Assessing replacement of electrical systems
Replacement of electrical systems is a study of economics and risk. Factors including age, safety, reliability, efficiency, and energy costs must be weighed in conjunction with replacement costs and liability risk to formulate and prioritize upgrade plans. A comprehensive cost-benefit analysis study for each electrical subsystem will allow facilities to plan short-term and long-term expenditures for maintenance and upgrade programs for prudent facility reinvestments, replacements, and growth.
- Illustrate the reasons that electrical engineers should conduct studies of electrical and power systems
- Summarize the types of electrical equipment that should be reviewed for replacement
- Analyze the codes and standards that dictate equipment design.
Facilities' needs and their aging electrical systems change over time. Aging systems and newer technologies constantly challenge facilities managers in repair and replacement considerations. Systems retro-commissioning, assessments, and master planning analyses are all methods to understand whether electrical systems are safe and operating correctly and efficiently to meet performance goals.
Such studies can indicate if systems can put the facility at risk, how systems are currently performing, can provide measurements, and set priorities for improvements. Balance scope, schedule, and cost of these improvements so business budgets, operations, and schedules can then be prudently planned.
Why and when to analyze
The performance of systems, operation, and users tend to drive the economy of the business world. Goals drive performance metrics that, in turn, will drive programs and action as well as associated operating costs. Performance measures must be communicated to deliver expected results and drive the systems analyses. Typical goals of an electrical system analysis may include age and condition, safety and security, code compliance, capacity for growth, reliability and redundancy, energy efficiency, physical distribution, ease of operation, and maintainability.
Facilities and their systems should be evaluated every 10 years to realign with current business strategies. Planning may include spaces to be repurposed, technology changes, and systems that operate less efficiently as they age. As most electrical distribution equipment have a 20-year expected life, 10-year status investigation increments are adequate to cover new, mid-life, and end-of-life evaluation.
It also becomes time to analyze electrical systems when facility growth or renovation is anticipated, associated affecting systems are due for replacement, failures begin to regularly occur, operating or energy costs unexpectedly rise, or when third-party funding opportunities (e.g., energy grants, utility incentives) become available for a known upgrade or need.
What to analyze
Professional design, service, and contracting organizations offer varying methods and analysis tools. Firms with the wide or narrow focus of systems expertise specific to the needs of the facility assessment should be chosen. For instance, infrared electrical inspections quickly find hot spots caused by defects in connections and components. Specific overall assessment personnel should have a minimum of 15 to 20 years of expertise and are knowledgeable in long-term building systems care and applicable codes and standards. They must be knowledgeable in the nuances of older and newer technologies, retrofits, and lifecycle costs and be sensitive to the overall goals of the facility such that they can help to prioritize any needs of these systems. The facility's own staff will tend to focus on what they are used to or what is in need of repair; therefore, they may lack the flexibility for change or global insight necessary in both short- and long-term cost-benefit solutions.
Many factors come into play when analyzing and prioritizing electrical equipment needs. Life safety hazards should be prioritized first to maximize human safety and minimize potential high legal and operational risks.
Electrical equipment deterioration may be due to daily temperature cycles, collection of dust, condensation, mechanical wear of circuit breaker contacts and contactors, weakening of operating springs, deterioration of insulating materials, and rusting enclosures. The industry life expectancy for commercial-grade electrical systems in buildings is generally 20 to 30 years, if maintained properly, outlined as follows:
Electrical equipment ages at different rates based upon the quality of equipment, maintenance, and environment. Enhanced preventive maintenance care, regular duty-cycle operation, and lower operating temperatures will extend the equipment's useful life. Aging electrical components are potential hazards, as their failure is unpredictable and can cause arcing, fires, failures, and associated human-safety issues.
Low-voltage cabling materials that should be considered for replacement include pre-1960s conductors having asbestos insulation and pre-2000 aluminum compression lugs, which may be subject to arcing conditions. Aging equipment will eventually reach a condition in which its reliability becomes questionable.
Code and safety issues
Fault-current rating: Electrical equipment fault-current ratings are based on the highest electrical current the equipment can withstand in the event of a short-circuit condition. Calculating the fault-current rating entails identifying the available fault current, which originates from the utility, generators, and running motors. If the available fault current exceeds the equipment's rating and a fault occurs in the system, then a catastrophic failure of the equipment could occur. A system can become unsafe due to remodeling and expansion projects that add additional fault current without updating or maintaining an accurate fault current study.
Selective coordination: Electrical system coordination is required by NFPA 70: National Electrical Code, Articles 517, 700, and 701, and NFPA 99: Health Care Facilities Code. It assures that each overcurrent device trips in sequential order, isolates the problem condition, and does not cause unnecessary disruption of power upstream. Many times, interpretation prudently enforces the same coordination on normal power systems and is considered good practice.
Ground-fault protection is handled similarly in larger health care facilities. These facilities require two levels of protection, the main service overcurrent protective device (OCPD) and the second level OCPD to assure a feeder breaker opens on a fault condition prior to tripping the main circuit breaker. Large health care emergency systems also are required to have ground-fault alarm indication, not tripping, as the system is a facility's last opportunity to maintain power in an emergency.
Arc flash hazard: Arc flash ratings are based on the equipment's ability under a fault condition to cause an explosion, or arc fault. The rating defines the equipment's ability to deliver energy and correlates to the personal protective equipment (PPE) gear an electrician is required to wear to be safe when working on or around energized equipment. Safety parameters are defined in NFPA 70E: Standard for Electrical Safety in the Workplace.
The incident energy level is directly proportional to the available fault current level available at the equipment and the time it takes to clear a fault condition. Older equipment may take more time to clear, which makes for increased concern.
Although the arc-flash-hazard level of electrical equipment is not a specific code requirement, except to OSHA, it is often a determining factor in the decision to replace existing equipment. The electrical system of many occupancies must remain energized during maintenance procedures, and the lower the arc flash hazard of the equipment, the safer the personnel who are working on that equipment.
Seismic provisions: Essential electrical equipment bracing is now required in seismic zones for essential buildings, such as health care facilities. Essential buildings, themselves, are also now similarly required to be structurally seismically braced.
Lightning protection: A lightning-protection risk analyses should be performed per NFPA 780: Standard for the Installation of Lightning Protection Systems to evaluate the need for building protection. Older systems should be reviewed for condition and connectivity conformance with this standard. Protection of buildings' electronic equipment and associated insurance carrier requirements and rates also should be integral to the evaluation.
Grounding and bonding: Bonding of metallic components and earth grounding for electrical systems is commonly misunderstood, and human safety and equipment protection may be compromised if not properly accomplished. Independent-source grounding methods at services, transformers and generator systems, exposed equipment grounding, corrosion of grounding electrodes, and patient-care grounding systems should be properly evaluated.
Harmonics ratings: Overheating of electrical equipment may be caused by nonlinear electronic sources. Proper harmonic equipment ratings or harmonic-mitigation techniques should be reviewed.
Testing reports: Equipment testing reports per the InterNational Electrical Testing Association's acceptance testing specifications are valuable for outlining equipment conditions, duty cycles, and loading. Frequency and time-of-day parameters of the testing provide additional insights on the validity of the data.