Why is this site called First Fault? Two technical meanings of one word
Why "first fault"?
Because "fault" is a term of art in more than one field, and the collision is a good illustration of why vocabulary deserves its own site. In law and insurance, fault means legal responsibility. In electrical engineering, a fault is an unintended current path — current going somewhere the design did not intend — and a first fault is the initial one to occur in a system that may tolerate it before a second fault makes conditions dangerous. Neither meaning informs the other.
The electrical sense, briefly
Electrical faults are classified by where the current goes and how it behaves. A federal consumer-safety primer on arc fault circuit interrupters distinguishes an arc fault — current arcing across a gap, as through damaged insulation — from a ground fault, current taking an unintended path to ground, and explains that the two are addressed by different protective devices, AFCIs and GFCIs (CPSC Publication 5133). The distinction is why a home may have both kinds of device, and why one is not a substitute for the other.
The phrase "first fault" comes from how a system's earthing arrangement is designed. The international low-voltage installation standard for protection against electric shock defines the TN, TT and IT earthing arrangements and the conditions that follow a first fault in each (IEC 60364-4-41). In some arrangements a single fault does not by itself create an immediately hazardous condition, which is what makes insulation monitoring and the sequencing of faults a design topic rather than a trivia question.
On the US installation side, the canonical reference for grounding, bonding and overcurrent protection requirements is the National Electrical Code, published and revised on a regular cycle (NFPA 70). Like insurance statutes, it has revision cycles and adoption dates — which is the whole reason this site refuses to restate code numbers or statutory figures from memory. Standards and statutes both have a version, and a claim without one is incomplete.
The legal and insurance sense
In a liability context, fault refers to legal responsibility for harm, established under rules of negligence and apportionment that vary by state. "No-fault" insurance does not mean no one was responsible; it describes a system in which certain injury payments come from the injured person's own policy without waiting on that determination. That is the subject of the rest of this site — start with is Florida a no-fault state or the glossary.
Family law supplies a third use: "no-fault" grounds for divorce, meaning grounds that do not require proving misconduct. See why "no-fault" comes up in divorce.
Why the distinction is worth five minutes
Searches for "fault" pull all of these together, and so do automated summaries. If you came looking for insurance and landed on arc-fault devices, or the reverse, the words were doing the confusing — not you.
One boundary, stated plainly: nothing on this page tells you how to inspect, test, install, or work on any electrical system. Those are matters for a licensed electrician and for the qualified-person and safe-work-practice requirements in the workplace electrical safety standard (NFPA 70E). This is a terminology page and nothing more.