240 volt circuits

Here is where 220-240 volts starts:



The buss bars in the breaker box are set up to where every other position is a different phase. This means that there are two separate 120 volt power sources coming from the 240 volt breaker.

The small breakers with only one hot lead are called single pole breakers. The ones with two hot leads are double pole breakers.

In a 240 volt circuit is referred to as ungrounded. What that means is, there is no neutral conductor involved. Here is a simple 240 volt circuit:



This diagram shows only the circuit and switches for a 240 volt motor. Only 2 wires of 120 volts are needed. The power comes in through both wires and is neutralized within the motor. Power does not have to travel back through a neutral conductor.

Shown is a perpendicular 240 volt outlet. In reality the motor would be plugged into the outlet with a matching plug. There are several kinds of 220-240 volt outlets and plugs. Here are some.




The 20 amp can be found on some room air conditioners. The 30 amp can be found on clothes dryers. The 40 can be found on some electric ranges.

In some instances the grounding conductor is used as a neutral. I am not sure exactly how this works, but it is allowed. Here is a demonstration:



This is a 220-240 volt clothes dryer. The motor and heat element are 220 volts. The motor control circuit (including the timer) is 120 volts. In some cases there is a 4 wire plug and outlet that utilizes a neutral wire.

This diagram is not correct as shown, but only for demonstration purposes. In reality, there would be switches and the motor control circuit operating the unit.

Each chapter in this series is to give you general information. It is my hope that it will encourage you to learn more about electricity as it can be a most fascinating thing.

The last chapter is a review of the series. I hope you have enjoyed. :)

Parallel Circuits

The wiring in your house is in parallel circuits. Here is another view of the 2 flashlight batteries wired in parallel (discussed earlier):



Let’s start with a description of a duplex outlet receptacle, commonly found in homes:



The neutral screws will be silver colored and the hot screws will be darker (sometimes gold). The grounding screw is green. On a quick-connect, use the holes that are just behind the slots.

Three outlets wired in parallel could look something like this:



Power enters on the black (hot) wire and leaves on the neutral (white) wire. It is important to keep the black (hot) wires to the hot (smaller slot) side of the outlets.

There are two screws on each terminal. They are joined by a tab, as long as the tab is intact; it makes no difference which screw you use on that side. If you break the tab, then the connection between the upper and lower “plug in” will be broken.

You will see why that can be useful a little later. Now let’s talk about switches. For simplicity, I will only mention single pole switches. I will devote a later discussion to other types of switches:




Here is basically what happens in a single pole switch. The two screws are connected
in the “ON” position. The connection is broken in the “OFF” position. The purpose of the single pole switch is to break the connection of the hot conductor. This interrupts the circuit and kills the power.

There are several ways to wire a switch in a 120 volt parallel circuit:



Power going to a switch is called the “feed”. Power going from the switch to a light, outlet, fan, etc. is called the “switch leg”. In this diagram, a switch controls a light. I have not used the ground conductors to keep it simple.

This same switch could just as easily control an outlet. This is often done at room entrances. A lamp can be turned on to light a dark room, upon entry.

The common screw (darker) will stay hot all the time. This is important so, power can be run to something else. If you ran additional things like outlets, from the switch leg side, everything in the circuit would be dead when the switch was “off”.



In this diagram, the light and outlet A are off. Outlet B is live.



In this diagram the switch operates the top plug of the outlet. The bottom remains hot all the time. Notice the tab broken. That separates power from the top and bottom.

At present, the top is dead and the bottom is live. To do this, you must run an extra hot wire. But in some cases, the switch and outlet are in the same box (double gang), so the extra wire need only be a few inches long.

When using switches, the neutral wires will need to be spliced together. The best thing to use is a spring loaded wire nut. They thread on the wires and work very well.



They come in many sizes. There is just the right size for the job you need. If splicing only 2 wires, there is no need to twist them together. Just strip about ½ inch of insulation.



If twisting the wires, you will need to strip quite a bit of insulation, then snip it off even. Make sure you snip enough so bare wire will not be showing, after you have threaded the wire nut on tight.



The green wire nut is for ground connections and no need to worry about bare wire showing.

Next is 240 volt circuits.

Grounding

First we will talk about 120 volt branch circuits in your house, and why they must be grounded. Here is where a circuit originates:



Notice that the neutral wire and grounding wire are connected to the same buss bar.
Let’s follow the power to show you why.



The power comes from the breaker box to a receptacle as shown. When you plug in something like a clock or television, the power goes in through the hot wire, through the appliance and leaves on the neutral wire.

The grounding wire does not normally carry current. But it is needed when you plug in a metal chassis appliance. This could be a computer, refrigerator, or such. The grounding conductor is used to ground appliances for safety. Here is a demonstration:



This is a standard grounding plug with the third “prong”. This prong connects to the metal chassis. This connects the entire appliance to the neutral buss bar, (which connects to the ground) when plugged into a receptacle.



If something goes wrong (like a broken or bare wire) and the power makes it to the chassis, it (or anyone touching it) will become a conductor, unless the chassis is grounded.




If the circuit was not grounded here is the scenario: The electricity enters the black wire and to the chassis (bare wire touching chassis). Instead of going to the motor it now goes to you if you touch the appliance.

You could be injured or killed, depending on your connection to the ground. Here is what happens if the appliance is grounded:




The power enters from the black wire and to the chassis. However, the appliance is grounded by the grounding wire (green). A short circuit will result. Have you ever seen what happens when a live wire is touched to a grounded wire?

There is a loud pop and a great deal of current is used. The current now flows through the green wire and back to the breaker. This huge current rush will trip the breaker and turn off the power to the appliance.

Do you see why it is not a good idea to use one of those 3 prong to 2 prong adapters to plug in a metal appliance? If you do, your appliance will not be grounded.

You may live in an older house without grounded outlets. There are 2 ways to correct that. You can run a ground wire and use a new outlet. Or you can install a GFCI receptacle. The GFCI stands for “ground fault circuit interrupter”. They are also called “shock savers”.

Shock savers monitor the electric current coming and going. If there is a slight difference it will kill the power in a fraction of a second. Your outlet may be grounded, but if you are wet and in a situation to trip the breaker, it may be too late.

It may take the breaker, a second or so to trip. Electricity travels close to the speed of light. It could pass through you many times in one second. The GFCI can be a lifesaver.

GFCI outlets are important to have in bathrooms and kitchens. You should use one anytime there is an outlet within six feet of a water source. They should always be used outside, too.


At a later date I will write a section on installing GFCI outlets. Next is series number 8 "Parallel Circuits".

Electric boxes

There are many type of boxes available. First we will mention outlet boxes. These boxes are rectangular and house receptacles and switches. However, they come in different sizes and makeup.

Single boxes are made of plastic or metal. There are construction types that nail to a stud. These are installed before the wallboard. And there is the cut-in type that you can install afterwards. These will be used if you are installing a new switch or receptacle where there was none before.

And there are ones made specifically for outdoor use. Here are a few examples:


Single wall construction plastic box


Double gang box similar to above


plastic cut-in box (notice the tabs)


Ceiling boxes are made to fasten to the ceiling joists. They also make them in cut-in type, but are not recommended for heavy things like ceiling fans.


Typical ceiling box.

In most simple projects you will not be installing a new box. But knowing what is there will help you to better understand what you are doing.

Now it is time to talk about the importance of grounding. And you will discover what that bare wire is doing in those electric boxes.

Conductors

You will be dealing with wires in your electrical projects. The black, white, and bare wires will be in a flat cable, often referred to as “Romex”. It got the name Romex because of the company that used to be the primary manufacturer of house wiring.

The cable may be different colors, but they are labeled by the wire size and whether there is a ground conductor. I use 12/2 W Ground. This means that there are 2 number 12 conductors (black and white) and a number 12 ground conductor that is bare.

In many cases it is OK to use 14/2 with ground. But you cannot use this for anything other than a 15 amp circuit. The best all around wiring (120 volts) to use is number 12, as it is safer and will handle a 20 amp circuit.



Typical cable with white, black, and bare copper in the middle.

When you are replacing outlets or switches you will encounter wire in cables. In some cases, it may be necessary to strip more insulation from the cable.



This is a simple cable stripper. You place the wire inside and a tab slices the cable.



These are simple wire strippers. Inexpensive and very effective. If you need to strip wires to wrap around a screw terminal, there are a few things to remember.

1. Strip the wire so there is about an inch of conductor showing.
2. Always bend it to the right as shown.
3. Wrap it around the screw
4. Continue as shown and tighten screw as show:



When you wrap the wire to the right the screw will pull it tight. This is due to the right hand threads. Wrap it to the left and the screw will try to pull the wire off of it.

Sometimes you will need to remove wires from a quick connect receptacle or switch. It is quite easy as shown with the back of a receptacle:



There’s really not much to it. If you are replacing a screw terminal outlet with a quick-connect, snip the wire and re-strip about ¼ inch of copper. Many quick-connect outlets show you how much to strip on the back.

If there is not enough wire to snip it, then you will need to straighten out the wire and snip it off till it is about ¼ inch showing.

You will notice that outlets and switches are in boxes. That is the next subject.

From the Meter (Breakers)

Now we will discuss the power as it comes from your electric meter. From the meter it goes into a breaker box, as shown:





The power comes to the breaker box in three wires. Two of the wires are hot with 120 volts. The other wire is neutral and goes to the ground. I have named the phases A (blue) and B (red). This is for demonstration purposes only.

The main breaker will cut off the power to all the other breakers, manually. It will also cut off power if the total amount of current is greater than its value (usually 100 or 200 amps)

Each individual breaker will cut power to each circuit manually. It will cut power when its current value is exceeded. They range from 15 amps to 30 amps usually.

Your 120 volt circuits will only require 1 black wire (hot 120 volt), One neutral wire (white) and one ground wire (usually bare copper).

You may hear of household voltage as 110 volts. That is because the voltage will vary a little from house to house. Most voltage is between 110 and 120 volts.

Your 240 volt circuits (stoves, air conditioners, clothes dryers) will require an extra 120 volt wire (usually red).

These cicuits may be referred to as 220 volts. This is also due to voltage variations.

But let's talk more about breakers. It is important to understand how and why they function. They perform a vital task in protecting you and your loved ones.

The main breaker in your house is either 100 or 200 amp rating. What this means is, if all the circuits in your house are using more than 100 or 200 amps of electric current, the breaker will shut the power off to your house.

Breakers work in a similar fashion to fuses, except they can be reused many times. A fuse has a metal element that can only withstand the heat of so much electricity. If there is too much, the element will melt and break and the power cannot flow through the fuse. Then you must throw away the fuse and get a new one.

Many circuit breakers work on the principle of electromagnetism. The more current that flows through it, the stronger the magnet becomes. At some point there will be enough electricity to trip a very stiff switch. And the power is cut off.

A 30 amp breaker will have a switch twice as hard to trip, than a 15 amp.

Some breakers use two strips of metal that bend under electric current. At some point they will bend enough to throw a switch. The basic principle is the same.

Here are actual pictures of my breaker box:


whole view



main breaker




110-120 volt circuits


220-240 volt circuits

Next we will talk about conductor (wires).

negative and positive

As we discuss the power that gets to your house, it is important to mention polarity. If you look at any flashlight battery you will see a (+) on one end and a (-) on the other.
What exactly does that mean?

In batteries, electricity is made from a chemical reaction. Electricity always flows from
(-) negative to (+) positive. In a flashlight the current flows from the negative terminal and into the positive terminal where it is neutralized. This is how the “juice” in a battery is depleted.

But have you noticed that most flashlights take 2 batteries and they have to be installed in just the right direction? Why is that? In order to understand that, we need to mention parallel and series circuits.

I have used flashlight batteries for our illustrations. They are 1.5 volts, and I am assuming they have one amp of current available for demonstration purposes. The batteries in a flashlight are configured into a series circuit. Notice the configuration:



In a DC (direct current) series circuit, the power is wired negative to positive and positive to negative. In this way, the voltage is doubled and the amount of current (from the batteries) remains the same.

The current goes from the negative end of the bottom battery and through the element of the light bulb. Then from the bulb it goes into the positive terminal of the top battery as it is used.

This series circuit makes one 3 volt, 1 amp battery, from the two 1.5 volt, 1 amp batteries.

We won’t go into AC (alternating current) series circuits, as you will not be encountering them in simple home projects.

Next we have a parallel circuit below:



In a DC (direct current) parallel circuit, the negatives are wired to each other as are the positives. The voltage stays the same, but the available current is doubled.

The current flows from the blue and through the bulb element. Then from the bulb it goes to the red, where it is neutralized.

This series circuit makes one 1.5 volt, 2 amp battery, from the two 1.5 volt, 1 amp batteries.

Here is an illustration of what happens inside the bulb as the
current flows:



You will be encountering AC (alternating current) parallel circuits in your home. There is no true negative or positive as the current continually alternates, but the idea is the same.

You keep the black (hot) wires together. Wire the white (neutral) wires together. And keep the (bare or green) ground wires together. But you must never assume that black wires are always hot as well as the others.

If someone accidentally used the wrong colored wire, you could be in trouble. This usually does not happen. But if you live in an old house it would be worth checking them first. We will cover, checking power a little later.

Next we need to get to the power that is entering your house from the electric meter.