Residential electrical wiring diagrams

Your blueprints come with a house wiring diagram that takes the guess work out of locating circuits and breakers.

Here are some common electrical home wiring diagrams that are used a lot in new home construction. There is also a thorough explanation on cable sizes, breakers, outlets, switches and much more in home wiring.

This mess of wires is comical, but real. You certainly don't want your home wiring to look like this. That's why a good house wiring diagram is necessary to keep it all organized.


Please use caution when working with electricity. There is never any reason to be working on energized circuits!

***Remember, even though the codes I talk about here are from the National Electrical Code book, your local codes take take priority. Your electrical inspector can help you with your local codes.***

Often times I find people who are reluctant to do their own electrical wiring. I always respect that. The truth is that if you or a licensed electrician does the wiring, it still has to be approved by an electrical inspector before the power can be turned on.

I rest well at nights knowing that my electrical wiring was carefully inspected and then approved.

OK, so there's a buttload of stuff to cover on the electrical house-wiring-diagram part of smaller home construction. I'll start off with the basics. At the bottom of this page I will put many links to each aspect of home electrical wiring.

3way switch diagram

Diagrams really help a lot. I will use several examples of house-wiring-diagram illustrations like this one.

Most of the wiring in the home will be simple circuits like lights, switches and outlets. These circuits are usually wired with non-metallic sheathed cable. Most people just call it Romex though.

Black wires are hot lines. Black wires are wired only to hot terminal screws or to other black wires. Red wires are also hot and are usually either a traveler wire (for 3-way switches), or an extra hot 120-volt line to double voltage for a 240-volt appliance or fixture.

Red wires are also only wired to hot terminal screws on outlets or switches and other red and black wires on appliances and fixtures. White wires are neutral wires and are only wired to the neutral bus bar inside service panel, the neutral terminal screws on receptacles, or joined with other white wires.

Bare, copper wires and green wires are ground wires and they attach to other ground wires or can be terminated inside of metal boxes.

There is an exception to the color code rule that should be mentioned. In certain situations, such as 3-way switches and dual control, dual light switches, even 12/3 romex cable falls one wire short of enough hot wires. In this case, it is acceptable to use a white wire as a hot wire, but only if the wire is wrapped with black electrical tape on both ends. This is quite common.

Simple circuits like these use Romex 12-2 and Romex 12-3 cable.

home wiring cable

The number on the cable and on the box will describe the cable. For example, 12-2 means the cable thickness is 12-gauge and there are 2 wires inside. 12-3 means the thickness is 12-gauge, but there are 3 wires inside. By the way, technically there is a ground wire in each, but we don't count that in the description. I truly don't know why.

There are heavier gauge cables that will be used for 240-volt circuits like water heaters, dryers, HVAC systems, and oven\ranges. These house-wiring-diagram circuits need extra power and they each have special cable. They are also on dedicated circuits.

cable sizes

See how the cable sizes differ? The heavier the cable is, the more electrical current it can supply without getting hot.

Another important part of electricity is amperage or just amps. Imagine electricity as a garden hose. The bigger the hose, the more water can be supplied. For electricity, amps is like the amount of water passing through the hose. It's even called current.

Most new homes are now built with a 200-amp breaker box. That basically means that a maximum of 200 amps can be drawn from the power transformer at once, but it isn't very likely that will ever happen.

Even smaller homes need a breaker box with a lot of spaces for breakers. I suggest the minimum size of breaker box would be a 200-amp, 40 slot breaker box.

breaker box diagram

The 240-volt circuits will take up two slots in the breaker box because they use two legs of power. Each leg of power is 120-volts. Residences are supplied with two cables from the electric transformer to the service meter. They then go from the meter to the breaker box.

service panel diagram

I know, my drawing is like a first grader with a dull crayon.

Anyway, the cables that come from the service panel to the breaker box are these heavy, gnarly cables and the gauge is like 2/0 gauge. That's heavy cable!

It's best to let an electrician wire this part after you've installed all circuit runs and after they've been approved by an electrical inspector.

Here is the usual order of the electrical hook-up...

1. Utility company installs a temporary power cable to your building site. You will use this for all framing construction.

2. Once the walls are up you will install the breaker box and make all the circuit runs from the breaker box to each individual electrical box.(light switches, outlets, lights)No switches or outlets will be connected at this point.

3. Electrical inspector will inspect all circuit runs for lights, outlets and all dedicated circuits. He or she will inspect the breaker box for proper procedures and accurate grounding.

4. He or she will approve a full utility hook-up from the service meter to the breaker box. He or she will give permission to sheetrock the walls.

5. Finish the walls and then connect all outlets, switches, appliances and fixtures.

6. Electrical inspector will give it a final inspection and will approve it before an occupancy permit can be obtained.

This is the basic outline of a wiring diagram for smaller homes.

Planning your electrical circuits

Simple electrical circuits

Electrical blueprint symbols

Complex circuits

240-volt circuits

Phone wiring

Doorbell installation