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Old 11-23-2011, 10:28 AM   #1
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Trying to understand basic electrical concepts, how was this possible?


Hello,

I am a newer homeowner and a I am trying to learn more about electrical work so I can do some projects around the house. I understand some core concepts of electricity in general but I quickly found when dealing with home wiring there is a lot of new and unknown considerations. I understand pos/nov, circuits, fuses, grounding, wire types and gauges, etc. Now when working with my home wiring I have discovered called a "neutral" wire. I understand hot/ground but I have no idea why this wiring is necessary.

I obviously have a lot to learn. Does anyone know of any good books that where I can learn more about electrical theory and it's PRACTICAL applications. I am more looking for a practical book than anything. Something that will be useful when doing projects around the house.

Some questions... I was wiring up some light kits for my ceiling fans this past weekend. I installed one of them no problem. The next one I had some trouble. After much trouble shooting I found out that the blue hot wire in the ceiling fan was not tied into the ceiling connection when I thought it was. Here is the weird part. Before I knew this I was testing the wires with a multimeter one on the blue wire and the white wire in the fan that is for the light kit. Even though the blue wire was disconnected in the ceiling it was still showing voltage?!? How is this possible. In fact it did not matter which wire I tried as pos they both showed voltage. If the blue wire was disconnected shouldn't this not complete the circuit and there would be no voltage? This really confused me.

Another weird thing I noticed is that I had initially hooked up the light kit and tested the wires with a non-contact voltage tester. Even though the blue wire was disconnected in the ceiling it was showing voltage but only ABOVE the wire nut connection to the light kit on the blue wire. HUH? When I pulled the chain for the light switch it would be gone completely. I'm baffled at this. Why would it stop at the wire nut or better yet why show voltage at all when the blue wire was disconnected.

Any info and advice would be appreciated. I'm sure there are explanations for all of this. Thanks for helping a newbie!

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Old 11-23-2011, 10:56 AM   #2
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Trying to understand basic electrical concepts, how was this possible?


When wiring up household electrical circuits, we always connect up hot and neutral for carrying the power. Ground is connected only to the metal framework of fixtures and appliances. In a sense, for 120 volt circuits you can, if you insist, think of hot (black or red or blue) as "positive" and neutral (correctly must be white) as "negative".

In automotive wiring typically red is hot or positive and black is ground or negative although in some cases negative is not grounded and positive is grounded.

If you connect up the hot wire for the light and forgot to connect the fan/light shared neutral and hot wire for the fan then you can measure voltage at the end of the fan hot wire. This is because enough current can flow fron the light hot wire through the light to the neutral and up through the fan and out the fan hot wire to show up on the meter although not turn on the light. If neutral for the fan unit is connected to the house neutral (cable in the ceiling) then no voltage should be measured on the loose blue wire coming out of the fan unit.

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Last edited by AllanJ; 11-23-2011 at 11:06 AM.
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Old 11-23-2011, 11:15 AM   #3
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Trying to understand basic electrical concepts, how was this possible?


Don't feel bad....we were ALL there at some point in our lives.....at least your honest about your abilities...

Plenty of info in the web and plenty of books out there....you might want to pick up a home wiring guide at one of the big box stores.

Now...wireing....

First off, there is not + or minus in your home wiring. It's all AC....instead you have hot and neutral.

A few quick basics....

Black is always hot (or should be)

White is always neutral. By this I mean it is referenced to earth ground...or should be. In other words, if you grab this wire, you 'should not' get shocked...but don't go doing it to find out. If you look at your standard wall socket, of the two slots, one is longer....that 'should' be your neutral.

If your house is like most houses, you have 3 wires comeing in from the pole. 2 Hots and one neutral. Each hot is 120Vac (give or take a couple of volts). The neutral should be tied to the earth ground in your load center (meter, circuit breaker box).

Important point here...those 2 120Vac lines are 180 deg out of phase with each other. In other words, if you measure from neutral to ether hot...you get 120Vac...but if you measure between the two, you get 240Vac. Inside your load center, each hot get connected to one side of the bus bar. Assuming you have 2 rows of breakers....as you go down each breaker, each one will catch one hot or the other....so if you have a double breaker (one with a rod between the two handles), one side is one of the 120's, the other is the other 120vac....so together, they supply 240Vac...to say your oven. If one side trips, it drags the handle of the other breaker with it.

You will frequently hear the term "Back Stab". This typically is refering to an outlet where the wires are stabbed into the back of it using the spring loaded fingers inside. You will frequently hear us saying "don't do this"...we always prefer to use the side screws.

Now....just a quick note on your lights....

Depending on how your house was wired, your lights could be done one of two ways.....

1. The hot and neutral was ran to the fixture...from there, a back and white are ran down to the light switch. The advantage of this method is that you can run power to a ceiling fan (turn the fan on and off with the pull chain) and still control the lights from the wall.

2. Hot and neut go to the switch...then from the switch up to the fixture....this is nice in that if you want to install occupancy sensor, you have a neut in the switch box....but, if you install a ceiling fan, there is no power for the fan unless the wall switch is on...or you run another hot and neut up there.

Your ceiling fan is going to have 3 wires besides the ground....light, fan and neutral. Unless you have more wires installed, your light and fan wires are going to be connected together.

Now....about that voltage detector.....don't trust them 100%....if it says there is nothing....good chance there is not...but if it says there is? Could be induced voltage....i'm old fashioned....I turn off breakers and use a real volt meter.
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Old 11-23-2011, 11:25 AM   #4
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Trying to understand basic electrical concepts, how was this possible?


Wow thanks for your replies thus far especially yours ddawg16. I love how you explained the entire process of home wiring as it comes in from the pole to the breaker box. I had no idea that 2 120 lines came in from outside, go figure.

One thing you mentioned about the "back stab" outlets. I have replaced several outlets and GFCI's in my home already using these types of connections because they are so easy. I got them at home depot. I have seen the screw down ones as well. Why are these considered an issue? I have no had a problem with them yet. Is it a safety concern?

Thanks!
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Old 11-23-2011, 11:30 AM   #5
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Trying to understand basic electrical concepts, how was this possible?


Not to confuse you but to add to DDawgs - "White is always neutral."

Be careful here. It's better to say "the neutral is always white." White can be used in a "switch loop" situation as in his example #1.

In that case, the white wire is being used as a "hot" - it should be marked at both ends black, and then the (real) black used as a switched hot, back to the light.
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Old 11-23-2011, 11:38 AM   #6
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Trying to understand basic electrical concepts, how was this possible?


I'm not saying your going to have issues....but, when you consider that a majority of your outlets are inline with other outlets....it goes something like this....

You have a romex (that is the sheathed cable that contains the black, white and bare ground) coming from your load center to the first outlet. This romex should be 12-2 (that means 2 12Awg conductors (black & white), not including the ground). This is rated for 20 amps and should be connected to a 20a breaker. 14-2 is rated for 15amps.

From that breaker it goes to the first outlet....so one set of b&w goes on the outlet. You then have another romex connected to the other set of contacts that then goes on to the next outlet....same thing at that outlet....then on to the next.

Now....those back stab connections are only rated for 15A....if you have 12g wire, you should have had a hard time getting those wires in. If it was easy, then you might have 14g wire....make sure the breaker is a 15A breaker.

Lets assume your last outlet on the string has a hair dryer plugged in....and someone else plugs in a vacuum on the next outlet...total load might be less than 20a....not enough to trip the breaker....but, guess what? All of that current is going through the first outlet....those back stab contacts are not really up to a 20A load....you basically have a flat spring loaded blade making contact with a round wire....the surface area of contact is not very large...the tyipcal result is that it starts getting hot....and in some cases starts a fire.

It's a bit hard to explain here....you really need to see a few pics....but I prefer to use a pigtail...that is where I wirenut the connections in the back of the box and have a pigtail coming off that bundle that actually connects to the outlet. The circuit load current bypasses the outlet and it's easier to move the outlet around on a single pigtial versus two sets of 12-2 wire.
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Old 11-23-2011, 12:01 PM   #7
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Trying to understand basic electrical concepts, how was this possible?


So far as books, I picked one for you. This book, from the description, sounds like it would explain the basics. So look for a book with a similar description or get this one...
http://www.buildersbook.com/Merchant...tegory_Code=31

Then I found that book at the following bookstore in the electrical area. There are zillions of books, however many are quite advanced and cover specific things. But here is the link to that...
http://www.buildersbook.com


Alternating Current...
http://en.wikipedia.org/wiki/Alternating_current

Direct Current...
http://en.wikipedia.org/wiki/Direct_current

Then get a "digital multimeter" AND an "analog multimeter".

Digital...



Analog...



Search google.com for the words...

How to use a multimeter

Phantom Voltage
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Old 11-23-2011, 01:31 PM   #8
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Trying to understand basic electrical concepts, how was this possible?


Quote:
Originally Posted by AllanJ View Post
When wiring up household electrical circuits, we always connect up hot and neutral for carrying the power. Ground is connected only to the metal framework of fixtures and appliances. In a sense, for 120 volt circuits you can, if you insist, think of hot (black or red or blue) as "positive" and neutral (correctly must be white) as "negative".

In automotive wiring typically red is hot or positive and black is ground or negative although in some cases negative is not grounded and positive is grounded.

If you connect up the hot wire for the light and forgot to connect the fan/light shared neutral and hot wire for the fan then you can measure voltage at the end of the fan hot wire. This is because enough current can flow fron the light hot wire through the light to the neutral and up through the fan and out the fan hot wire to show up on the meter although not turn on the light. If neutral for the fan unit is connected to the house neutral (cable in the ceiling) then no voltage should be measured on the loose blue wire coming out of the fan unit.
For my part, my electrical experience started with my automotive hobby long before I started working on any house wiring. There is a basic difference between the two worth pointing out, automobiles generally operate on Direct Current (DC) while house wiring operates on Alternating Current (AC).

On the subject of automotive current, I'll speak to Ford since that's what I worked on. The specifics vary by manufacturer, but as far as I know in the late '50's it was standard practice to use 12 volt systems with negative ground in automotive. Up to and including model year 1954, the Ford electrical system in use was a 6 volt system with a positive ground.

Going way beyond what's needed to understand for someone interested in household wiring, 6 volt batteries for cars are a specialty item so it's common to convert to 12 volts. Up to 1954 there wasn't much electronics, so mostly it's a matter of changing light bulbs, the same ignition coil usually is fine you just need to add a ballast resistor, the generator doesn't really need to be changed but the voltage regulator does, and the 6 volt starters usually work fine on 12 volts - better actually since it'll turn the motor over faster for starts. For the radio, where equipped, you need to change the tube that converts DC to AC. The vacuum tube radios actually use AC, which is converted internally from the battery DC.

Anyway, the difference between AC and DC is that DC is generally a constant voltage while AC is actually a wave which viewed on an oscilloscope can be seen to go up and down from a positive to negative voltage.

So with DC electricity, you have a battery that provides basicly a voltage, and you can add more batteries in series to increase the voltage. So if I had 2 6 volt batteries and wanted 12 volts, I connect them in series.

With AC it's not exactly as simple, and this is relevant for the electrical coming into the house and understanding the meaning of neutral and ground. If you operate an appliance plugged into a 120V AC hot and neutral it will get 120 V. You also have appliances such as electric dryers which opperate on 120V AC, and they achieve this voltage by connecting to two 120 V AC hots which are 180 degrees out of phase, so each hot individually is 120 V relative to neutral, but because at a particular moment one has 120 V positive and the other has 120 V negative, together they provide 240 V.

To understand exactly what neutral means, one way of understanding is by explaining how a transformer works. Basicly, the power company has high voltage lines and they connect to one side of a transformer where the high voltage is transformed to the 240 volts that comes into your house. Transformers work by having wire coils which magnetically induce current in another set of wire coils. On the high voltage side, the wire might wrap around 250 times while on the low voltage side it wraps around 10 times. (I might have that backwards, for the sake of illustration let's just go with it. The ratio is 25:1 if the high voltage wire was at 6000 volts and the output is 240 volts.

The neutral basicly connects at the middle of the 240 volt coil, so if there was 10 loops it would connect on the 5th loop.

In theory the ideal state is that half of your house's electrical load is going to be on one of the 120 V phases and the other half is on the opposite phase.

If you think of a clock where the hand rotates once per second, then that's about what the voltage does - where a 120 V hot starts at 120 V positive when it's at 12 o'clock, goes to zero at 3 o'clock, then to negative 120 V at 6 o'clock, then zero at 9 o'clock, then back to positive 120 V at 12 o'clock. That would be one cycle. Household power in America comes in at 60 Hertz (Hz) meaning it cycles 60 times per minute.

So in the ideal state where the two 120 V hots are balanced, the neutral at your outlets is completing the path for the other outlets that are connected to the 120 V hot wire on the opposite phase, and basicly the electricity going into the neutral is cancelling out eachother so there might be zero voltage in the neutral.

At the point where the wires come into the house, neutral and ground are actually connected together. Ground is basicly a safety measure so that if something becomes electrified that is not supposed to, the electricity will return to the transformer through the ground circuit instead of through something that will cause injury or fire.

I've always looked at DC as being more straightforward for understanding it, whether that's just because I learned about it first or because it actually is more straightforward I could not say.
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Old 11-23-2011, 02:26 PM   #9
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Trying to understand basic electrical concepts, how was this possible?


I'm currently reading "Practical Electrical Wiring" by Herbert Richter and Frederic Hartwell. Good book in my opinion

http://www.amazon.com/Practical-Elec...2079855&sr=1-1
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Old 11-23-2011, 03:35 PM   #10
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Trying to understand basic electrical concepts, how was this possible?


Another thing to note as well, i have seen on service calls in the past where half of the house does not work...turns out one of the lines coming from the poco (power company) was dead. Like the poster above me said you will have two 120v lines one of each side of your load center.

When you connect the neutral to the ground it is called "bonding", and you main panel should always be bonded (just a connection between the ground and neutral).

In many old houses you will find the old wiring doesn't even have a ground.

What you were seeing on your meter when testing between the blue wire and the neutral is what another poster mentioned induced voltage, sometimes also referred to as phantom voltage.

Also, you should get in a good practice of testing voltage with ground and not the neutral. Granted they are supposed to be bonded together but i've found many times where i would just get random readings on my meter...

If your ground and neutral is not bonded you will get what is commonly referred to as a "floating neutral".

I've had cabinets installed on DOT projects with floating neutrals where some equipment would work and others wouldn't even turn on.

Somewhere down the line neutral and ground must be bonded. I've had times where my guys ran a hot, neutral, and ground for our power service, all the poco does it bond them as well.


Few things to remember...

If you're unsure about something, ask someone on here...there are plenty of knowledgeable people on here who would love to help with something to you seems very difficult but could be very simple to someone else.

Black -> Gold
White -> Silver
Ground -> Green

Panels are not always labeled correctly! Test with a tweeter or multimeter to make sure the power is off.

If you install a GFI make sure you have your load and line correct.

Kitchens, bathrooms, and GFIs are 12ga wire. Lights can be ran in 14ga.

I'm sure they've come up with a bunch of new codes to drive electricians nuts but that's my basic overview from what i remember back when i was a residential electrician.

Once you get a good understanding of everything it's actually pretty easy and simple when you think about it...it's just the codes that make everything difficult (yeah yeah i know the NEC is there for a reason)
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Old 11-23-2011, 05:47 PM   #11
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Originally Posted by CaptainD51 View Post
I'm currently reading "Practical Electrical Wiring" by Herbert Richter and Frederic Hartwell. Good book in my opinion

http://www.amazon.com/Practical-Elec...2079855&sr=1-1
One of the best reference books on electrical wiring, IMO.
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Old 11-24-2011, 04:05 AM   #12
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Trying to understand basic electrical concepts, how was this possible?


Digital meters and non contact testers can give eronious readings,
Dont rely solely on any one of these.
Use a anologue meter or a good old fashioned test lamp
to double test any thing before you touch it !

ALWAYS ASSUME IT IS LIVE ! UNTIL PROVEN OTHERWISE !
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Old 11-24-2011, 07:00 AM   #13
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Trying to understand basic electrical concepts, how was this possible?


For household wiring, connect a low wattage incandescent test lamp across the same two points where you are touching the meter probes simulataneously and a digital meter will give an accurate reading. Admittedly it can be cumbersome holding everything in place but wires with alligator clips on the ends (can be bought at Radio Shack) can come in handy.

A test light jig with two 120 volt lamps in series will work for both 120 and 240 volt circuits.

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Last edited by AllanJ; 11-24-2011 at 07:03 AM.
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