Commissioning electrical and power systems
Essential/standby power equipment and system components are some of the most critical electrical systems to be commissioned in nonresidential buildings.
Know the codes and standards that govern commissioning of emergency power supply systems.
Understand the emergency power system classifications.
Know the documentation required throughout the commissioning process.
Commissioning is the bridge from the design phase through construction and into occupancy. Its purpose is to ensure that building mechanical and electrical systems operate as intended per the owner’s project requirements (OPR). As defined by ASHRAE Guideline 0-2013, the commissioning process is the owner’s “quality-oriented process for achieving, verifying, and documenting that the performance of buildings, systems, and assemblies meets defined objectives and criteria.” In electrical commissioning, the goal is primarily to confirm reliability. This is in contrast to LEED commissioning as defined by the U.S. Green Building Council (USGBC), which has been driven by, and has focused on, energy conservation.
One of the most critical electrical systems to be commissioned in nonresidential buildings is essential/standby power equipment and system components. Given their importance, the NFPA provides specific requirements in NFPA 70: National Electrical Code (NEC), 2013; NFPA 99: Health Care Facilities Code, 2013; and NFPA 110: Standard for Emergency and Standby Power Systems, 2013. (These editions of the associated codes and standards are referenced throughout this article unless otherwise noted).
With these requirements in mind, a standard commissioning process can be developed as outlined by ASHRAE Guideline 0-2013. This allows an owner to define activities and deliverables, such as design reviews, submittal reviews, prefunctional checklists, and functional performance test documents. These tools, along with site observations and owner training, give the owner a level of confidence that all components of the emergency power supply system (EPSS) operate as intended. NFPA 110 provides the defining requirements for these systems and holds the design engineer, installing contractor, and owner accountable for achieving a higher standard of product. At the end of construction, the enforcing agency, the authority having jurisdiction (AHJ), becomes the judge for verifying that the system is acceptable. From a commissioning perspective, the goal for an EPSS—and any electrical and power system—is to ensure that the owner receives an electrical system that meets the OPR for NFPA and passes acceptance by the AHJ.
What the code requires
One of the biggest coordination issues—comprehension of the code and the application for the EPSS—usually occurs in the design phase of a project. Despite the best intentions, field acceptance testing usually does not go as planned the first time. The EPSS, like many systems, evolves through programming and design via value engineering and cost estimating. The NEC outlines “the provisions [that] apply to the electrical safety of the installation, operation, and maintenance of emergency systems…to supply, distribute, and control electricity for illumination, power, or both, to required facilities when the normal electrical supply or system is interrupted.”
NFPA 99, NFPA 101, and NFPA 110 then form the baseline of the minimum requirements. The commissioning design review is a good time to look for references in the project specifications to these code standards and additional testing that would be recommended to meet the OPR. One classic example is properly defining the class, level, and type of the EPSS (see Figure 1). These tags are not always clearly defined in the project specifications (see Figure 2). There might be a reference in Part 1 (references and codes) and perhaps Part 2 (product data), but typically it is not as clear as: “The generator and EPS components shall be Class 2 (hr), Type 10 (sec), Level 2 (less critical to human safety).”
It would be great if the EPSS was defined that way, but through design reviews, a commissioning agent can ask those questions to get that level of detail. Those three tags help explain how a system is intended to be used (see “EPSS classifications”).
With this information, questions regarding fuel tank sizing, alarms, site placement, and routine maintenance can be discussed with the design team through the design reviews to ensure that the OPR is satisfied.
Much of the value of the commissioning process in the design phase is to ensure that the EPSS is properly specified for purchasing by the contractor. Sometimes components that are required to meet the standard Part 3 of the project specification (execution, installation, and testing) are not properly identified in Part 2. For example, many standard specifications require backpressure testing. This is a very valuable test for systems that have an EPSS located in a building that has a lengthy exhaust stack. A common problem is that this test is also specified for exterior installed generators that have a factory installed muffler and exhaust system. The engineer must evaluate the return on investment in requiring this test. Additionally, a testing port in the exhaust discharge close to the manifold must be installed at the factory to allow for the insertion of a water manometer, or gauge to measure inches of water (see Figure 3). Most generators do not include this test port unless it is requested.
Further, many design specifications use standard, but vague, testing language in Part 3 of technical specification sections such as, “Load test shall comply with requirements of NFPA 110.” While this reference is factually accurate, it does not clearly define coordination or specific requirements. This ambiguity places the burden on the installing contractor, who almost always puts the onus on the manufacturer of the emergency generator. NFPA 110, Chapter 7 addresses acceptance testing and load bank requirements for EPS systems. The commissioning agent will seek to eliminate such gaps of coordination in the project specification so that the roles and responsibilities are clearly defined and understood, specifically between trades and other vendors. This provides for more accurate costs, fewer rejected/commented submittals, and something to reference during the testing phase for conflict resolution.
More specifically, NFPA 110, Chapter 7.13 can be interpreted many different ways with respect to load bank testing hours, connection of the load banks, and who must be present. The code does not explicitly require the AHJ to be present at this time of testing, but according to NFPA 110, chapter 7.13.3, “The authority having jurisdiction shall be given advance notification of the time at which the acceptance test is to be performed so that the authority can witness the test.” This is part of the coordination effort that commissioning agents should not lead, but at a minimum should alert the contractor to perform.
Up through NFPA 110 (2005 and older), Chapter 22.214.171.124, line 11, requires that the first load bank test “shall be continued for the minimum time required by Table 4.1(a) for the class, or 2 hr maximum." Additionally, 7.13.6 requires that “A load shall be applied for a 2-hr, full load test. The building load shall be permitted to serve as part or all of the load, supplemented by a load bank of sufficient size to provide a load equal to 100% of the nameplate kW rating of the EPS, less applicable derating factors for site conditions.” In NFPA 110 (2010 and later), these requirements were adjusted to remove some of the confusing and often misunderstood timeframes. Now, 126.96.36.199.3.10 requires a minimum of 1.5 hr, regardless of the class, and the additional 2 hr of load bank testing, per 188.8.131.52.
Another often misunderstood reference in the code related to load bank testing is where the load bank connection can occur. This requires referencing the definition of an EPSS. The EPSS is the emergency power supply system that NFPA 110, Chapter 3.3.4 states is “a complete functioning EPS system coupled to a system of conductors, disconnecting means, and overcurrent protective devices; transfer switches; and all control, supervisory, and support devices up to and including the load terminals of the transfer equipment needed for the system to operate as a safe and reliable source of electric power.” If the project in question would have a standby diesel generator, then the EPS would be that generator and the EPSS would include the generator, the automatic transfer switches (ATSs), and all associated conductors in between, including breakers and switchboards. Chapter 7.13.1 (all years) states that after “installation of the EPSS, the EPS shall be tested to ensure conformity to the requirements of the standard with respect to both power output and function.”
It is crucial to understand that the second 2-hr load bank test actually allows for the building load, if any is available, to be included in this testing. That can only occur if the generator is connected to the load bank directly via a spare circuit breaker mounted at the generator or, as is more commonly done, at a switchboard between the generator and ATS. Each installation must be evaluated during design to determine the best location. The generator should be located relatively close to the emergency-related equipment. If a permanent load bank is not in the project design, understanding how the vendor or contractor will route load bank conductors and load bank placement must be addressed. In NFPA 110,Chapter 8.4, supplemental load is not required to be used as part of the routine maintenance, but according to NFPA 110-8.4.2-1, “load that maintains the minimum exhaust gas temperatures as recommended by the manufacturer must meet 30% of the nameplate kW. If the engine cannot be loaded as required, the engine shall be operated until the water temperature and the oil pressure have stabilized…”
Navigating these requirements has become an art form for commissioning agents who wish to educate owners on the value of their services. Often the commissioning agent will include many, if not all, of the NFPA requirements directly in its functional performance test, written in a manner that is easier to follow. Having this functional test written and included as part of the bid package reduces confusion and helps equipment vendors understand the exact acceptance criteria required.
Beyond what the code requires
Many design firms will require ANSI/NETA Standard for Acceptance Testing Specifications for Electrical Power Equipment and Systems requirements for field-related testing that the installing contractor will need to provide. While NETA is not a code, it is considered the bible for field acceptance testing. However, it is not the only testing activity that should be performed by a contractor and witnessed by the commissioning agent (see Figure 4).
Integrating the EPSS testing at the proper time in construction is also a major challenge for the commissioning agent. Space completion, proper ventilation, and fuel delivery are items that the commissioning agent must track beyond the actual installation of the EPSS per the requirements of the project. Tracking these items and understanding their completion is most commonly done as part of the prefunctional checklist. This tool allows the installing contractors to identify when a milestone of installation is completed and ready for review by the commissioning agent. Using this tool to capture many of the project-specific design requirements as well as code requirements helps to ensure a successfully tested EPSS. It also clarifies how other aspects of the project installation are coming along that will allow for NETA testing and start-up to occur.
Understanding the NETA test steps is just as important as understanding the code requirements. NETA requires load bank testing as well as other insulation resistance testing, battery testing, and alarm verification that duplicates what could be provided by others. This duplicative effort can add unnecessary delays and costs to a project. The commissioning agent should discuss these additional tests with the design team for evaluation while the project is still in the design phase.
Beyond physical testing to verify the equipment is built satisfactorily, an operational test that confirms how all of the individual components work together is one of the most important functional tests that can be performed. Pulling all the pieces together as one system and watching them operate in a real-world, controlled condition offers the owner peace of mind. This is particularly valuable with multiple EPS units that will need to operate as one system. Being able to verify that they start, synchronize, and share the building load after the transfer switches operate supports the requirements of NFPA 110 Chapter 6.2. Add in external monitoring by a building automation system or fire alarm and you have what is commonly referred to as an integrated systems test, where multiple systems of the project are tested and verified at one time. Building up to these tests will require heavy coordination, scheduling, and testing by the contractors, vendors, and commissioning agent. Defining and quantifying the number of tests needed to be performed is a costly inventory that must be done during the design phase. Defining the expectations of the project team as early as possible will ultimately save the project time and money.
The commissioning process should be able to support some of these coordination items related to ensuring that the OPR and goals are achieved. Understanding the requirements of NETA, the NEC, and NFPA is crucial for an electrical commissioning agent. These documents not only define the project obligations but also can support the framework for the design through testing phases of the project.
Derek DeJesus is the national commissioning manager and electrical commissioning leader for KJWW Engineering Consultants. He supports the company’s commissioning business development, project oversight, and commissioning program.
Do you have experience and expertise with the topics mentioned in this content? You should consider contributing to our CFE Media editorial team and getting the recognition you and your company deserve. Click here to start this process.