wiring a house fourth edition pdf

The Basics

ot knowing the basics of electricity can get you into
a lot of trouble—painful trouble.

I remember when my
Uncle Bud started teaching me about electricity back in
the 1950s.

I accidentally tripped on some black wires
in the attic and got shocked as I grabbed onto a funny-looking
porcelain knob to stop my fall.

This was my first lesson in basic
wiring: Don’t touch this and don’t trip over that.
Today, the rules are a little more complex than those
by which my Uncle Bud and my Grandfather Bunt worked.
(My Grandfather Bunt didn’t even have a meter to test for voltage.
He used an old-time method that I can’t print here for fear that
somebody might try it and get electrocuted.)

Although they didn’t
have the modern test equipment that we do, they talked the same
electrical language, using terms such as “current flow,” “voltage,”
“power,” and “resistance.

” But I’m sure they didn’t understand
their meanings as well as we do today.

In this chapter, I’ll help
you make sense of the basics of electricity so you understand
what you’ll be doing and why.

How Electricity Flows
Wire works much like a garden hose, but
instead of conveying water, it conveys electricity from one location to another. When you
turn on a hose faucet, water entering from
the spigot pushes on water already in the
hose, which pushes water out the other end.
Electricity flows in much the same way.

An electron flows in one end of the wire, which
knocks an electron, which in turn knocks
another electron, until an electron eventually
comes out the other end

Elements of electricity
Electricity is the organized flow of electrons
along a conductor.

It is generated through heat,
pressure, friction, light, chemical action, or
magnetism. Electricity is a complicated phenomenon, but for an “everyday” understanding,

it’s helpful to know the meaning of these
four terms: voltage, current, resistance, and
power (watts) and their relationship to each
other. Ohm’s Law, a basic principle of electricity,
states that voltage is directly proportional to the
current and resistance.

You can calculate any
one value if the other two are known (E = IR,
where E is the voltage, I is the current, and R is
the resistance).
Voltage is the electrical pressure provided by
a battery or other power source.

The higher
the voltage, the more current the source can
produce.

Voltage is measured in volts; a voltage quantity is always followed by a capital
V or the word “volts” (120V or 120 volts). A
multimeter measures the voltage between two
points on a circuit, or if the current and resistance are known, it can be calculated using
Ohm’s Law.

A Residential Electrical System
The house wiring begins at the service entrance
(SE)(see the drawings on pp. 10–11). In this
section, I want to show you a typical house
wiring system.

I’ll go into more detail about all
these circuits in later chapters.

It’s also impor
Wire Gauges
We use insulated wire or cable to deliver electricity to where we need it. It didn’t take long
to learn that the larger the wire’s diameter, the
more electricity we could deliver to the load
and the less we would waste along the wire.

The American Wire Gauge (AWG) provides
numbers for the different wire diameters.
The larger numbers are used to represent the
smaller wire diameters. For example, a cable
that has a big number, such as 18, has a smaller
diameter than a cable with a small number,
such as 1.

Zero is called “ought”; a cable with
one zero is written as 1/0, or one ought. And
the system doesn’t stop at zero for the largest
diameter cable, either.

No, that would be too
simple. Numbers less than zero identify bigger cables.

What’s less than zero? More zeros.
From 1/0 it goes to 00 (2/0), 000 (3/0), and
0000 (4/0). Each descending number indicates
a larger diameter cable. To make things even
more complicated, the system changes in
midstream. As soon as you get past 4/0 (four
ought), the diameter of the conductor is referenced by its cross-sectional area: 250 kcmil,
300 kcmil, and so on.

What gauge goes where
Service-entrance cable for dwellings has its
own reference in the NEC.

The ever-popular
Table 310-16 gauge finder is fine for everything
except the service entrance and the subpanel
feeder cables.

Copper versus aluminum wiring
When it comes to residential wiring, there
are two standard wire materials: aluminum
and copper. Most homes use copper wiring
for receptacles and switches for good reason.
Small aluminum wires have to be handled very
carefully because they break easily.

And they
must be installed and spliced only with codeapproved materials. Sometimes those materials
are hard to find. For the larger-diameter wires
(6 gauge and up), electricians tend to use both
copper and aluminum.

Aluminum has a slight
cost advantage over copper, and this is more
apparent in the larger-diameter cables.