of the TCHW system works as intended. There may be more efficient ways to size and run the pumps, but other than that other building systems would be better targets for energy improvements. Hydronic systems tend to be more efficient in general. The air side of the system would probably be a more effective area to focus on. Resolving ambiguities Error in the Current Data Manual Tempered Chilled Water Loop "Aside from the fact that the tempered hot water loop in Y2E2 has a supply temperature set point and the tempered chilled water loop does not..." I don't believe this is accurate. There is a data point in SEE IT (#1195) for the tempered chilled water supply temp set point that we have been using all quarter to test our functional intent rules. The default set point appears to be 55 degrees Fahrenheit unless affected by dew point or other rules. The tempered hot water loop supply temp set point is #1211. The tempered cold water loop supply temp set point is #1195. Valve Position Data Values In General Valve Positions represented by a range of 0 to 1 or 0 to 100% vary in whether "0" represents Open or Closed. There is a Valve Schedule showing some details such as whether a valve is "normally closed" (NC), but that is not correlated with the 1 or 0 value. (Source: Tim Troxell) Tempered Chilled Water The valve in this system is Normally Closed according to the Valve Schedule, with higher values representing a more open position.* Values in SEE IT and Altitude are not in the same units. Altitude shows a range of 2 to 10; SEE-IT shows this range multiplied by 10: 20 to 100. Therefore, this is not strictly a "percent closed" value and would need to be converted to a range..*according to Tim Troxell. Data indicating the inverse relationship was presented in the slides (and shown below) but did not receive a response. 24

25 Figure 25: Note to Building Operators is this valve normally open or closed, based on the chart above? Figure 26: Valve position, one week in June The figure above shows the behavior of the valve position alongside outdoor air temp, supply temp and supply air flow. There is still confusion about the meaning of data values for this valve, despite various analyses and discussions with appropriate people. 25

26 Atrium Naming Conventions Names for Atriums varied by data source and were not clearly correlated. Below are our observations: Altitude Sequence of Operations Other Naming Location Color System A 1 (1 & 2 Grouped North Red B 2 for some operations) Packard West Blue C 3 (3 & 4 Grouped Precourt Center Yellow D 4 for some operations) East Green ORID Analysis (for the Quarter) Objective Claire- I feel I have learned some things about typical v. desirable facilities management and control systems. Linda- I have gained perspective on the BMS system as deployed in Y2E2. I have also gained mechanical system knowledge of chilled beam usage and stack night flush. Reflective Claire- I am discouraged about the state of the practice of energy management and building data analysis. Linda- I am surprised and frustrated that a 'predicting building energy' class at Stanford has so little content associated with 'energy' or 'prediction', as I expressly asked if this would be covered in the class, and was told that it would. Interpretive Claire- I have a better sense of several things that need to be in order before data can become useful to a building manager or a student. Linda- Sense = Frustration. I do not agree with the major theme of the class, which is: "energy prediction can't be done". It would have been helpful to explore the BMS in conjunction with actual energy use and add context of various prediction and energy use improvement models. If the class is about optimizing building performance, we could have explored continuous commissioning or automated building optimization ideas. If the class is about energy analysis, we could have explored Y2E2 energy use and compared it to other buildings on campus using other systems to heat and cool. If the class is about prediction we could have looked at predicted data derived in various manners, as there are many in use. 26

27 Decisional Y2E2 Tempered Chilled Water System Functionality Linda Brown Claire- I will find outside reading for the summer about efforts toward thorough building energy analysis. Linda- explore other emerging work in tying predicted behavior models to actual buildings and to Ideas meant to lower FM energy usage. Specifically, I am interested to see how the Packard center net zero deployment in Los Altos progresses, and what their FM attitude and behavior is. I aslo hope to gather information from GSA net zero deployments and contribute to the Knowledge of best practices in lowering energy use in FM in general. 27