Electrical Wiring for Homes & Other Buildings
What You Will Be Doing
This section will help you discover how easy it is for you as a
do-it-yourself to work with the 110/120 volt electrical system
found in your own home. 110/120 volt is relatively simple to wire and
connect and does not require a lot of special equipment or handling.
Electricity can be an intimidating concept for many because of the
potential danger. You can virtually eliminate that danger with a
little knowledge and proper safety practices. However, regardless of
how much knowledge you have, never become lax in dealing with an
electrical system, or it can be deadly.
The information in this section is meant to give you an
understanding of several common electrical situations that you might
encounter. Because of the many options and variations in this area, it
is not intended to be a complete guide to electrical work.
Never take chances with electrical work If you feel you need more
information, consult an electrician or a more detailed reference book
if you plan any extensive electrical work, or to evaluate the
condition of an older electrical system, I recommend you seek a
Safety is of utmost importance when working with electricity.
Develop safe work habits and stick to them. Be very careful with
electricity. It may be invisible, but it can be dangerous if not
understood and respected.
glasses or goggles should be worn whenever power tools are used,
especially if you wear contact lenses.
sure the power is off at the breaker box before doing any electrical
work in a dean, dry area free from anything wet.
should only be connected at accessible junction boxes. Never splice
wires together and conceal them within a wall without a junction box.
attempt to strip wires with a knife. Aside from endangering your
fingers, you will nick the wire metal, which will create an electrical
fault circuit interrupter out- lets should be used under damp
conditions (basements, bathrooms, out- doors, etc.), as required by
the National Electric Code.
create fire hazards by over- loading an outlet or an extension cord.
electrical shock by mapping and marking your switch and outlet boxes.
Put the map on the door of the main power service panel.
warning message that you are working on the circuit at the service
panel, and tape the circuit breaker in the off position. With a fuse
box, take the fuse out.
change the size of a fuse or breaker in a circuit.
certain your connector is CO/ALR rated when you splice aluminum wire.
If it is marked CU/ALR, use only copper wire. Do not use aluminum wire
with push terminals; use only copper or copper-dad aluminum wire.
correct the problem that caused a fuse or circuit breaker to blow
before replacing the fuse or circuit breaker.
wiring that shows signs of fraying or deterioration.
breaking your knuckles by bracing the powerful right-angle drill so
that it cannot spin around if it gets stuck while drilling.
working with wires or electrical connections, check them with a
voltage tester to be sure they are dead.
Plumbing and gas pipes are often used to ground electrical systems.
Never touch them while working with electricity.
use metal ladders with over- head electricity.
proper protection, take precautions, and plan ahead. Never by-pass
safety to save money or to rush a project
. Measures the number of electrically charged particles that flow past
a given point on a circuit (per second).
box (breaker panel).
Houses the circuit breakers or fuses, distributes power to various
parts of your house.
All wiring controlled by one fuse or circuit breaker.
Protective device for each circuit, which automatically cuts off power
from the main breaker in the event of an overload or short. Only a
regulated amount of current can pass through the breaker before it
A long, flexible metal strip with a formed hook (to which you fasten
the cable) or wire to pull through walls, raceway, or conduit.
Turns the power entering your home through the breaker box on or off.
This is sometimes found in the breaker box, or it may be in a separate
box and at another location.
The bar to which the neutral wire is connected in the breaker box.
Placement of outlets, switches and lights prior to actual electrical
Measures the current pressure at receptacles and lights. Average
household voltage is 120.
The rate at which an electrical device (light bulb, appliance, etc.)
consumes energy Watts=volts x amps.
You Will Need
The time needed will depend on the scope of the project.
There are some special (although inexpensive) tools required for use
Long-nose (needle-nose) pliers
Right-angle drill, which can be rented.
Other tools from
your household toolbox
Safety glasses or goggles
Materials . Depending on the extent of wiring you will be undertaking, your list
may include these materials:
Various junction boxes
Horseshoe nails (electrical staples)
lights and fittings
Waterproof junction boxes
Ground fault interrupters
Finding the Hot Wire - Safely
In order to do even the most basic repairs or improvements to your
electrical system, you may need to find and isolate the hot wire.
Here's what you need to know to do that safely.
circuit consists of loads - lights, stereos, receptacles, stereos,
TVs, computers, electric ranges, etc - and line feeds. A
line feed is the set of conductors, and the potential on those
conductors, coming to a device - such as a receptacle or a switch -
from the over current protection device for that circuit.
In simpler words,
it is the wires that feed from your panel into the box you're working
in, and the current that those wires can carry, from the circuit
breaker or fuse in the main electrical panel to the box you're working
in. The line feed, therefore, contains the "hot" wire for the circuit.
The hot wire in any
electrical circuit is that conductor which can only be de-energized by
opening the over current protection device. In other words, if you
remove every device in an electrical box and undo every splice, there
will then be one and only one wire which has current on it in that
box, per circuit, when all of the circuit breakers are on or all of
the fuses are in place. I said "per circuit" because more than one
circuit may feed any given box. This is very rarely done. If you
encounter it, you should almost certainly stop work immediately and
call a licensed professional electrician.
To get back to the
topic. There may be another box, or several boxes, between where you
are and the panel. That's OK. The line feed is still that wire which
can only be de-energized by opening the over current protection
device, plus two other wires in the cable or conduit with it - its
neutral conductor and the ground wire. Here's how you can safely
determine which of those forty-'eleven wires you're staring at is the
Determine Which Circuit You Have
Take off the cover
plate and look on the back of it. If your house has been well mapped,
you may find a note there telling you the circuit number. If so,
great. Go turn the power off at the panel and move on to the next
step. Not so lucky? That's OK. Just plug the transmitter part of your
circuit tracer into the receptacle or into the adapter you've screwed
into the lamp socket, take the receiver to the panel and check each
breaker or fuse for the tone from the transmitter.
If you don't have a
circuit tracer but you do have someone to help you, you can plug in a
lamp and ask your helper to yell when the light goes off. Go flip the
breakers off and back on until you hear a yell. If you don't have a
circuit tracer or a helper, you can plug in a radio. Turn it up until
it's loud enough to hear from the panel. Go flip the breakers off and
back on until you hear silence.
Leave the power to
the box you are working in OFF. Go back to the box and unscrew
the devices. Take hold of them by their mounting ears - the flanges at
each end that the mounting screws went through - and pull them
If you're working
on a standard single-pole switch, there will be two power wires
attached to it. Take both of them off the switch, bend and straighten
them until they point up and aren't touching anything, not even each
other. Put a small wire nut on the end of each one to cover the bare
f you're working on
a receptacle, there will be one or more power wires and one or more
neutral wires attached to it. Take all of the power wires off the
receptacle, bend and straighten them until they point up and aren't
touching anything, not even each other. Put a small wire nut on the
end of each one to cover the bare wire.
Residential power wires should be black or, sometimes, red. On a
properly wired receptacle, they will be attached to brass-colored
screws, or pushed into quick-connect holes, adjacent to the smaller
slots in the face of the receptacle - the ones counter-clockwise from
the ground slots.
To release a wire that has been inserted into a quick-connect hole,
push a small flat-blade screwdriver into the slot next to that hole.
You should only have to push it straight in. Try not to wiggle it
around so you don't break the switch or receptacle.
Energize the Circuit and Test
You've got all the
loose wire ends capped, right? OK, go back to the panel and turn the
power ON to the box you are working in. Then go to the box and
test each power wire with a voltage detector.To get an idea of the way
the voltage detector is used to test each wire, you might want to look
at this short video.
In the example
shown here, there were four power wires - three black and one red. The
red wire brought power from the switch to the receptacle, so that was
definitely not the line feed. That left the three black wires - one
going to the switch box in the same cable as the red wire and two
entering in their own cables. When the tester was turned on and moved
along each wire, it registered power on the one entering in its own
cable from the bottom of the box. That made sense, because the panel
was one level down and there were other lights and receptacles on the
same circuit on the floor above. In the picture above and in the
video, I marked the hot wire by putting a red wire nut on it.
the Circuit and Finish
Go back to the
panel and turn the power to the box you are working in back OFF.
Back at the box,
make the repairs or improvements you had in mind. When you're
finished, you might want to tape around each receptacle and switch
before you put them back in - it reduces the risk of shock to the next
person who opens the box. And now that you know it, write the number
of the circuit on the back of the cover plate.
Put the plate back
on, turn the power on and test your work.
•Glossary of Electrical Terms
•More on Electrical Repairs