Optimizing BAS Information for Operator Effectiveness and Optimal Control

Transcription

1 Optimizing BAS Information for Operator Effectiveness and Optimal Control Len Beyea, CBCxP, EBCxP, HBDP, CEM, LEED AP Principal, RetroCom Energy Strategies, Inc. Synopsis Building automation systems have become standard tools for facility operation and monitoring, and commissioning providers use them routinely to gather data and to test system operation. But for O&M staff who are responsible for day-to-day facility operations, the usefulness of a BAS may be limited to simply spotting out-of-range conditions in order to take action before the condition results in a complaint or a breakdown. In most cases the information provided does not facilitate recognition or evaluation of problems, especially in regard to the efficiency of operation or overall system performance. Developing displays that present information in such a way that performance problems can be quickly recognized can make a difference both in how appropriate or effective corrective actions are, and in how engaged operators are in maintaining performance of controlled systems. This paper presents some examples of how building automation system (BAS) displays and overrides can be configured to allow operators to carry out daily responsibilities while protecting the integrity of optimization programs in the BAS. Examples are taken from retrocommissioning work the author is engaged in with Los Rios Community College District, a California community college system with four large campuses and four satellite campuses. About the Author Len Beyea has worked in the field of building energy efficiency since 1980, including as an inhouse energy manager for San Mateo County, an urban county in California s San Francisco Bay Area, as an applications engineer in a controls automation company, and as a project engineer in a cogeneration company. He began developed his commissioning skills working in the Energy Saving Performance Contracting industry, where he was responsible for design and commissioning of building automation systems, central plant renovations, cogeneration systems, VAV conversions, and a wide range of other upgrades in academic, health care, government, and military facilities. In 2006 he co-founded RetroCom Energy Strategies, Inc., a California-based consulting firm that provides commissioning, green building, and energy engineering services. Len has acted as lead commissioning agent for RetroCom on more than fifty projects, both new and existing buildings. His presentation at NCBC 2012 is based on experience with optimization of BAS controls and operator interface for a 3-year retro-commissioning program at Los Rios Community College District in California. Len Beyea: Optimizing BAS Information for Operator Effectiveness and Optimal Control 1

2 This paper draws on significant contributions made by Mike Goodrich, Director, Energy and Utilities, for Los Rios Community College District, and Ted Dahlkamp, Control Systems Designer for Honeywell, as well as the collaboration of additional Facilities staff at LRCCD in updating and improving BAS functions and workstation displays. The author expresses his gratitude for their innovative thinking and hard work. Len Beyea: Optimizing BAS Information for Operator Effectiveness and Optimal Control 2

3 Building Automation Systems in the Real World Building Automation Systems (BAS) are often touted as a solution to everything that ails facility operations and maintenance, and are promoted as an energy-saving measure. However, as with all control devices, the results are entirely dependent on how the devices are used. Even with the best of intentions, BAS will not achieve the intended results or the objectives of the designer if the installation is not fully commissioned. Commissioning must include not only proof of hardware functionality, but also testing and tuning of setpoints and control algorithms. Operators Response to Imperfect BAS Controls No system is perfect, but it is not unreasonable to expect a BAS to at least perform as designed. This implies that the design included sufficient detail to define the sequences of operations for controlled systems and installation standards to ensure the serviceability of the components. In many facilities, this was never the case. Specifications are often limited to a few sentences, or are provided by manufacturers, and controls contractors often do projects in effect as design/build, even on jobs that are otherwise defined as bid & spec. But whatever the source of deficiencies in the as-built condition of a building automation system, building operators are the ones who have to cope with the day-to-day consequences. Building Operators Mission If building operators had a mission statement, it would probably read Minimize complaints from occupants. The day-to-day priorities are generally to maintain comfort and keep systems running. Although more and more organizations have explicit programs to improve efficiency or sustainability, these policies in most cases have not been integrated into O&M procedures. As a result of the duties assigned to O&M staff, they must concentrate their efforts on addressing occupant complaints and keeping systems in working order. Working order does not require that equipment is operating at peak efficiency, or that control strategies designed to improve performance are still in place. So when setpoint parameters do not maintain comfortable conditions, even if only infrequently, an automatic temperature reset function may be placed in operator override and fixed at a known safe value. Similarly, if an optimized start algorithm is in the early phase of self-tuning to actual behavior and a sudden shift in weather causes a morning that is too hot or too cold, optimized start may be abandoned for a manually-entered fixed start time. These are appropriate responses at the time, but what we find in most buildings is that temporary overrides become permanent. Further adding to the problem is that in most projects we encounter, automatic programs that were intended to provide improved performance were never tested, tuned or properly commissioned. When this is the case, over time, virtually every program with the complexity to address a wide range of conditions experiences at least one circumstance where served spaces are not sufficiently comfortable, so that the program is overridden and the automatic features are gradually all replaced with operator-entered values. The operators are doing their job, but in so doing have negated the objectives of the BAS for saving energy or reducing loads on equipment. Len Beyea: Optimizing BAS Information for Operator Effectiveness and Optimal Control 3

4 What Works? Everyone involved in the mechanical contracting, building management or commissioning business has seen the graphic screens that have become standard for building automation systems, depicting equipment with values displayed for the various ins and outs and component functions, like those in Figure 1 below. Fig. 1: Typical BAS Air Handler Graphic But do these graphics, as colorful and even visually compelling as some of them are, really convey what operators need to know? Do they enable them to efficiently maintain both the equipment and the control system? At Los Rios Community College District (LRCCD), HVAC technicians who maintain the systems were asked what they needed most in system information, and working with Mike Goodrich, the Director of Energy and Utilities for the District, came up with tables like that shown in Figure 2, below: Len Beyea: Optimizing BAS Information for Operator Effectiveness and Optimal Control 4

5 Fig. 2: Folsom Lake College Air Handler Mode Summary Some of the terms in this AHU Mode Summary bear explanation, which we will address later. But some key elements are visible immediately: Critical data about all units is displayed on as few pages as possible (in this case, one page) Parameters included are not just those that would indicate equipment breakdown or comfort problems, but also those parameters that indicate if optimization programs are working. For example, both setpoints and temperatures are displayed for supply air temperature and static pressure, indicating if controls are maintaining setpoints. In addition, minimum and maximum zone temperatures and terminal load (a numeric value indicating zone demand for cooling or heating) is shown as well, which provides important feedback to determine if operating status and setpoints are appropriate to space conditions. Outside air temperature provides a reality check against heating and cooling modes. Override status is readily determined. In this case there is the possibility of occupant overrides to turn equipment on when scheduled off, as well as security system overrides to turn equipment off when scheduled on. Operators can now see this information immediately, and determine if operating status is appropriate, or if overrides were activated at an appropriate time. Len Beyea: Optimizing BAS Information for Operator Effectiveness and Optimal Control 5

6 If the air handler tag at the left is clicked, it links to the (pre-existing) air handler graphic with more detailed information, which in turn has links to zone terminal box summaries and individual VAV box graphics with detailed zone information, as well as to the central plant. A VAV box summary is shown in Figure 3. Fig. 3: Typical VAV Box Summary for One Air Handler The displays for this particular organization are not necessarily the ones you would use on every project. The display contents have been developed at the same time that optimization strategies were being rolled out at each campus. Operators were educated about what the intended strategies were, and then actively participated in the process of developing display contents to make the project a success. Once the basic principles and objectives were explained, the question posed was What do you need to see to work with this program? As an open-ended question, this discussion lasted through several weekly meetings. Even after the input was incorporated into creation of new displays, additional modifications were proposed over succeeding months as experience was gained in using the system. As a continuous process, the information format is subject to further change. Even the display included in Figure 2 is not complete yet, as run hour logging and CO 2 monitoring will soon be added to the rest of the air handlers. Overrides Operators need the ability to override control outputs. Reasons that operators need override authority include the following: Unscheduled activities Unusually high heating, cooling or ventilation loads, such as occur with special events, leased use of space, etc. Len Beyea: Optimizing BAS Information for Operator Effectiveness and Optimal Control 6

7 Malfunctioning sensors Malfunctioning equipment or components Untested programming parameters causing comfort or equipment maintenance problems Using override functions is not in itself a problem. The problem that occurs in most facilities is that these overrides are often forgotten and may remain in manual mode for weeks, months, or even years. Most BAS software has the capability to clear overrides, but this function is not often used. In the case of LRCCD, where operators were brought in to the dialog about how to address both the need for overrides and the objective of maintaining optimization programs, operators suggested that overrides be swept every Tuesday at noon. That way, if something had been in override but the conditions that motivated the original override had still not been addressed, the condition would be caught during work hours and the override can be re-initiated, program modified, or repair made as required early in the week during regular work hours, before a serious problem had time to develop. In addition, overrides have hierarchies that need to be addressed in the BAS programming. For example, should certain automatic control functions have the effect of cancelling an override, or should override authority be limited to only certain parameters? Should only certain people be able to initiate overrides, and at what level of priority? And what control programs take precedence if there is a conflict between programs? In considering these issues in their own facilities, the Facilities staff of LRCCD came up with the following override hierarchy for air handlers: Len Beyea: Optimizing BAS Information for Operator Effectiveness and Optimal Control 7

8 Fig. 4: LRCCD Override Table (part) The level of detail here underscores the potential complexity of microprocessor controls for any system, and the level of planning that should go into every BAS project. The limits to what can be overridden, by whom, and for how long, what program functions take priority (since overrides are themselves a program function) are all potentially significant issues that should be addressed in design and commissioning of controls. Len Beyea: Optimizing BAS Information for Operator Effectiveness and Optimal Control 8

9 Operator Collaboration for Optimization Strategies Building automation systems offer the potential for complex control strategies to optimize automatic control for every anticipated operating condition. Many strategies commonly implemented with direct digital control (DDC) were not even possible, let alone common, with older pneumatic or electro-mechanical controls. For example, control of economizers used to be limited to one factor, the outside air temperature below which economizer cooling was enabled. This was wired in series with the cooling relay contacts. Minimum ventilation was typically set by a mechanical stop on the damper actuator. With DDC, the program for economizer control can readily include all the following parameters: Economizer enable based on differential between outside air and return air conditions Economizer enable based on differential between outside air temperature and supply air temperature setpoint Modulation of dampers to maintain mixed air or supply air temperature setpoint Enable minimum position control based on occupancy (e.g. no minimum outside air setting during morning warmup or setback temperature control) Variation of minimum position based on airflow reading or fan speed Variation of minimum position based on CO 2 level in conditioned space Override of occupied operation parameters to provide night purge cooling, based on weather history, space temperature, and differential between space temperature and ambient temperature When presented with control strategies of this complexity, building operators first reaction may be to roll their eyes and begin to plot how they can override this inevitably troublesome system and keep it simple. While simplicity has its advantages, reducing energy waste is not one of them. If operators can be engaged in the implementation of optimization strategies, they not only help ensure its persistence, but can also lend insight that makes it possible to succeed. For example, at LRCCD the original strategy for supply air temperature reset based the reset on the maximum VAV box damper position. Operators pointed out that load diversity for several of the air handlers was so high that there was almost always one zone at close to maximum airflow. The program was modified to reset supply air temperature based on the number of zones exceeding cooling setpoint. In addition, the incremental adjustment of setpoints was changed so that supply air would cool off twice as fast as it would warm up, making adaptation to load changes faster, while preserving stability with the same time interval for sample & bump reset. The result of this input resulted in the air handler display changing from that shown in Figure 5 to the diagram in Figure 6. Len Beyea: Optimizing BAS Information for Operator Effectiveness and Optimal Control 9

10 Fig. 5: Folsom Lake College AHU Display Before Operator Input Fig. 6: Folsom Lake College AHU Display After Operator Input Len Beyea: Optimizing BAS Information for Operator Effectiveness and Optimal Control 10

11 An Example The Scheduling Challenge at LRCCD At Los Rios Community College District, as with all academic facilities, one of the biggest challenges they faced was keeping up with changes in schedules of occupancy for all the different spaces on four main campuses and 4 satellite campuses. In the past schedules were set to accommodate the longest operating schedules that occurred in any space. For instructional purposes, this was effectively 8 AM to 10 PM every weekday plus 8:30 AM to 4:30 PM Saturdays. In addition, systems were kept on late at night for custodial crews, because sometimes winter weather can be below freezing, and summer weather, even at night, would sometimes drop from triple digits in the daytime only to the 90s. And of course some time was allowed for morning warm-up or cool-down. As a result, before the optimization of schedules was initiated, most systems operated 6 AM to midnight 5 days a week and approximately 6 AM to 5 PM Saturdays, despite the fact that most spaces were vacant more than half of these scheduled hours. To try to get operating hours under control, first they added information to the academic schedule database used by academic planners for space allocation to show what air handler served each assignable space. This enabled them to go to the academic schedule and quickly discern the occupancy schedule for each air handler, rather than just room-by-room. They began working with the database software provider to devise a software interface to the BAS so that schedules will directly update operating schedules in the BAS this is still in the development. In the meantime, it now takes only about a week to program schedules for a campus, a task that used to take most of the semester, making it impractical except for a few of the largest lecture spaces. Next, they implemented local occupant overrides for each air handler. In some newer areas this was just a program change. In most areas it required changing out at least one thermostat in the zones served by each air handler. Then they met with custodians to explain the override functions and enlist their cooperation in turning off equipment at the end of the classroom schedule, but giving custodians the means to turn equipment on for 2 hours every time they pressed the override buttons on the thermostats, as needed. The same information was communicated to the academic staff. This gave everyone the means to extend space conditioning for late classes, special events, or extreme weather. In practice, custodians are using overrides infrequently, typically only in the coldest or hottest weather. In addition, custodians needed a means to increase ventilation when applying floor finishes, shampooing carpets, etc. For that purpose, a separate override switch was installed in a locked custodial closet in each building that enables custodians not only to bring air handlers on after hours, but increases minimum outside air setting to 50% to dissipate and dry out cleaning fluids when they are used by the custodial staff. The facilities staff at LRCCD implemented one other mechanism to shut off equipment. Each building has a security system that is supposed to be secured by the last person leaving the building. Since classes don t always run to the end of their scheduled time or are occasionally rescheduled or moved off-site, the building is often vacated before the class schedule would indicate. A dry contact from the security system was provided and connected as an input to the Len Beyea: Optimizing BAS Information for Operator Effectiveness and Optimal Control 11

12 BAS. Whenever the security system is armed, operation mode switches from occupied to unoccupied. This has been especially effective in reducing run hours on Fridays and Saturdays. Another Example Operator Notes One of the ideas generated by the dialog with operators was the addition of Operator Notes to each BAS equipment display page. During a conversation going around about who should be told about changes made or overrides initiated, someone asked Well, could we just add that to the display at the operator workstation so we don t have to call Jim every time we make a change? These operator notes are like a log of adjustments made, overrides activated or deactivated, and allow all users to both see what has happened before and record their own activities that affect the control system. The Operator Note link is found on each equipment display page. Following is an example from the Operator Notes for the central chilled water plant at Folsom Lake College: Fig. 7: Folsom Lake College CHW Plant Operator Notes These notes not only provide an easy record of activities, but also enable operators to take informed action to maintain the integrity of the control system functionality. Len Beyea: Optimizing BAS Information for Operator Effectiveness and Optimal Control 12

13 Applying Lessons Learned Having worked as a provider of control systems, as a procurer of control systems and project manager for their installation in ESCO projects, and as a commissioning agent for both new and existing building automation systems, I have argued for years that a complete specification for the BAS is essential to a successful project. Here are the key components of a specification for BAS: Standards for installation, including such things as accessible wiring terminations, wire labeling, where raceway is and is not required, performance of sensors and interface devices, required communication to third-party devices, and configuration of operator workstations and connection options Detailed sequences of operations, including intended control outcomes in every operating mode, control strategies and parameters, alarm limits and delays, software interlocks, and which program parameters are adjustable and by how much Listing of workstation displays Provision of operator training and support documentation Now I will add that it is equally important to review the design with the end users the building operators and to incorporate their input. For new construction, this must be addressed during the commissioning of the system, and can be addressed in the specifications with a statement such as the following: Include summary table displays for air handlers, for all terminal devices served by each air handler, for all chilled water valves, and for all hot water valves, displaying data in tabular format. Summary table contents will be provided following completion of all hardware connections. Equipment listed in each summary table shall link to the respective diagram for the equipment. For existing buildings, operator input can be incorporated right into the design documents. Here are suggested steps to obtain that input: 1. Bring the facility operations team together 2. Describe the types of systems that will be controlled (if new) or review the existing systems that will be controlled 3. Describe the performance objectives, and the control strategies that are planned to achieve those objectives 4. Ask what issues operators anticipate with each automatic control strategy give these some thought and you may be able to contribute to improvements in the operator interface too 5. Ask operators what information they need to know to identify problems this information should be included in summary sheets of systems 6. Ask what operators need to be able to change to address problems, and explore the possible scenarios this is the basis for override parameters and prioritization of authority 7. Ask what else they would like to see in the system Len Beyea: Optimizing BAS Information for Operator Effectiveness and Optimal Control 13

14 8. Take this information and prepare mock-ups of displays and tables or flow charts of override limits and priorities 9. Call the team back together and get feedback on the mock-ups and override parameters 10. Make final revisions, and include in scope documents provided to the controls contractor We often say in the commissioning industry that we commission systems to operate according to the designer s intent. In many cases we have the opportunity to contribute to a better design. Making building automation systems more usable, adaptable, and maintainable is an opportunity that will have a significant impact on building performance. Len Beyea: Optimizing BAS Information for Operator Effectiveness and Optimal Control 14