Diagram electrical wiring

Here you’ll find home electrical wiring diagrams, wiring photos and many illustrations related to residential wiring. Home wiring consists of a lot of different wire sizes, cables, breakers, switches, and outlets.

We’ll take it a step at a time and make residential wiring completely understandable. The most important thing to observe about electrical installations is safety. Never work on energized circuits. It’s always a good idea when working on an energized system to put some red electrical tape over the breaker switch when it’s in the off position. (Just in case another person animal or such decides to throw the switch while you are working on that circuit)

Home electrical wiring covers a lot of different things such as the breaker box panel, home lighting, appliances and other high voltage electrical systems. Circuit runs and how to use Romex cable for lights and outlets are also included.

It also covers low voltage systems like phone systems, doorbells, computer networks and home security systems as part of the wiring process.

I got my electrical training as an apprentice because I wanted to become an electrician.

Later I learned about electric theory from a technical college as I applied it to telecommunications and residential electrical wiring.
I went into electronics training because I was tired of working outside in the harsh weather. My very first job after trade school was a cozy indoor job working on computer networking

communication lines. According to my luck, that same job switched from T1 data lines to satellite wireless systems and I found myself working on the roof tops out in the cold again for another 11 years.

Anyway, that’s the life of electrical technicians.

From start to finish, I will address the Electrical installation in its many aspects and components, starting with wiring the service entrance.

Then I’ll give a breakdown on cables and wiring for a better understanding of how electricity is used. It’s also necessary to have a good understanding of breakers and fuses to prevent overloads.

Simple lighting circuits are easy to install, yet still need a small level of skill. Complex lighting circuits take a little head-scratching to figure out, but I’ve made some good diagrams of these.

The big bad boys that need special attention are the dedicated high-voltage circuits. These need to be done correctly.

Next on the list is phone and doorbell wiring. This is easy and fun. Every home needs to have computer network wiring to connect to all computers in your home and to prevent spying from nosy neighbors because you thought wireless was a good idea. Finally, all homes should have Cable and satellite TV wiring just to be prepared for the future.

We’ll start off with some terminology. We used to refer to electrical circuits as 110-volts and 220-volts. We now refer to them as 120-volts and 240-volts. The actual voltage is right around 119-volts. This varies from place to place, but you might still hear it referred to as 110-volts. Many wiring circuit labels and electricians still use this term.

electrical blueprint

Don’t worry, some people can’t let go of the past. For us modern folk, it’s 120-volt circuits. A 240-volt diagram electrical wiring circuit is just two 120-volt circuits put together for that extra bit of umph! Ovens, water heaters, clothes dryers, and HVAC(heating, venting, and air-conditioning)systems need a little extra voltage, so we give them two hot lines instead of one. I’ll go over it a little at a time.
We do most of the work with non-metallic sheathed cable, but I’m just going to refer to it as Romex. Almost every electrical contractor uses this term. Romex comes in different sizes and kinds for special uses. The type of wire is marked on both the cable and the box it comes in.

For example “12-2” first describes the thickness of the wire, being 12-gauge wire. The “2” says there are 2 service wires inside. That is a hot(black) wire and a neutral(white) wire. There is also a bare copper ground wire. I know that makes three wires in total, but the ground doesn’t count. Why not? I don’t know! We all just kind of go along with that one.

So, “12-3” says there is three wires in there. There is an extra hot(red) wire for three-way switches, or light duty 220 volt applications. I’ll go over that too. See the pics. Most electrical wiring circuits don’t say Romex on the cables, don’t worry about it. It’s a common term at electric supply places.

Electrical cable

The gauge tells how thick the wire is. The lower the gauge, the thicker the wire. Naturally, thicker, heavier wire can tolerate more electrical current without getting too hot. One way to perhaps simplify ones understanding of wiring is to compare it with water piping (sounds nuts). The bigger the pipe size the the more volume of water can be pushed through it. So the demand is what determines the pipe size, or wire gauge in the case of electrical feeds. Most circuits usually won’t have the type and size of cable listed.

Since most outlet and lighting circuits use 15amp breakers 14-2G cable is generally used with a limited # of outlets or lights per circuit.(Check local codes).14-2 is cheaper and much easier to pull through studs and around corners. If a higher draw (20 Amps) is required such as Kitchen, motor circuits, workshop, Etc. 12-2 cable should be used. Keep in mind that motor circuits- (dishwasher,disposal,furnace) should be on their own dedicated circuits due to the high draw of a motor at start-up.

House wiring cable

diagram electrical wiring

Let’s begin the actual work by putting electrical boxes in wherever there will be a single light switch, an outlet, a phone jack, or a data port. Light switches that have more than one switch will require a bigger box.

These are some of the box types you can use. Some locations won’t let you use plastic boxes. The places where you get electric supplies can usually tell you the code for the boxes.

electric boxes

Once all the boxes are in place, you can start running cable. You will need to have the cables run from box to box before your first Electrical inspection. Many inspectors like to see the boxes “Made-Up” (pigtailing W/wire nuts), at this point all the wires should be run and the wiring inspected before the drywall goes on. Romex should be stapled to the stud within 6″ of the box. The experienced electrical contractor will have the work inspected before the sheetrock goes on.

For lights and receptacles, you can use 12-2 Romex for the electrical. Some locations still allow 14-2 Romex, but I think that is no longer adequate for an electric supply. Any well thought out and properly diagrammed electrical wiring
should have adequate wiring for future expansion. Fifty years ago, who knew we would need so many outlets. With computers, stereos, TV’s, games and sound systems, we need at least ten times more outlets now than we did then. Who knows what the future will be like, but I imagine there will be even more gadgets to plug in.


Most outlet receptacles have four terminal screws, two on each side, two neutral and two hot. They are wired so that the circuit is continuous.

A more practical method in wiring receptacles is called “pigtailing”. Pigtailing uses wire nuts to consolidate wires so that only one wire goes to each terminal. This is especially necessary in Ground Fault Interrupter Circuits. Some jurisdictions will not allow using the outlet as a feed through, thus pigtailing is a requirement in these areas.

Electrical connections

Pigtailing, for example, takes both ends of the neutral wire(incoming and outgoing) and joins them both together along with a third white wire that goes to the terminal. You will do this with the black wire and the copper wire also in plastic boxes. The experienced electrical contractor uses pigtails a lot.

We’ll do a simple light circuit next. The Romex comes from the circuit to the light first, then on to the switch. This is how it looks. Keep in mind that there are several ways of running circuits. This is just one way. This is part of a clean electrical diagram.

coded neutral wire

This is one of those cases where you are allowed to code white wires as hot by putting black tape on both ends of the wire. Some locations require 3-wire cable that has a red cable so there are 2 hot wires.

Speaking of 3-wire cable, Romex 12-3 has a black wire for hot, a red wire called a traveler wire designated as hot also, and a white wire for neutral.

This is handy in 3-way switches.

You will use 10-3 Romex on certain other circuits. There might be other code requirements so ask your inspector before putting in wires.

The water heater will be a dedicated circuit on a 30-Amp breaker with 10-3 Romex in most cases. This will be hard-wired, meaning it doesn’t have an outlet receptacle like the dryer and oven do. It will have a cable that comes out of the wall surrounded in conduit and goes into the water heater to be connected inside.

The clothes dryer will also be on a dedicated 30-Amp circuit with 10-3 Romex.

The Oven/range will be the electrical big bad boy on the dedicated 50-Amp breaker using range cable. This is a special cable made for this purpose. What it usually is, is a big gnarl y cable that has two 6-gauge cables, one 8-gauge neutral, and an 8-gauge copper ground inside.

Our residential electrical plan will include all details of each circuit. All the circuits will start at the breaker box. Let’s go there now.

Click to Enlarge

3-way wiring
breaker box
Service entry

3-way diagram
–Breaker Box–
Service Entrance

The type of breaker box is the choice of the electrical contractor and the local codes, but most codes state that the electric supply and the breaker box be a 200-Amp service with at least 30 breakers.

200-Amps is good enough for the current needs, but 30 breaker slots is too few for modern houses. You should have at least 40 slots.

breaker panel

The inspector will have several requirements about using only GFCI’s in the kitchen area, bathrooms, and outside outlets.

There will also be code requirements about dedicated circuits, a minimum number of kitchen circuits, minimum of outlets on each wall, and many others that might seem overwhelming at first. Once it is all done though, you’ll really be glad you followed all the regs. It makes a better house anyway.

Wiring the service entrance
Cables and wiring
Breakers and fuses
Simple lighting circuits
Complex lighting circuits
Dedicated high voltage circuits
Phone and doorbell wiring
Computer network wiring
Home computer networking basics
Cable and satellite TV wiring
Home electrical wiring blueprint

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