Download 3-Way Switch Protected Under 18 U.S.C. 707

3-Way Switch
Protected Under
18 U.S.C. 707
Lesson Objectives:
This lab is designed to educate the student on basic electrical wiring
practices with hands on participation.
Students will learn how to wire a circuit with the ability to control a
light from two different locations using two 3-way switches. This
is a common electrical circuit used in house wiring and also one that is
commonly misunderstood by the beginner.
The lab will introduce the student to many common electrical devices,
tools, and wire used in house wiring.
The step-by-step slides will help guide the student how to properly
install electrical devices and perform safe wiring connections.
Concepts in brief
AC- Alternating Current. Alternating current means the electrical
source for feeding voltage and electrical power is alternating (or
switching polarity) over and over. This type of electrical power is
in our homes, farms, businesses and industries delivered by a utility
company through a power plant, substations and power poles. DC
electricity is Direct Current and polarity is constant all the time as found
in batteries.
VAC- Volts Alternating Current. Common house voltages are
120VAC from the typical house outlet and 240VAC sometimes
required by air conditioning, heating equipment, ovens, and
water heaters.
House wiring- The electrical wiring, and devices (such as outlets,
switches, plugs, circuit breakers) found in homes, farms, and
businesses that supports electrical power from 120VAC and even
up past 480VAC.
Concepts in brief- continued
Hot- Refers to a conductor carrying voltage. The “live” wire that can cause injury if
not respected! Typically the black and red insulated conductor in house wiring is hot,
but beware a white wire might look neutral and actually it can hot as well. The brass
color screw on outlets, switches and loads are to be connected the hot conductor.
Neutral- Refers to a conductor returning the flow of electricity back to the source
after passing through an electrical load. Typically this the white insulated wire and
neutrals are typically grounded back at the breaker panel. The silver screw is
connected to the neutral conductor.
Ground and grounded- Refers to conductors that are at a 0 volt state connected back
at the electrical source most commonly the breaker panel in a building. Each building
has a rod made of copper buried deep into the earth which all ground conductors are
tied. The main purpose of grounding is safety from electrical shock or fire. If a hot
wire or terminal comes into contact with metal that is properly grounded, two things
will happen: 1) a short circuit will form between hot and the ground conductor tripping
a circuit breaker and stopping the electrical flow and 2) electricity will flow to a
ground state much faster than entering the body preventing a shock. Ground wires are
color coded green or bare copper. All metal electrical devices are to be grounded!
A look at some common electrical devices used in house wiring.
Plug
Brass = Hot = Black wire
Outlet
(Receptacle)
Brass = Hot = Black wire
Long slot = Neutral
Short slot = Hot
2-way switch
3-way switch
Green = Ground
Silver = Neutral = White wire
Ground
A closer look at the 3-way switch
Position Terminal
3-way Switch
Ground
3-way Symbol
Common Terminal
(odd color terminal)
How it works: Flipping the switch up or down makes a closed circuit between
Common (C) to position A or Common to position B. Two 3-way switches are
required to control an electrical load from two locations. See next page…
How it works: Look at the positions of switch 1 and switch 2. Electricity has a complete path
from the plug to the lamp and back to the plug. Rule: The common terminal a 3-way switch
will either be to the hot side of the load or hot side of the voltage source.
How it works: Look at the positions of switch 1 and switch 2. The path of electricity is
broken at switch 2, thus the light is off. What would happen if switch 1 was flipped down?
The 3-way circuit allows control of the lamp from two different locations.
So far…
•We have learned some terminology as it applies to house wiring.
•Looked at some typical electrical devices used in house wiring.
•Learned the meaning of color codes in house wiring.
•Took a close look at the 3-way switch and how it functions in a
circuit.
It’s time to get started and wire a 3-way switch circuit.
Remember safety first! Never plug in a circuit until you have
checked your work and all terminations are done and out of the
way or covered from accidental contact. Have an instructor
check your work before you test!
Unassembled Parts for AC Electricity Course
Common Tools for AC electrical work
A look at one type of wire used in house wiring.
This is often called Romex cable and in this example
the cable is a 2 conductor with a ground wire.
bare copper
(ground)
black
white
Another type of Romex cable. This cable
is a 3 conductor with a ground wire.
black
copper
white
red
BEGIN
Start with the lab board and 5 wire restraint
clamps. Clamps will be installed in the knockout
holes of the 3 metal wire boxes.
Close look at wire restraint installed through knockout hole
To tighten a wire restraint use a flat blade screw driver and force
the locknut of the restraint tight.
Using wire strippers and the 2 conductor wire with ground
remove insulation as shown above.
Strip outer insulation from both ends of the 2 conductor wire
(with copper ground) and thread through wire restraints.
Starting with the AC load (light) octagon box, strip and make loops
on the individual conductors. See following slides for details…
Strip individual wires using strippers. Notice 14 AWG
marking on stripper is used with the 14 gauge wire.
Making loops with needle nose pliers.
Attach copper (grounding) wire to octagon box with green screw.
Attach black (hot) wire to brass terminal of lamp holder. Notice
the loop of the conductor follows the direction of the screw as
it is tightened, this is an important practice to follow.
Attach white (neutral) wire on silver screw of lamp holder
just like the black wire.
Strip insulation from a piece of 3 conductor with ground cable
And route through the switch box that has the 2 conductor cable.
Switch box grounding. Take bare copper wire from each cable
and attach to metal box using green grounding screw.
White wires are stripped, twisted together and a wire nut is
twisted over the bare wires.
The black conductor from the lamp is attached to the
common (odd color) terminal of the 3-way switch. The red and black
from the other cable are attached on the other free terminals.
The lamp and one switch are now completely wired. Now remove the
insulation off the other end of the 3 conductor cable and loop
through wire restraint of the other switch box.
Remove insulation from one end of power cord
and route through remaining wire restraint.
Ground the bare copper from the 3 conductor cable
to metal box using green grounding screw.
Attach power cord ground to remaining 3-way switch green
terminal.
The power cord black wire attaches to the black terminal of the 3-way
switch. The red and black wires from the 3 conductor will attach to the
remaining terminals just like the first switch. White wires are secured
under wire nut.
Remove the insulation from the other end of the power cord
and slide cord through the plug’s hood. Using the picture as a
guide trim back wires for proper length.
Remove insulation from each wire of power cord (just enough
to get under screw). Black wire goes to brass screw, white wire to
to silver screw and green wire to green screw.
Attach plug end to plug hood (tucking wires inside). Push power cord
through hood and secure with hood clamp screws.
After checking your wiring thoroughly, secure the switches, lamp holder
and switch covers to metal boxes with the furnished screws.
switch cover
After securing covers place a good light bulb in lamp holder.
Plug in and test. Either switch should be able to turn the
lamp on and off.