Electrical Failures in Commercial Buildings: A Forensic Investigation Guide

The power goes out mid-shift. A burning smell fills the hallway. By the time investigators arrive, the contractor, the building owner, the tenant, and the insurance adjuster each have a different theory about what happened, and all of them believe the evidence supports their position.

Electrical failures in commercial buildings rarely come with easy answers. Electrical damage may result from an initiating electrical event, exposure to a fire originating elsewhere, progressive deterioration, or a combination of factors. Distinguishing among those possibilities is often central to the technical investigation. 

For claims professionals and attorneys, understanding how forensic investigators work through it is the starting point for a sound technical review. This article explains how failures are categorized, what standards govern the investigation process, what methods determine probable cause, and what a completed investigation produces.

Key takeaways: Understanding electrical failure investigations

Electrical failures in commercial buildings involve complex technical and legal questions. These key points can provide a starting point for insurance claims managers and litigation attorneys.

What matters most

• Electrical failures represent a meaningful share of nonresidential building fires each year, as documented in publicly available fire loss data
• When fire is involved, an important question is whether electrical activity contributed to ignition or whether observed electrical damage resulted from fire exposure
• Fire and explosion related investigations apply the scientific fire investigation methodology described in NFPA 921, along with electrical engineering methods and other standards appropriate to the issues being evaluated

How investigations typically work

• Forensic investigators document the scene, collect physical evidence, and perform laboratory analysis to identify probable causes
• Multiple analytical methods, including arc mapping, microscopic examination, and thermal imaging, are often combined to cross-check findings

Understanding these fundamentals helps stakeholders evaluate the quality of forensic findings. Contact us to discuss how forensic engineering expertise applies to a specific electrical failure claim.

What is an electrical failure?

An electrical failure occurs when an electrical component or system can no longer perform its intended function or operates outside its intended parameters. Investigators distinguish the initiating event or condition, the physical failure mechanism, and the resulting damage because each may represent a different part of the failure sequence. 

That gap between trigger and visible damage is what makes these cases complex: a circuit breaker that trips may indicate the system was protecting itself, but the underlying problem may have been developing for a long time before that trip occurred. A forensic investigation seeks to work backward from the evidence to answer three basic questions: what went wrong, when did it start, and what caused it?

What types of electrical failures occur in commercial buildings?

Commercial electrical failures fall into several distinct categories, and investigators typically examine each one before drawing conclusions about cause of loss.

Overcurrent events

An overcurrent condition occurs when current exceeds the rated or intended current-carrying capacity of a conductor or equipment. It may result from an overload, short circuit, ground fault, or other condition, with the magnitude and duration depending on the particular event and protective devices involved. Gradual overcurrent problems are harder to detect because the damage builds slowly; investigators look for heat discoloration, brittle insulation, and other signs that a circuit ran hotter than it should have long before the incident occurred.

Arc faults

Electrical arcing occurs when current flows through an unintended conductive path or gap, producing localized heating and potentially molten or vaporized conductor material. Depending on the available energy and surrounding materials, arcing may contribute to ignition or may occur as a consequence of an existing fire. After a fire, investigators may evaluate whether observed arcing contributed to ignition or occurred as a consequence of fire damage, while considering the electrical evidence in the context of the overall scene. 

Ground faults

A ground fault occurs when current flows along an unintended conductive path to ground or grounded conductive material. The magnitude, duration, and effects of a ground fault depend on the electrical system, fault path, protective devices, and other conditions present.

Equipment, component, and wiring failures

Not every electrical failure traces to a dramatic event. Many develop slowly as equipment ages, components wear out, or installation problems that went unnoticed at the time finally cause damage, which is why investigators typically examine the entire electrical pathway rather than focusing on a single component. Loose or corroded connections are among the most common sources of electrical fires in commercial buildings, because the resistance at a loose connection point is what generates the heat.

Power quality and transient events

Power quality disturbances, such as voltage sags, swells, transients, interruptions, or harmonic distortion, may originate within or outside a building and can affect the operation or service life of susceptible equipment. When investigators suspect a power quality problem, they look at the damage pattern across multiple pieces of equipment.

Environmental and mechanical damage

Commercial electrical systems run through walls, ceiling spaces, conduits, and mechanical rooms, spaces that expose wiring to moisture, corrosion, vibration, and physical impact that have nothing to do with how much electricity flows through them. This category typically becomes relevant when the damage pattern suggests something developed slowly rather than all at once, and subtle evidence such as corroded connections or insulation deformed by sustained vibration may help explain why a system that appeared functional began to fail.

What standards guide electrical failure investigations?

Four frameworks shape how forensic electrical investigations are conducted and how findings are presented in claims and litigation.

Investigation methodology: NFPA 921

NFPA 921, the Guide for Fire and Explosion Investigations, provides a widely recognized methodology for investigations involving fire or explosion, including evaluation of electrical evidence when electrical activity may be relevant to origin or cause. Its scientific-method framework calls for systematic data collection and analysis, development of hypotheses, and testing of those hypotheses against the available evidence before reaching conclusions. This structured approach matters in litigation because it may help demonstrate how an investigator reached a conclusion and why alternative theories were ruled out.

Code compliance: the NEC

The National Electrical Code (NEC) establishes minimum design, installation, and protection requirements for electrical systems in jurisdictions that have adopted it, though requirements vary by state and locality, and many jurisdictions adopt code editions on different timelines. When a failure occurs, investigators commonly compare the condition of the system against the NEC version that applied when the system was originally built or last modified, examining not just wire sizes but whether equipment was appropriate for its environment and connections were properly made.

Technical standards: IEEE

The Institute of Electrical and Electronics Engineers (IEEE) publishes numerous standards and recommended practices addressing power systems, protection, equipment performance, power quality, and related electrical topics. Depending on the system and failure mechanism, applicable IEEE guidance may assist investigators in evaluating equipment performance and protective-device response.

Professional and ethical standards: NSPE and NAFE

Professional engineering ethics emphasize competence, objectivity, and integrity when engineers perform forensic work or provide technical opinions. Investigators should clearly identify material assumptions and limitations and objectively evaluate evidence relevant to the technical questions presented. A well-documented investigation is what makes compliance with all of these standards demonstrable in the first place.

How is an electrical failure investigated?

A forensic electrical investigation in a commercial building typically moves through six steps. Commercial buildings present more complexity than residential properties: layered systems, decades of modifications, multiple tenants, and integrated safety infrastructure can all make it harder to isolate where a problem started.

Scene documentation

Before anything is moved or removed, investigators typically photograph electrical components, record how circuit breakers and protective devices were positioned on arrival, and document how equipment in the affected area relates to the fire or damage pattern. In commercial buildings, they also locate panel schedules (the directory inside a breaker panel identifying which circuit controls which area) and one-line diagrams (simplified drawings of the overall electrical layout), which may help establish what the system was designed to do and how it was configured at the time of the incident.

Evidence collection

Investigators collect physical items (damaged wiring, melted components, failed insulation) under chain-of-custody procedures. Early involvement matters: if wiring is removed or debris cleared before documentation is complete, it may become difficult or impossible to distinguish damage from the original event from damage caused during cleanup.

Arc mapping

Arc mapping documents the locations and relationships of identified arc sites and may assist in evaluating fire origin and electrical involvement when interpreted with the other available scene evidence. Investigators examine accessible conductors and other electrical components for evidence of arcing and document the locations and relationships of identified arc sites. Those observations are interpreted with circuit information, fire patterns, protective-device operation, scene chronology, and other evidence rather than relying on arc-site appearance alone.

Records and data sources

Records help establish what the system’s condition was before the incident, context that physical evidence alone may not reveal. Commercial buildings often have maintenance logs, prior inspection reports, electrical system drawings, and documentation of equipment changes; investigators may also seek utility records to identify any service disturbances near the time of the event.

Laboratory inspections

When physical evidence requires closer examination than is possible at the scene, investigators inspect items in a laboratory environment. The central question is the same one that runs through the entire investigation: did the electrical system cause the damage, or did damage from another source affect the electrical system? Rimkus materials science capabilities support this work through stereomicroscopy, metallography, scanning electron microscopy with elemental analysis, and non-destructive testing methods. 

Root cause analysis

Root cause analysis evaluates the initiating event, failure mechanisms, contributing conditions, and sequence of events supported by the available evidence. Investigators develop and test plausible hypotheses against the available evidence to evaluate whether the failure involved design, installation, maintenance, operation, environmental conditions, external events, or a combination of contributing factors.

What does a forensic electrical investigation produce?

A completed investigation produces two primary outputs for claims handling and litigation.

Cause-and-origin findings and technical report

The central output is often a cause-and-origin determination: a professional opinion identifying the probable source of the problem, the likely failure type, and the sequence of events that may have led to the incident. When requested, a technical report will document the observations, evidence, methodology, analysis, assumptions, limitations, and conclusions that can be used to inform subsequent claims evaluation, recovery analysis, or legal proceedings.

Expert witness support

When a case proceeds to litigation or dispute resolution, the forensic engineer may provide expert witness testimony, translating the investigation’s technical findings into language accessible to judges, juries, and mediators who may have no electrical background. The credibility of that testimony typically depends on the quality and rigor of the underlying investigation, which is why the two are generally understood to be closely connected.

Supporting electrical failure claims with forensic investigation

For claims professionals and attorneys managing electrical failure matters, a well-documented technical investigation can inform decisions involving damage evaluation, potential recovery, repair planning, and subsequent legal or expert review. Commercial electrical systems present interconnected failure modes, competing explanations, and evidence that can be compromised within hours of an incident. A structured investigation, one that follows recognized methodology from scene documentation through root cause analysis, provides the analytical foundation those decisions require.

Our forensic electrical engineers support complex commercial claims with 40+ years of experience across investigation, laboratory analysis, and expert testimony. Contact Rimkus to discuss how that support applies to a specific matter.

Frequently asked questions

What records and data should be preserved immediately after a commercial electrical failure?

The most important early step is to avoid disturbing the scene before a forensic investigation has taken place. Priority records include maintenance logs, prior inspection or infrared survey reports, panel schedules, and any fault or alarm data from building management systems.

How do aging systems and building modifications increase the risk of electrical failures?

Aging electrical infrastructure may develop insulation deterioration, corrosion, connection degradation, or component wear depending on materials, environment, loading, maintenance, and service conditions. Building modifications can also change electrical loading or system configuration, which investigators may evaluate when determining whether those changes contributed to a failure.

How can investigators tell whether arcing caused a fire or resulted from one?

Investigators evaluate the locations and characteristics of arc sites together with circuit configuration, fire patterns, electrical-system status, protective-device operation, scene chronology, and other available evidence. Laboratory examination may help determine whether conductor damage is consistent with electrical arcing or other thermal effects, but arc-site morphology alone generally cannot establish whether the arcing initiated the fire or occurred as a consequence of fire exposure.