By Steve Rizer
When deciding which facilities to include in a large-campus/multi-building retro-commissioning project, it is important to identify heating, ventilation, and air-conditioning (HVAC) systems that are scheduled for replacement within the next five years, Christian Marsh-Frydenlund, a project manager for Eaton Corp.’s Energy Solutions Group, told a group of construction professionals attending a recent WPL Publishing webinar. “[Such systems] are not ideal candidates for retro-commissioning because retro-commissioning is focused on persistence of energy savings, so if you’re implementing an energy strategy for equipment that will be replaced, you’re going to minimize the long-term value of the retro-commissioning project.”
Here is some other advice she offered to identify facilities for such projects:
- In determining which facilities to include in a campus retro-commissioning project, it is important to group facilities that have HVAC systems similar in age. “This can definitely help the overall retro-commissioning process efficiency for testing, monitoring, and implementation. Facilities with newer systems are still great candidates to be included in a campus retro-commissioning project. Experience indicates that many of the newer systems are the ones with the most comfort-enhancement and energy-savings potential. Buildings with older systems are not always ideal candidates because the controls are often very simple or the repairs cannot be achieved without total control system replacement due to the age of the components.”
- Another key factor involves the HVAC control system. “The HVAC control system plays a crucial role in identifying facilities for large campus retro-commissioning projects. The control system is the vehicle that the retro-commissioning team uses to collect information, test systems, pull trends, and implement enhanced control strategies. It can also be used to measure and verify savings. So, in determining which facilities to include in a campus project, several lessons pertaining to the control systems can be applied. It’s critical to identify differences, limitations, and capabilities of these systems before the project starts. Doing so will maximize the value of the entire process. In this step, it’s encouraged to categorize buildings by pneumatic or electronic control because testing, trending, and enhanced control opportunities are different for pneumatic and electronic systems. Additional trouble-shooting may be required for pneumatic systems in determining why control components are not responding during the [retro-commissioning] testing process, for example, and grouping buildings that have these systems can allow for more efficient testing to occur. Control systems can also be very limited by their data-trending capability. Identifying systems with limited capabilities is critical, especially if many of the observations and verification of the project are intended to come through trend data. If the system cannot perform as functioned, an upgrade should be performed or alternate methods of metering verification performed. A question that comes up very regularly is ‘How can trend data be collected if the BAS or automation system cannot provide this feature?’ The most common response that we provide to this question is to provide trending capabilities with portable data-logging equipment. Sometimes the automation system will have trending capabilities, but it’s not capable of archiving trends. So in this situation, the project could cover the cost of installing archiving capability. So, identifying these systems where existing trends are available will improve the retro-commissioning process for a campus project. Facilities should also be grouped together where testing of the HVAC systems through the control system can be accomplished easily or where the testing will require additional controls hardware or where control is local to the HVAC system and cannot easily be performed through the system. Categorizing facilities in this way assists in narrowing down the list of buildings to include in the project. If the systems cannot be easily tested, they should not be included in the project. Facilities can also be selected for inclusion based on the control schematics and sequences of operation. For example, assuming multiple facilities have packaged rooftop units, which are operated using the same sequence of control, these facilities could be selected for a large-campus or multi-site project since the testing, monitoring, and controls optimization recommendations derived from the process will be similar.”
- “In selecting facilities for the large project, understanding the pros and cons of newly constructed facilities can enhance the benefits of paying through the process. New facility-commissioning results can assist in the selection of facilities. The commissioning report itself can provide valuable information in sequences of control, issues identified through the commissioning process, and all of this can be used as a valuable clue in selecting facilities to include in a retro project where sequences of control and comfort can easily be applied. Understanding the warranty-phase terms for a new facility is also critical. In some instances, adjustments made as part of a retro-commissioning project could have the potential to void a warranty. Knowing this would prevent some new facilities from inclusion in a larger retro-commissioning project.”
- As facilities age, they can require renovations that impact the retro-commissioning project, so it is important to exclude any facilities that are currently undergoing major renovation or are planned for a major renovation, and those that could be demolished or sold in the near future. “Retro-commissioning projects … focus on persistence of energy savings, so implementing energy strategies in new facilities where the HVAC systems could be removed or reconfigured and where a whole facility could be eliminated from the candidate pool will minimize the long-term impact of the retro-commissioning project.”
- “Ideal candidate facilities for these types of projects have building information such as drawings, control schematics, sequences of control, and recent TAB reports readily available and in accessible form. The facility information provides the history of the retro-commissioning project or the history for the retro-commissioning project because the team will need to review and evaluate opportunities for enhanced control and comfort improvements. Acceptable information can be in many different forms, perhaps even electronic files, facility operator manuals, hard copies of original building drawings, and various other forms, but those are the most common ones that we see. Without accurate and accessible information, testing of HVAC systems and energy-savings calculations can be impeded. Facilities without accurate and accessible information are not ideal candidates for these types of projects.
- “Candidate facilities will have building-level utility meters at a minimum. Buildings with HVAC system sub-metering capabilities are ideal for these types of projects. System sub-metering data can be used to benchmark the system energy usage. Once modifications are made to control strategies, the data can be reviewed to verify the level of savings obtained. This makes measurement and verification much simpler. The catch here is that these systems are very hard to find.”
- “So what do we do if we don’t have sub-metering or building-level utility meters? The project does not have to be abandoned if building-level data is not available. Campus data can be used to benchmark utility usage. This adds a level of complexity to the savings-calculation methodology and verification, but the utility data is used to calibrate savings and verification data, and so the retro-commissioning project team needs to have a very clear understanding that the level of accuracy of the savings and the verification data is only accurate to the campus level.”
- Another consideration relates to operation and maintenance. “Generally, the selected facilities need to meet the objectives of the project. Understanding the limitations and capabilities of the O&M [operations-and-maintenance] process on the campus can assist in identifying a target group of buildings for this type of a project. If the objective is to implement enhanced control strategies, ideal facilities would be those where routine O&M is performed. So, routine maintenance makes new control strategies much easier to implement. If the objective is to implement repairs, ideal facilities would be those that have received minimal maintenance. This approach is generally less valuable since many of the repairs could be capital-intensive. Whole HVAC systems may need to be replaced, and again, retro-commissioning focuses on making low-cost improvements to the control of HVAC systems, so those approaches are not ideal.”
During the webinar, Marsh-Frydenlund also discussed the differences between an energy audit and retro-commissioning.
Unlike an energy audit, retro-commissioning is not focused on identifying capital-intensive projects such as equipment replacement, Marsh-Frydenlund explained. “Analysis of water systems is often not included, and lighting systems are excluded as well. The goal for retro-commissioning is focused on optimizing building performance through low-cost projects, and that’s a key difference between a retro-commissioning project and an energy audit.
“Improvements can be made during the process, and energy audits are generally delivered in a report, and then funding for recommended projects can be obtained at a later date. This is a major difference between these two types of projects. The retro-commissioning scope includes implementation of repairs and optimized projects through the process, adjustments can be made right away without seeking additional funding, so savings and comfort improvements can be realized very quickly.”
In addition, Marsh-Frydenlund and colleague Megan Van Wieren addressed the following questions during the webinar:
- How can trend data be collected if the building automation system is not capable of providing this feature?
- Can energy usage still be benchmarked if a campus does not have sub-metering at the facility level?
- Should implementation of repairs and controls modifications be included in the project scope?
- How are the results from monitoring and testing documented?
- Should verification of repairs be included in the scope?
To obtain a recording of the webinar, entitled “Maximized Value: Lessons Learned from the Trenches of Large-Campus/Multi-Building Retro-Commissioning,” visit
http://constructionpronet.com/Products/retrocomissioning2012.aspx.
