Household Wiring Basics
Electrical Safety Rules of Thumb
Given the dangers involved with electricity, it is hard not to start this hub without stating the obvious. Electricity is dangerous and certain rules must be followed when working with electricity. This hub is not intended to qualify anyone to work with electricity and in doing so, you are warned that working with electricity is at your own risk. This information is intended to educate you on some basic electrical theory, terminology and understanding of an electrical circuit so that you can be more aware and knowledgeable when speaking about your electrical service and repairs. With that said, here are some basic rules that are followed when people work with electrical circuits.
- Never work on a live electrical circuit.
- Always shut of power at the source when working on an electrical circuit.
- Even when you believe the power to a circuit is off, be sure to test the circuit with a voltmeter before being confident that this is the case.
- Notify everyone who is on site that you are working on the circuit and use a lockout/tag-out kit to avoid anyone turning the power on unknowingly of the situation.
- Use tools with insulated handles to help avoid injury from incidental contact with live wiring.
- Never work on an electrical circuit without an escape path, meaning a place where you could be pinned in and cannot break contact with the circuit in the event of electrocution.
Of course there are many things that must be considered when it comes to safety but this will get us started.
Source, Line and LoadClick thumbnail to view full-size
The 3 Parts of a Complete Circuit
Whether it's household or not, electricity needs 3 things to complete a circuit.
- A source: The source can be anything from the power plant to a battery to a generator. Where ever the electricity is coming from is the source.
- A path: The path is usually (almost always) an insulated wire made of copper or aluminum.
- A load: The load is whatever is using the power such as a light bulb, a fan, a refrigerator, etc... Basically anything that is wired or plugged in is your load.
Without a load, the power source is directly connected to the neutral side of the circuit and this is what we call a short circuit.
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How Your House is Wired: Parallel and Series Circuits
Homes are wired in parallel so that the different electrically operated parts of your home can function independently. Picture a ladder where one side of the ladder (black wire) supplies an equal amount of voltage to the rungs (where the loads are) and the other side is your neutral (white wire) where everything returns to ground. If rung #3 is off or broken, the other rungs will still be able to operate.
Otherwise, if our homes were wired in series, which is more like a loop than a ladder, you would perhaps have to turn on the light switch in the kitchen in order to get power to the bathroom and then the bathroom light on to get power to the bedroom and so on. This would be considered a series circuit. Voltage here would drop every time it passed through a load but the amperage would remain the same throughout the circuit.
Common Voltages in Household Wiring
Nearly everything in an American home is wired to a 120V circuit. This means that 120V is supplied to a load and 0V is "taken away". This is why when measuring voltage, your meter says there is 120V present because it is reading the difference in voltage from one side of the load to the other. If you were to put both leads of an voltmeter on the same side of the circuit (both on black or both on white) you would get a reading of zero. Again, most of our house runs on 120V circuits with the exception of a few appliances that may require more.
A residential air conditioning system is one example of an "appliance" that runs on 240V. An electric dryer is another example. In this case, there are 2 power legs (usually red and black wires) that feed the load thus doubling the power.
Side Note: Once 120 or 240V are received by whatever apparatus is plugged or wired in, 24V is typically what makes all the little gadgets or components inside of the product work. A circuit board of some sort in conjunction with a step-down transformer turns 120V into 24V and uses that to make things tick.
Commonly Used Materials in Household Electrical Systems
Of course wire is ran throughout nearly every knook and cranny of our home but not all wires are the same. Most 120V circuits are ran on 12 or 14 gauge wire that is referred to as 12/2 or 14/2. The 12 or 14 refers to the thickness or gauge of a wire. The /2 refers to how many wires are in the insulation that you see.
NOTE: What's funny here is that when you buy 12/2, there are actually 3 wires. The ground doesn't get counted in the /2 number, only the black and white.
In a 240V circuit, it is common that you will see 10/3 wire being used. The 10 actually shows that the wire is thicker and the /3 shows that there are black, red and white wires to use plus you will have a ground wire. Yes, you got it right...the smaller the number, the thicker the wire. 10 wire is noticeably thicker than 12 wire and 12 noticeably thicker than 14 and so on. Metal is also this way. 24 gauge metal is much thicker than 30 gauge metal.
Of course beyond the wires, your system consists of various switches, outlets and junction boxes. Here is a list and some photos to help you understand some of the terminology associated with these items so when you go to the hardware store and they say "did you want a single gang or double gang?", you won't wonder what "sign you should be throwin' down."
Electrical Product Examples
3 Prong Duplex
New Work / Old Work
Electrical Product PhotosClick thumbnail to view full-size
Learning About Electricity
Learning about electricity may not sound like a lot of fun but if you're a bit of a mad scientist like me, it really is quite fascinating. The information I've shared here is just an ounce of what there is to know about how electricity works, where it comes from and what is used to control and distribute this energy.
I hope you've learned something more than you knew when you started reading this hub and perhaps will dazzle your hardware store clerk with your new found knowledge of his department.
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