📐 Reference Library
Tables, formulas, diagrams, and field workflows — the stuff you look up on the tailgate.
16 guides · page 1 of 2
Voltage Drop: Why It Matters and How to Calculate It
Every conductor has resistance, and every foot of wire costs you a little voltage. Here's the working electrician's guide to voltage drop: the formulas, the NEC recommendations, and the field shortcuts — plus our calculator that does it for you.
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Neutral vs. Ground: The Difference Every Electrician Must Explain Correctly
The neutral and the ground both eventually land on the same bar in the panel, which is exactly why so many people mix them up. Here's the actual functional difference, why the NEC keeps them separate everywhere except the service, and where I've seen guys get burned confusing the two.
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Transformer Basics: Step-Up, Step-Down, and How They Work
Transformers show up everywhere in this trade, from the pole outside a house to the dry-type unit feeding a panel in a commercial mechanical room. This walks through how they actually work, what turns ratio means for your voltage and current, and the practical stuff you need to know before you land conductors on one.
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Short Circuit Current Calculations: An Introduction
Available fault current isn't just a number on a label study - it determines whether your breakers and panels can actually survive a fault without exploding. This is a plain-language introduction to how the point-to-point method works and why AIC ratings matter more than most electricians treat them.
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Insulation Resistance (Megger) Testing Basics
A megohmmeter tells you whether a conductor's insulation is still doing its job before you energize — catching a failing motor, a damaged run, or a wet cable before it faults. Here's what the test is, how to read it, and how to do it safely.
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Lockout/Tagout Basics: Establishing an Electrically Safe Work Condition
Lockout/tagout is how you make sure the circuit you're working on can't be energized by anyone — including yourself. Here's the plain-language walkthrough of the steps and the one that people skip at their peril: verifying dead.
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Arc Flash Safety Basics for Electricians
An arc flash can release enough heat and pressure to cause fatal burns in an instant — and residential and light-commercial workers aren't immune. Here's a plain-language primer on the hazard, the boundaries, and the habits that keep you alive.
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How to Size a Subpanel Feeder (Field Walkthrough)
Sizing the feeder to a subpanel comes down to a load calculation, the right conductor and breaker, a properly sized grounding/bonding scheme, and the neutral rule people forget. Here's the working electrician's walkthrough — verify against the NEC.
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Residential Wire Size Chart (Ampacity Quick Reference)
A field-reference rundown of the common residential conductor sizes, their typical breaker ratings, and the everyday circuits they serve — plus the derating and terminal-rating gotchas that trip people up. Always verify against the NEC and local amendments.
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Motor Circuit Calculations Explained (NEC Article 430)
Motors break the normal rules: you size the wire and the overload protection from a table value, not the nameplate, and the breaker is deliberately oversized to let the motor start. Here's why motor circuits look backwards until you understand what's really going on.
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Residential Load Calculations Explained (NEC Article 220)
A load calculation is how you prove a service or circuit is big enough — without guessing. Here's the standard-method walkthrough: what to add, where the demand factors come in, and why 'add up every nameplate' gives you the wrong (and oversized) answer.
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Ampacity and Derating Explained (NEC 310.16)
A wire's rating on the table is only the starting point. Heat from the surroundings and from bundling with other conductors chips away at it — and if you skip the derating, you can overload a conductor that looks perfectly legal on paper. Here's how it really works.
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