Read and apply the National Electrical Code: navigation, definitions, adoption, conductor sizing, voltage drop, load calculations, box fill, grounding, GFCI/AFCI, motors and exam prep.

Electrical Code & Installations

## Why it matters

Grounding and bonding are the parts of an electrical system that only matter when something goes wrong, which is exactly why they are easy to get wrong. A missing bond can leave a metal water pipe or appliance case energised. A wrong neutral-to-ground connection can put current on the metal parts people touch. Article 250 is one of the longest and most tested articles in the NEC, and the concepts behind it make the rest of the article readable.

> **Awareness level only.** Grounding and bonding work is done on real systems only under a licensed electrician's supervision with employer training. Never open a panel or touch service equipment to "look" at the bonding.

## Two different jobs

The words sound alike but describe different jobs.

**Grounding** means connecting to the earth. Article 250 says this is done to limit voltages caused by **lightning, line surges or unintentional contact with higher-voltage lines**, and to stabilise the system voltage to earth during normal operation. A grounding electrode system (ground rods, a concrete-encased electrode, a metal water pipe, and so on) connects the system to the earth through the **grounding electrode conductor**.

**Bonding** means connecting metal parts together so they form a **low-impedance path** back to the source. Its job is to carry **fault current** large enough, and quickly enough, to trip the breaker or blow the fuse, and to keep all the metal a person might touch at the same voltage.

The key point: **the earth is a poor conductor**, and it is **not** what clears a fault. If a hot conductor touches a metal box and the only path is through a ground rod and the earth, the current may be far too small to trip a 20 A breaker, and the box stays energised. It is the **effective ground-fault current path** (equipment grounding conductors, metal raceways, bonding jumpers, back to the neutral at the service) that clears faults.

## How the pieces fit together at a service

At a typical dwelling service:

1. The utility delivers a **grounded conductor** (neutral) with the ungrounded (hot) conductors.
2. In the service equipment, the **main bonding jumper** connects the neutral bar to the equipment grounding bar and the enclosure. This is the one point where neutral and ground are joined.
3. The **grounding electrode conductor** runs from that point to the grounding electrode system.
4. From there on, the **equipment grounding conductors** (EGCs) run with every circuit to bond boxes, appliance frames and receptacle ground pins.
5. Downstream of the service, for example at a subpanel, **neutrals and grounds are kept separate**. Joining them again would put normal neutral current on the EGCs and metal raceways.

## Worked example: why the bond trips the breaker

A 120 V circuit on a 20 A breaker feeds a metal-cased appliance. A loose hot wire touches the case.

- **With a good EGC:** the fault path (hot conductor, case, EGC, back to the service, neutral, transformer) has very low impedance, say 0.2 Ω total. The current is about 120 / 0.2 = 600 A, and the breaker trips almost instantly.
- **With only a ground rod (no EGC):** the path goes through the earth, which might be 25 Ω or more between the rod and the utility's ground. The current is about 120 / 25 = 4.8 A. The breaker never trips, and the case sits at a dangerous voltage until someone touches it.

That difference is the reason the NEC requires an effective ground-fault current path.

## Sizing (where to look)

You will meet two sizing tables in Article 250:

- The **grounding electrode conductor** is sized from the size of the service-entrance conductors.
- The **equipment grounding conductor** is sized from the rating of the **overcurrent device** protecting the circuit (Table 250.122), and is increased if the ungrounded conductors are increased, for example for voltage drop.

Look up the values in your code book; do not memorise them from videos.

## Common mistakes

- Believing the ground rod clears faults.
- Bonding neutral and ground in a subpanel.
- Calling the neutral "the ground".
- Relying on a metal water pipe alone as the only electrode.
- Forgetting to bond metal piping systems and structural metal that may become energised.
- Sizing the EGC from the conductor size instead of the overcurrent device.

## Quick recap

Grounding connects the system to earth to handle lightning, surges and stabilise voltage. Bonding ties metal parts together into a low-impedance path so faults trip the breaker. Neutral and ground join once, at the service, through the main bonding jumper. EGCs run with every circuit and are sized from the overcurrent device. Check Article 250 in your adopted edition ([NFPA 70](https://www.nfpa.org/70); checked on 2026-10-23).


Explain the difference between grounding and bonding and why the fault path, not the earth, trips the breaker.

Grounding and bonding

Grounding Versus Bonding (26min:26sec)

## Why it matters

Two small devices prevent a large share of electrical deaths and fires in homes. A **GFCI** (ground-fault circuit interrupter) protects people from shock. An **AFCI** (arc-fault circuit interrupter) protects buildings from fires started by arcing wires. The NEC has steadily expanded where each is required, and knowing those locations is a core skill for residential electricians and a regular exam topic.

> **Awareness level only.** Installing, testing or replacing GFCI and AFCI devices on real circuits is electrical work. Do it only under a licensed electrician's supervision with employer training. Pressing the TEST button on an existing GFCI receptacle at home is the only thing a non-electrician should do.

## How a GFCI works

A GFCI compares the current going out on the hot conductor with the current coming back on the neutral. Normally they are equal. If some current returns by another path (through water, a metal pipe or a person), the two no longer match. When the difference reaches about **4 to 6 mA**, the GFCI opens the circuit in a fraction of a second, fast enough to prevent a fatal shock in most cases.

Points to remember:

- A GFCI does **not** need an equipment grounding conductor to protect people. That is why the code allows a GFCI as a fix for replacing ungrounded two-prong receptacles (marked "No Equipment Ground").
- A GFCI does **not** protect against a hot-to-neutral short or an overload; the breaker does that.
- GFCI protection can come from a GFCI receptacle (protecting itself and the downstream "load" receptacles), a GFCI breaker or a dead-front device.

## How an AFCI works

An AFCI watches the current waveform for the signature of a dangerous arc: the irregular, high-frequency noise of a loose connection, a nail through a cable or a damaged cord. Normal arcing from switches and motor brushes looks different and is ignored. When it detects a dangerous arc, it trips. A **combination-type** AFCI detects both series arcs (along one conductor, such as a loose terminal) and parallel arcs (between conductors).

AFCIs are about **fire**, not shock. A GFCI and an AFCI do different jobs, which is why many circuits now need both, often in a single **dual-function** breaker or receptacle.

## Where they are required (dwellings, in general terms)

The exact lists are in **210.8** (GFCI) and **210.12** (AFCI) and they change with almost every edition, so treat the summary below as general awareness and read the sections in your adopted edition.

**GFCI protection** (210.8) in dwellings has long covered receptacles in bathrooms, garages and accessory buildings, outdoors, crawl spaces, unfinished basements, kitchens (now including more than just countertop receptacles), within a set distance of sinks, bathtubs and showers, boathouses and laundry areas. Recent editions extended it to more locations and to some 240 V receptacles and specific appliances. Other articles add their own GFCI rules, for example Article 680 for pools and spas.

**AFCI protection** (210.12) in dwellings covers the 120 V, 15 and 20 A branch circuits supplying outlets and devices in most living areas: kitchens, family and living rooms, bedrooms, dining rooms, closets, hallways, laundry areas and similar rooms. It also applies when existing branch-circuit wiring in those areas is modified, replaced or extended, with some exceptions for short extensions.

Non-dwelling occupancies have their own GFCI lists in 210.8(B).

## Worked example: reading a floor plan

A small house plan shows: kitchen with countertop receptacles and a dishwasher, a bathroom, a bedroom, a hallway, an attached garage and an outdoor receptacle by the back door.

- Kitchen countertop receptacles: **GFCI** and **AFCI** (often a dual-function breaker).
- Dishwasher outlet: **GFCI** in recent editions; AFCI as a kitchen outlet.
- Bathroom receptacle: **GFCI** (bathrooms are generally not on the AFCI list, but check your edition).
- Bedroom and hallway receptacles and lights: **AFCI**.
- Garage receptacles: **GFCI**.
- Outdoor receptacle: **GFCI**, plus the outdoor weather-resistant and in-use cover rules.

Then confirm each against your edition's 210.8 and 210.12 text.

## Testing and nuisance trips

GFCIs and AFCIs have a TEST button; manufacturers recommend testing them monthly. A GFCI that will not reset may be wired with line and load reversed, or protecting a downstream fault. Frequent AFCI trips usually point to a real problem (a loose connection or damaged cable) or, less often, an incompatible appliance. Troubleshooting those circuits is for a qualified electrician.

## Common mistakes

- Thinking a GFCI protects against overloads, or an AFCI against shock.
- Assuming a GFCI requires a ground wire.
- Using an old list of required locations from a previous edition.
- Forgetting that modifying existing circuits can trigger AFCI requirements.

## Quick recap

GFCIs compare outgoing and returning current and trip at a few milliamps to protect people. AFCIs detect dangerous arc signatures to prevent fires. Required locations are in 210.8 and 210.12 and change every edition. More information: [Electrical Safety Foundation (ESFI)](https://www.esfi.org) and [NFPA 70](https://www.nfpa.org/70). Checked on 2026-10-23.


Know how GFCIs and AFCIs work and where the NEC generally requires each in a dwelling.

GFCI and AFCI

GFCI breaker basics - Ground fault circuit interrupter how it works

Where and Why Do We Need AFCI Protection?

## Why it matters

Motors run pumps, fans, compressors, conveyors and almost every machine in a commercial or industrial building. They are also unusual loads: they draw several times their running current when they start, and they can overheat slowly if they are overloaded or a phase is lost. Article 430 handles this by splitting protection into separate jobs, each sized differently. Add the control circuit that starts and stops the motor, drawn as a **ladder diagram**, and you have a topic every electrician uses and every exam tests.

> **Awareness level only.** Motor circuits involve high voltages, stored energy and moving machinery. Working on them requires employer training, lockout/tagout procedures and supervision by a qualified person. This lesson is paper and calculator practice.

## Two different currents

- **Full-load current (FLC) from the code tables** (Article 430's tables by horsepower and voltage) is used to size **conductors**, the **short-circuit and ground-fault protection** and disconnects. This keeps the design independent of which brand of motor is installed later.
- **Full-load amps (FLA) from the motor nameplate** is used to size **overload protection**, because overloads must match the actual motor.

Mixing these up is the most common motor mistake.

## The protection layers

1. **Branch-circuit conductors**: generally at least **125%** of the motor's table FLC (430.22).
2. **Short-circuit and ground-fault protection** (fuses or an inverse-time breaker): sized from a percentage of the FLC in Table 430.52. It must be large enough to let the motor start, because inrush current is high.
3. **Overload protection** (the heaters or electronic overload in the starter): protects the motor and conductors from sustained overcurrent. It is sized from the **nameplate FLA**.
4. **Controller** (the starter or contactor) and **disconnecting means**, sized and located per Article 430.

## Overload sizing (430.32)

For a continuous-duty motor over 1 horsepower, the general rule is:

- **125%** of nameplate FLA for motors with a **service factor of 1.15 or more**, or a **marked temperature rise of 40 °C or less**.
- **115%** of nameplate FLA for all other motors.

If that setting does not let the motor start or carry its load, 430.32(C) allows a higher setting up to a limit. Check your edition for those values.

Worked example: a motor nameplate shows FLA 28 A, service factor 1.15.

```text
service factor 1.15 → 125 %
overload = 28 × 1.25 = 35 A
```

The same motor with service factor 1.0 and temperature rise 50 °C: 28 × 1.15 = 32.2 A.

## Reading a ladder diagram

A **ladder diagram** draws control circuits as horizontal **rungs** between two vertical **rails** (the control power supply, often 120 V or 24 V from a control transformer). Each rung reads left to right: contacts (switches) on the left, an output (a coil or lamp) on the right. The output energises when there is a closed path through the contacts.

The classic **three-wire start/stop** circuit:

```text
L1 ──[ STOP (NC) ]──┬──[ START (NO) ]──┬──( M coil )──[ OL (NC) ]── L2
                    │                  │
                    └────[ M (NO) ]────┘
```

- **STOP** is normally closed (NC): pressing it opens the rung.
- **START** is normally open (NO): pressing it closes the path and energises coil **M** (the motor starter).
- The **M auxiliary contact** in parallel with START closes when M energises. This is the **seal-in** (or holding) contact: when you release START, current flows through it and the motor keeps running.
- The **overload contact (OL)**, normally closed, opens if the overload trips, dropping out the coil.

In logic terms, the coil is on when:

```text
M = STOP not pressed AND OL not tripped AND (START pressed OR M already on)
```

This also gives **low-voltage protection**: if power fails, M drops out, the seal-in opens, and the motor does not restart by itself when power returns. Someone has to press START again. That is a safety feature for machinery.

## Common mistakes

- Sizing overloads from the table FLC or conductors from the nameplate.
- Forgetting the 125% on motor branch-circuit conductors.
- Sizing the short-circuit protection like an overload (the motor would never start).
- Wiring STOP as normally open, or putting the seal-in contact in series instead of in parallel with START.

## Quick recap

Table FLC sizes conductors and short-circuit protection; nameplate FLA sizes overloads: 125% with service factor ≥ 1.15 or temperature rise ≤ 40 °C, otherwise 115%. In a three-wire control circuit, the coil runs when STOP and OL are closed and either START or the seal-in contact is closed. Look up Article 430 in your adopted edition ([NFPA 70](https://www.nfpa.org/70); checked on 2026-10-23).

## Try it

Open the **Do** tab. The ladder-rung simulator is written; you add the overload percentage rule.


Size motor overload protection from the nameplate and read a three-wire start/stop ladder diagram.

Motor circuits and controls

Basic Motor Control: 3 Wire Start Stop Circuit (updated)

Motor Overload Sizing

Sketch (or print) a simple house floor plan with a kitchen, bathroom, two bedrooms, a hallway, a garage and one outdoor receptacle.

On the plan, mark every location that needs GFCI protection, AFCI protection or both, citing 210.8 or 210.12 for each.

Write a rough-in checklist of at least eight items (box fill, cable support and protection, grounds connected, circuit sizes, working space and so on), each with the NEC article or section you would check.

Write a final-inspection checklist of at least six items (covers, GFCI/AFCI tests, panel directory, no open knockouts and so on).

Find your state's journeyman candidate handbook on the licensing board or exam provider's official site. Note the code edition, number of questions, time limit, passing score and allowed materials, with the date you checked.

List the exam's topic areas and mark each as strong, medium or weak for you right now.

Write a 6–10 week study calendar with three or four sessions a week, weak topics first, and a timed practice test every other week.

Pick one calculation topic from this course and write three practice questions of your own, with worked answers.

## Why it matters

Two gates stand between an apprentice and independent work: passing **inspections** on the jobs you help build, and passing the **licensing exam** after your supervised hours. Both reward the same habits: knowing the code book well enough to find answers fast, and checking your work against a list before someone else does. This lesson shows what inspectors look for and how to plan journeyman exam study.

> **Awareness level only.** Nothing on this platform replaces a registered apprenticeship or the supervised field hours your state requires. Inspections are requested by the licensed contractor responsible for the job, and apprentices work under a licensed electrician's supervision.

## What an inspector checks

Inspections are staged so that work is checked before it is covered up.

**Rough-in** (walls open):

- Boxes are the right type and size for their fill and are securely fastened, set to finish flush with the wall surface.
- Cables are supported and secured within the required distances of boxes, protected where they pass through framing near the edge, and not damaged.
- Conductor sizes match the breaker sizes on the plan.
- Equipment grounding conductors are connected together in every box.
- Required receptacle spacing, kitchen and bathroom circuits are in place.
- Working space is clear in front of the panel location.

**Service**: the main bonding jumper, grounding electrode conductor and electrodes, service conductors, clearances and meter base.

**Final** (finished):

- Devices installed, cover plates on, GFCI and AFCI protection where required and tested.
- Panel directory filled in, breakers matching circuit conductors, no open knockouts.
- Smoke alarms and other listed equipment installed per instructions.

Inspectors cite code sections when they fail an item. Learning from correction notices is one of the fastest ways to learn the code.

## The journeyman exam

Requirements vary by state, so check your state licensing board's official site for current rules (checked on 2026-10-23). In general:

- **Eligibility**: documented supervised hours (often around 8,000, typically through a registered apprenticeship of about four to five years; see [Apprenticeship.gov](https://www.apprenticeship.gov)) plus classroom hours.
- **Format**: usually a timed, multiple-choice, **open-book** exam taken at a testing centre run by an exam provider. The candidate handbook lists the code edition, allowed books, whether tabs and highlighting are allowed, and the topic weighting.
- **Content**: code navigation, definitions, calculations (conductor sizing, voltage drop, load calculations, box and conduit fill, motors), grounding and bonding, wiring methods and, in many states, theory and state law.

## How to study

1. **Get the right book.** Buy the edition named in the candidate handbook, not just the newest one. Tab it as the handbook allows.
2. **Learn the index.** Time yourself finding answers. Most questions are findable within about two minutes if you know where to look.
3. **Practise calculations by hand** with the same calculator you will be allowed to bring.
4. **Use timed practice exams.** Track which articles cost you the most time and revisit those.
5. **Make a weekly plan.** For example, six to ten weeks of three or four sessions, one article group per week, with a full practice exam every other week.
6. **Exam day:** answer the quick ones first, flag the long calculations and come back; never leave a question blank if there is no penalty for guessing (check the handbook).

## Worked example: a study week

Week 4 (calculations):

- Monday: conductor ampacity and derating, 20 practice questions.
- Wednesday: voltage drop and conduit fill, 20 questions.
- Friday: dwelling load calculation, two full worked problems.
- Sunday: 50-question timed mixed set; log every miss with the section number.

## Common mistakes

- Studying from an edition that does not match the exam.
- Reading the code cover to cover instead of practising finding things.
- Ignoring the state law and business portion of the exam.
- Treating failed inspections as personal rather than as free lessons.

## Quick recap

Inspections happen at rough-in, service and final, and check what will be hidden before it is hidden. The journeyman exam is usually open book and timed, so speed with the index and the calculations matters most. Check eligibility, edition and allowed materials on your state board's site and the candidate handbook, and plan steady weekly study.

## Try it

Open the **Do** tab and build an inspection checklist and a personal exam study plan on paper.


Know what inspectors check at each stage and plan your journeyman exam study.

Inspections and the licensing exam

How to Conduct a Rough Electrical Inspection | This Old House

How To Study For and PASS Your Electrician Exam (FIRST TIME)

Grounding and bonding, GFCI and AFCI protection, motor circuits and control ladder diagrams, inspections and journeyman exam preparation.