Why Thermal Transient Analysis in Electrical Enclosures Matters for Post-Fire Inspections

The aftermath of an extensive electrical fire is always messy. Plenty of visual damage cues are present, such as melted wires, scorched enclosures, or the lingering smell of burned insulation that is impossible to wash from clothing. Inside these signs are hidden clues that our expert forensic engineers look for, like temperature patterns, thermal gradients, and heat propagation paths.

Our goal is to determine the accurate sequence of events using evidence-based procedures and experienced insights. That is where thermal transient analysis is crucial to our work. We can model how heat moved through an electrical enclosure over time, determining not only what failed, but also the how, why, and when that insurance companies and legal experts require to assign responsibility.

The Limits of Visual Inspection in Post-Fire Investigations

Most post-fire investigations rely too heavily on burn patterns, physical deformation, arc mapping, or the signs of mechanical failures. While those insights do provide some information, they often lack an understanding of how external fire damage can obscure internal fault origins, or that the marks left by arc marks can be too quickly confused with secondary ignition points.

We look past sequential component failures that often appear simultaneous after thermal collapse. Our goal is to reduce the ambiguity of what happened by following strict guidelines, such as NFPA 921 (Guide for Fire and Explosion Investigations), where scientific modeling becomes increasingly essential as physical evidence degrades. That is where we rely heavily on thermal transient analysis.

What Is Thermal Transient Analysis?

The basic idea of thermal transient analysis is to recreate what happened by simulating heat transfers over time within an enclosure, such as a circuit board or equipment housing. That will help determine data points like:

• Heat source intensity
• Heat source duration
• Thermal conductivity (including material analysis)
• Too little or too much airflow (inside the housing)
• Surface emissivity
• Ambient condition impact
• Component spacing, geometry, and protective shielding

Our experienced and licensed forensic engineers can effectively reconstruct the thermal environment over a specific period. We can then generate a timeline of degradation, answering questions such as when the breaker failed, whether the thermal fuse was damaged, or whether the cooling mechanisms were triggered.

Why Thermal Transients Matter in Electrical Enclosures

The trouble with most commercial and industrial electrical system designs is that breaker panels, control cabinets, and junction boxes can all quickly become pressure compartments during a fire. The more temperatures spike, the greater the chance of melting conductors, insulation carbonizing, or vaporizing metals that rupture the rest of the enclosure (and eject burning material outward).

Without the thermal transient analysis to determine the cause of these ejections, it can be challenging to decide whether the fire started inside or outside the enclosure, or if the enclosure was breached by external fire and failed secondary to another factor.

Numerous test studies by teams like the NIST (National Institute of Standards and Technology) have investigated industrial switchgear fires to determine whether thermal propagation occurs inside enclosures or leads to secondary arcs at conductor terminals. That way, engineers like our team have more evidence to distinguish between false positives and trace the actual source of damage during a visual inspection.

Common Inputs for Accurate Thermal Simulations

The most effective way to conduct thermal transient analysis is to gather as much reliable data and information as possible. That may include looking closer at:

• The material components and properties of conductors, busbars, plastic housings, etc.
• Considering the enclosure geometry, especially in relation to vent configurations
• Collecting time-temperature data using infrared cameras and temperature recorders/loggers
• Estimating ignition points using X-ray scans or arc mapping
• Looking closer at ambient conditions at the estimated time of the incident, like temperature, humidity, and airflow

In some unique cases, our expert team at Dreiym Engineering will approach post-fire thermal modeling based on thermal imaging performed during live systems testing. That provides a baseline that we can use to compare post-fire data. We utilize a combination of modern tools and procedures, ranging from field data collection to simulation software and lab analysis.

In most cases, we can generate comprehensive reports that include electrical schematics, system logs, infrared and x-ray imaging, 3D modeling, and more. Not only do these deliverables help prevent future issues in the same or similar systems, but they also help insurance companies figure out how to proactively prevent such risks for other clients.

How Modeling Tools Are Applied in Thermal Transient Analysis

We typically begin with an on-site visual inspection and then collect data through several tools. Our goal is to reverse engineer the enclosure’s geometry, taking into consideration wall thickness, vent placement, and any other internal layouts. We may use CAD-derived mesh modeling or apply material-specific thermal parameters (conductivity, specific heat, emissivity, etc.).

From there, we aim to determine a time-based thermal input using a simulation that calculates the temperature distribution across the entire volume of the enclosure. That could better identify the initiation of an arc or the arrival of fire. We are trying to calibrate information using thermal camera data (if available) or other devices to set reference points. That could also include melting patterns, solder displacement, and discoloration of insulation.

These are only a few examples of how we apply modeling tools to thermal transient analysis. For decades, we have conducted post-fire analysis for clients throughout Texas, Louisiana, Oklahoma, New Mexico, and Colorado. Our fire investigators are also National Association of Fire Investigators (NAFI), Certified Fire and Explosion Investigators (CFEI), and Certified Vehicle Fire Investigators (CVFI). This means we take our time to ensure the information is as evidence-backed and comprehensive as possible for all stakeholders.

Why Thermal Transient Modeling Matters More Than Ever

The modern design of electrical enclosures is only getting more and more complex. Commercial and industrial applications make uncovering failure events that are often not so easy to interpret. It’s common to find systems with programmable logic controllers (PLCs), variable frequency drives (VFDs), and smart connected monitoring for real-time remote notifications. This results in nonlinear load behavior and mixed heat profiles, making the forensic investigation even more crucial in determining responsibility.

We view every thermal model through the lens of technical background and legal or insurance context. Our forensic engineers have frequently been called upon to provide expert testimony in legal proceedings, so we must frame the technical data in a manner that makes it more accessible to non-forensic engineers. That ability to communicate failure points for electrical enclosures goes a long way in helping our clients understand recent events, audit current systems, and prepare for future risk.

Engineering Insight That Moves Beyond the Ashes

The total cost of a commercial fire in the U.S. (combination of damage caused and money spent on prevention, protection, and mitigation) is a total of $329 billion. That was in 2011 and measures about 2.1% of the total U.S. gross domestic product.

Having an experienced and licensed forensic engineering team conduct thermal transient analysis helps identify the story of failure and provide accountability for uncovering or reducing expenses. Our team at Dreiym Engineering is here to ensure you receive all the necessary information about what was responsible, what failed first, and how to prevent it from happening again.

Give us a call today to schedule a consultation, and let’s ensure your systems are better protected for the future.