I have an electric garden tractor made by GE back in the 70’s. It has six – 6V golf cart batteries wired in series to make a 36V system. While this isn’t a high voltage the amount of current that they can produce can be dangerous. In this case the sheet of metal you see carries all the current for the drive motor and the connection on the lower end corroded. This raised the resistance which caused sparking strong enough to blow away metal (see top picture) and even caused the metal to glow red.
Current is what is needed to weld metal in an arc welder. Batteries can provide a lot of current for a short period of time. When working around car sized batteries be careful that your wrench doesn’t connect across something connected to the positive side to the car frame, which is connected to the negative side. This is a particular risk when dealing with the starter, it has a thick cable running directly to the battery. If while removing that cable your metal wrench touches almost any exposed metal you will be creating sparks and possibly ruining some cabling, your wrench, burning yourself or starting a fire.
An old saying from my electrics teacher is “It’s the volts that jolts, but the mills (amps, current) that kills. Just because something like a 12V-36V will not shock you, doesn’t mean it wont cause considerable damage once that current gets flowing through something with less resistance than your body.
Most if not all of us have our houses wired for electricity and with some basic understanding it can remove some of the mystery that surrounds it. This write-up will be focused on how things are done in the US. The principles will transfer to other countries, but the details will be different. Also it is important to note this is not enough information to qualify you to start poking around in the electrical circuits in your house.
In the united states residential electrical service brings 240 volts to the house with the capacity of somewhere between 100 to 400 amps. Think of voltage as the pressure and amps (also called current) as the amount of electricity. This service is connected to a distribution panel that has circuit breakers that provide electricity to all the circuits in the house. Most of these circuits are 15 amps and 120 volts. Kitchens and bathrooms will have 20 amp, 120 volt circuits due to the fact that they usually have devices that draw more current like blow driers, curling irons, toasters and microwaves. High power devices like electric ranges and electric clothes driers require dedicated circuits of 240 volts.
The service coming into the house has two legs and a common. The voltage between the two legs is 240 volts and between either leg and the common is 120 volts. Your service panel will split this 240 volts between two sides of 120 volts each. If you need 240 volts the circuit breaker will bridge between both sides to get 240 volts. A good electrician will try to balance the loads between these two sides, you should never see most of the breakers on one side of the service.
The way a house is wired the “common” or “neutral” is the white wire and it should never be run through a switch. It is electrically the same as the ground wire. If you open up your service panel you will see all the white wires and bare wire attached to a common bus (usually a copper bar with screw terminals). The bare wire braid coming into the house will also be attached to this.
Each circuit is a black wire and it is attached to a circuit breaker that limits the amount of current that can flow into the wire. The gauge of the wire (how thick it is) determines how much current it can safely handle and if it is exceeded the breaker trips and shuts off the circuit. This can happen if you turn on too many thing on the same circuit or if some kind of fault happens in the wiring. If the breaker doesn’t protect the circuit the wiring could overheat and cause a fire.
Further anyplace there is the chance of water being near the plug you will need to have the circuit going through a Ground Fault Circuit Interrupt (GFCI). This will either be the first plug-in the circuit in the wet area (which will protect all the plugs that come after it) or the breaker itself can have the GFCI protection. This device monitors the current flowing on each side of the circuit and if there is a difference it will trip and cut off the electricity. This fault conditions occurs when the electricity finds another path to ground, which is almost universally bad and this device protects you from a getting a shock.
The standard convention in the us is that 14 gauge wire that handles 15 amps is in a white sheath of insulation, yellow if for 20 amp circuits and orange is for 30 amp circuits. You will see this wire denoted as:
- 14-2 which is 14 gauge wire with 2 insulated wires(colored white and black) and a bare ground wire.
- 14-3 which is 14 gauge wire with 3 insulated wires (colored white, black and red) and a bare ground wire. This is used for 3 and 4 way switched circuits.
- 12-2 which is same as 14-2 except the wire is thicker 12 gauge.
- And so on
Note that electricity can kill you and this is intended for information purposes only. You need to know a lot more that is described here before you start messing around with the electrical circuits in your house.
Electrical circuits are a mystery to many people and to be fair even household current can kill you, so unless you know what you are doing you might want to leave any electrical work on your house to a professional. However I firmly believe that everyone should know that basics about as many things as possible and with a basic electrical tester you can know if there are faults in household wiring that require someone with expertise to look at it. While I will not go into electrical theory and standards in this post, a simple tester like the one shown below will really tell you a lot. These are available at any hardware or box store like Home Depot or Menard’s and from Amazon and are in the $10-$15 range. By looking at the pattern of lights it will show you five different wiring faults as well as a correctly wired outlet socket. Further pressing the button will create a ground fault that should trip your GFCI protection. All plugs in wet areas (kitchen, bathroom outside…) should be GFCI protected. After the test make sure you reset your GFCI circuit which can be either the button in the center of the plug or could be in your circuit breaker box depending on the type your home has.
While this is certainly not an exhaustive test as it will not check voltage levels or tell you the size of a circuit, for basic circuit testing it is too cheep and easy to use for everyone not to have at least one. Further if you are having trouble with an electrical device it is good to make sure the plug is wired correctly. That way you will know if you need take the device in for service or have the house wiring looked at. The biggest thing this does for a novice is tell you if the power is on to a plug and if it is wired correctly or if there is a problem. Also it is safe for anyone to use because you don’t have to take anything apart to do the test, you just plug it in like anything else and look at what lights are on and compare it to the code printed on the unit.
Basic Circuit Tester
After reading an article in last months Back Home Magazine about re-using dead drill batteries, I decided to try it for myself. Cordless drills are the great, but if you are unable to recharge them due to a loss of power or you are too far from an electrical outlet, you’re out of luck.
Taking a junk battery that no longer works, I’ve given it a cord, perfect for attaching to your 4wheeler or car battery. This battery no longer works. It’s worn out and can’t hold a charge.
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