Your home's plumbing and electrical systems may seem as different as any two things could be. But there are significant parallels. Water enters your home through a pipe under pressure, and, when you turn on a tap, the water flows at a certain rate (gallons per minute). Electricity enters your home through wires, also under pressure (called voltage, measured in volts). When you turn on an electrical device, the electricity flows at a certain rate (current, measured in amperes, or amps).
Unlike water, which is used as it comes from the tap, electricity is meant to do work: It is converted from energy to power, measured in watts. Since household electrical consumption is relatively high, the unit of measure most often used is the kilowatt, which is equal to 1,000 watts. The total amount of electrical energy you use in any period is measured in terms of kilowatt-hours (kwh).
The instrument that records how much electricity you use is called an electric meter. This meter tells the power company how much electricity they need to charge you for. There are two types of electric meters in general use. One type displays a row of small dials on its face with individual indicators. Each meter dial registers the kilowatt-hours of electrical energy. For example, if you leave a 100-watt bulb burning for 10 hours, the meter will register 1 kilowatt-hour (10x100 = 1,000 watt-hours, or 1 kwh). Each dial registers a certain number of kilowatt-hours of electrical energy. From right to left on most meter faces, the far right is the one that counts individual kilowatt-hours from 1 to 10; the next one counts the electricity from 10 to 100 kilowatt-hours; the third dial counts up to 1,000; the fourth counts up to 10,000; and the dial at the extreme left counts kilowatt-hours up to 100,000. If the arrow on a dial is between two numbers, the lower number should always be read.
The second type of electric meter performs the same function, but, instead of having individual dials, it has numerals in slots on the meter face, much like an odometer in a car. This meter is read from left to right, and the numbers indicate total electrical consumption. Some meters also use a multiplying factor -- the number that appears must be multiplied by ten, for instance, for a true figure in kilowatt-hours. Once you know how to read your meter, you can verify the charges on your electric bill and become a better watchdog of electrical energy consumption in your home.
Three main lines (older houses may have two) are responsible for supplying 110-120/220-240 volts AC (alternating current) to your home. The exact voltage varies depending on several external factors. This three-wire system provides you with 110-120-volt power for lighting, receptacles, and small appliances as well as 220-240-volt power for air conditioning, an electric range, a clothes dryer, a water heater, and, in some homes, electric heating.
Electricity enters your home through the power company's service equipment, which is simply a disconnect device mounted in an approved enclosure. It's used to disconnect the service from the interior wiring system. Usually called a main fuse, main breaker, main disconnect, or often just "the main," this disconnect might be a set of pull-out fuses, a circuit breaker, or a large switch.
Although main disconnects can be mounted outdoors in a weatherproof box, they are nearly always inside the house in a large enclosure that also contains the fuses or circuit breakers, which handle the distribution of power throughout the building. This is called a main entrance panel, a main box, or an entrance box. The three wires from the meter enter this box. Two of them -- the heavily insulated black and red lines -- are attached to the tops of a parallel pair of exposed heavy copper bars, called buses, at the center of the box. These two lines are the "live," or "hot," wires. The third wire, generally bare, is the "neutral." It is attached to a separate grounding bar, or bus, that is a silver-color strip in the main box. In most homes this ground bus is actually connected to the ground -- the earth -- by a heavy solid copper wire clamped to a cold water pipe or to an underground bar or plate.
Power is distributed through your house through various electrical circuits that start in the main entrance panel. The 110-120-volt circuits have two conductors -- one neutral (white) wire and one hot (black) wire. The 220-240-volt circuits may have two hot wires alone or a third, neutral wire may be added. In all cases, the hot lines are attached directly to the hot main buses. The neutral wire is always connected to the ground bus and never, under any circumstances, should it pass through a fuse or circuit breaker.
and circuit breakers are safety devices built into your electrical
system. If there were no fuses or circuit breakers and you operated too
many appliances on a single circuit, the cable carrying the power for
that circuit would get extremely hot, short circuit, and possibly start
a fire. To prevent electrical overloads, circuit breakers and fuses are
designed to trip or blow, stopping the flow of current to the
overloaded cable. For example, a 15-ampere circuit breaker should trip
when the current through it exceeds 15 amperes. A 20-ampere fuse should
blow when the current through it exceeds 20 amps. A fuse that blows or
a circuit breaker that trips is not faulty; it is doing its job
properly, indicating that there is trouble somewhere in the circuit. A
blown fuse or tripped circuit breaker usually means there are too many
appliances plugged in to that circuit or some malfunctioning device,
like an appliance with an internal short, is connected to the circuit.
Locate and eliminate the cause of the trouble before replacing a blown
fuse or resetting a tripped circuit breaker.
Caution: Never try to defeat this built-in safety system by replacing a fuse with one of a higher current-carrying capacity. The fuse or circuit breaker capacity should be equal to or less than the current-carrying capacity of the conductors. For example, don't replace a 15-ampere fuse with a 25-ampere fuse. Replace fuses and breakers only with ones of the same size and amperage.
Circuit breakers do not blow like fuses; they are switches that automatically trip open to interrupt the flow of electrical current when it overloads the circuit. To reset a tripped breaker, turn it fully off and then back on.
Branch and Feeder Circuits
Circuits to all the devices in your home that require electrical power start from the fuses or circuit breakers. There are two types of circuits: feeder and branch. Feeder circuits use thicker cables that travel from the main entrance panel to smaller distribution panels called subpanels, or load centers. These auxiliary panels are located in remote parts of a house or in outbuildings, and they are used for redistribution of power, such as in a garage. Feeder circuits aren't found in all houses.
All of the circuits in a home that run from either the main entrance panel or from other smaller panels to the various points of use are branch circuits. For 110-120-volt needs, a circuit branches out through a circuit breaker from one of the main buses and from the ground bus. For 220-240 volts, many circuits use only the two main buses. But all three wires are needed for devices that operate on both 110-120 volts and 220-240 volts.
The 110-120-volt branch circuits go through fuses or breakers, which are labeled either 15 or 20 amps. The 15-amp branches go to ceiling lamps and wall receptacles in rooms where less energy-demanding devices, such as table lamps, are found. The larger 20-amp circuits go to receptacles in the kitchen, dining, and laundry areas where heavy-duty appliances are used.
A 15-amp circuit can handle a total of 1,800 watts, while a 20-amp circuit can handle a total of 2,400 watts, but these figures represent circuits that are fully loaded. In practice, you should limit the load on a 15-amp circuit to no more than 1,440 watts, and the load on a 20-amp line should exceed no more than 1,920 watts.
How can you know the load on a circuit? Add up the individual wattages for all lamps and appliances plugged into each circuit. When computing the load on each branch circuit, allow for motor-driven appliances that draw more current when the motor is just starting up than when it's running. A refrigerator, for example, might draw up to 15 amps initially but will quickly settle down to around 4 amps. Suppose the refrigerator is plugged into a 20-amp branch circuit and a 1,000-watt electric toaster (which draws a little more than 8 amps) is also plugged into that circuit. If the refrigerator motor starts while the toaster is toasting, the total current load will exceed the current-carrying capacity of the circuit, and the fuse will blow or the circuit breaker will trip.
Keep reading to learn about proper safety practices when you're working with your home electricity system.
Electrical Safety Tips
Some home electrical repairs require a licensed electrician, but the repair or replacement of many electrical components can be done by a do-it-yourselfer. Make safety your first priority, and you'll be amazed at what you can do to maintain and upgrade the electrical devices in your home.
All electrical devices and electrical wires are designed to provide the greatest measure of electrical safety, but you can defeat any built-in safeguards with carelessness and ignorance. To work safely with electricity, be aware of the following hazards and precautions:
Never do anything that would break the conductor's insulation. Do not, for example, staple an extension cord to a baseboard or wall. The staple can cut through the insulation and create a short circuit, which, in turn, can start a fire. Moreover, you should examine all wiring regularly and discard any cord with brittle insulation. Replace the old cord with a new one that has good insulation.
Turn the power off before replacing a receptacle or a switch or doing any other work on a circuit. If your system operates with fuses, remove the fuse for the circuit you're working on and slip it into your pocket or toolbox. If you leave it nearby, someone might put the fuse back in while you're working on the circuit. If your home's electrical system uses circuit breakers, trip the appropriate circuit breaker to its OFF position. Then, to make sure no one accidentally flips the circuit breaker back on while you're working, put a piece of tape and a sign over the circuit breaker's handle telling people what you're doing.
When you work on an electrical circuit, make all wire joints and connections inside an approved electrical box. There are several ways to join wires, but the best way is to use solderless connectors of either the crimp-on or screw-on wirenut kind. Never connect wires together in a behind-the-wall or in-the-ceiling location that is not accessible by simply opening an electrical box. In addition, when joining insulated wires to one another or when fastening them under terminal screws, make sure no uninsulated or bare wire extends beyond the connection. The insulation should go right up to the solderless connector or terminal screw.
Everyone in the family should know where and how to throw the master switch that cuts off all electrical current.
- If there's a chance of contact between water and electricity, do not wade in water until the master switch has been shut off.
- Always assume an electrical receptacle or apparatus is energized until you prove otherwise with a circuit tester or by pulling a fuse or tripping the disconnect plug.
- Use only insulated pliers when working with electricity.
- Stand on a dry board or wooden platform when working with a fuse box or circuit breaker box. Also, use a wooden rather than an aluminum stepladder to minimize the risk of shock when working with electrical wiring.
- You can save time by determining which electrical circuits activate which receptacles in your home and then diagramming or printing the information inside the circuit breaker or fuse box.
Proper grounding of your electrical system is essential to your safety. Electricity always follows the path of least resistance, and that path could be you whenever an appliance or another electrical component is not grounded.
Grounding directs electrical energy into the earth by providing a conductor that is less resistant than you are. This is accomplished by attaching one end of the wire to the frame of an appliance and fastening the other end to a coldwater pipe. Most plastic-coated electrical cable contains a bare wire, which carries the grounded connection to every electrical box, receptacle, and appliance in your home. You can usually tell whether your electrical system is grounded by checking the receptacles. If you have the kind that accepts plugs with two blades and one prong, your system should have three wires, one of which is a grounding wire. The prong carries the safety ground to the metal frame of any appliance that has a three-wire plug and cord.
An appliance"s metal frame can pose a safety hazard to you and your family. If a power cord"s insulation wears away just at the point where the cord enters the metal frame, contact between the metal current conductor and the metal frame could make the whole appliance alive with electricity. Touching a charged metal frame of the appliance while simultaneously touching a water faucet or a radiator will make the current surge through you.
There are other places throughout the electrical system where conductor/metal contact is a distinct possibility and a safety hazard. Be sure to inspect, maintain, and make repairs wherever wires enter a metal pipe (conduit), where the cord enters a lamp or lamp socket, and where in-wall cable enters an electrical box. Surfaces at these points must be free of burrs that could chafe the wire and damage its insulation. Washers and grommets protect the wire at these various points of entry. However, the best thing you can do to ensure a safe electrical system is to make sure the whole system is grounded and the ground circuit is electrically continuous, without any breaks.
The bottom line is that you need to make electrical safety a top priority whenever you do home repairs. Furthermore, don"t hesitate to call on a professional electrician when necessary.
On the next page, we"ll take a look at how to restore a circuit and what steps you should take in a power outage.
How to Restore a Circuit
The fuses or circuit breakers in your home electrical system are there for a purpose: to blow or trip if the circuit is overloaded. When that happens, as it does from time to time in almost every home, what do you do?
The first step should be taken even before a circuit trips. If you haven"t already done so, make a list of all the branch circuits in your home by number and by what area each one controls. Then you can figure out which receptacles and fixtures are on each branch circuit. If you aren"t sure the list is accurate and complete, you can verify it with a very simple procedure. Remove a fuse or trip a circuit breaker to its OFF position, then check to see what equipment or devices are deenergized. Of course, it"s easy to see when a ceiling light goes out, but you can check a receptacle just as easily by plugging in a lamp. A small night-light is an ideal indicator. Once you know exactly which receptacles, fixtures, and appliances are connected to each branch circuit, write all the information on a card, and attach the card inside the door of the main entrance panel.
When a circuit goes off, there may be some visual or audible indication of the trouble spot, such as a bright flare from a lamp or a sputtering, sparking sound from an appliance, that will immediately lead you to the source of the trouble. If so, disconnect the faulty equipment. Take a flashlight, and go to the main entrance panel. Check to see which fuse is blown or which breaker has tripped, and determine from your information card which receptacles, appliances, and lighting fixtures are on the circuit. Then disconnect everything on that circuit you can, and inspect those fixtures you can"t easily disconnect for signs (or smells) of malfunction.
Replace the fuse, or reset the breaker. If the circuit holds, it"s possible something you disconnected is faulty. Check for short circuits or other problems. If there"s no evidence of electrical fault in the fixtures, the problem may be too much current draw for the circuit to handle. In this case, remove some of the load from the circuit.
If the new fuse blows or the circuit breaker refuses to reset, the problem lies in either the equipment that"s still connected or in the circuit cable itself. Check the still-connected items, examining each for faults until you find the offending equipment. If the circuit still goes out when there are no loads connected to it, the wiring is faulty, probably due to a short in a junction or receptacle box or in the cable itself. If you suspect faulty electrical wiring, call an electrician.
A circuit breaker is a remarkably trouble-free device, but once in a while a breaker does fail. The result is the circuit will not energize, even when it"s fault-free. When a circuit goes out, if the circuit breaker itself has a distinctive burnt plastic smell, if the trip handle is loose and wobbly, or if the breaker rattles when you move it, the breaker has probably failed. Turn off the circuit, check the breaker with a continuity tester, and replace it as needed.
Coping With a Power Outage
What do you do when all the power in the house goes off? Usually this is due to a general power outage in an entire neighborhood or district, but sometimes the problem lies in an individual residential wiring system.
The first step is to see whether the outage is a general power outage or restricted to your home. If it"s nighttime, look around the neighborhood to see if everyone else"s lights are off. During the day, call a neighbor to see if others are affected. Or, if you have a circuit breaker main disconnect, check to see whether it has tripped to the OFF position. If the main entrance is wired with fuses, pull the fuse block out and slip the fuses free. Check them with a continuity tester to see if they are still good. With a probe lead touched to each end of the fuse, the tester light will come on if the fuse is good.
If the trouble is a general power outage, all you can do is call the power company. If your main breaker is still in the ON position or both main fuses are good but your neighbors have power and you don"t, the fault lies between your main entrance panel and the power transmission lines. The reason could be a downed service drop, a faulty or overloaded pole transformer, or some similar problem. Call the power company; this part of your system is their responsibility. If you find a tripped main breaker or blown main fuses in your main entrance panel, the problem lies within the house and may be serious. Do not attempt to reset the breaker or replace the fuses. The difficulty may be a system overload, using more total current than the main breaker can pass. Or there may be a dead short somewhere in the house.
The first step is to go back through the house and turn off everything you can. Then, if you have a circuit breaker panel, flip all the breakers to the OFF position. Once the breakers are off, reset the main breaker to the ON position. One by one, trip the branch circuit breakers back on. If one of them fails to reset, or if the main breaker trips off again as you trip the branch breaker on, the source of the trouble lies in that circuit. The circuit will have to be cleared of the fault.
If all the breakers go back on and the main breaker stays on, you"re faced with two possibilities. One is that something you disconnected earlier is faulty. Go back along the line, inspect each item for possible fault, and plug each one back in. Sooner or later you"ll discover which one is causing the problem, either visually or by noticing that a breaker trips off when you reconnect it. The other possibility is systemwide overloading.
This is characterized by recurrent tripping out of the main breaker when practically everything in the house is running but there are no electrical faults to be found. To solve this problem, you can either lessen the total electrical load or install a new larger main entrance panel with new branch circuits to serve areas of heavy electrical usage and help share the total load. This job requires a licensed electrician.
The troubleshooting approach is similar if the main panel has fuses, except you"ll need a supply of fuses on hand. First, pull all the cartridge fuses and unscrew all the plug fuses in the panel. Replace the main fuses, and put the fuse block back into place. Then, one by one, replace each fuse or set of fuses until the one that"s causing the outage blows out again. This is the circuit that must be cleared. General overloading, however, will cause the main fuses to go out again. If this happens, call in an electrician, who can test for overloading and suggest remedies.
Assembling an Emergency Blackout Kit
Is your home susceptible to power outages due to the local utility company, wind storms, or other problems? Even if it"s not, you would be well served to make an emergency blackout kit that includes the following items:
©2006 Publications International, Ltd.
Some items for a blackout kit.
Candles or oil lamps and matches for area lighting
- Flashlight, battery lantern, or other auxiliary light source for troubleshooting
- Correct and up-to-date circuit directory posted on main entrance panel door
- Tool kit with appropriate tools for making electrical repairs
- Circuit tester, preferably the voltage-readout type
- Two replacement plug fuses of each amperage rating in use, preferably Type S
- Four replacement cartridge fuses, including main fuses, of each amperage rating in use
- One replacement pull circuit breaker of a rating equal to the smallest size in use or one of each size in use
- One replacement double-pull circuit breaker of each amperage rating in use
- Selection of lightbulbs
- One replacement duplex receptacle to match existing units
- One replacement single-pole switch to match existing units
- One replacement three-way or other special switches to match existing units
- Wirenuts and electrical tape
With a little preparation and knowledge, you"ll be able to handle your next power outage without being left in the dark.
It also takes preparation and knowledge to do repairs and maintenance checks on home electrical receptacles. We"ll show you how to perform these tasks in the next section.
How to Restore a Circuit
Residential wiring systems installed in older homes use a two-wire system in the 110-120-volt branch circuits. One conductor is hot, and the other is neutral. The neutral may also serve as a ground, but, unfortunately, it usually does not. When this is the case, the system is ungrounded and the situation is potentially hazardous.
You can easily tell if your circuits are of this type by looking at receptacles. There are only two slots for each plug in ungrounded receptacles. Modern wiring calls for the installation of a third conductor. Receptacles used with this system have three openings: two vertical slots and a third, rounded hole centered below or above them.
©2006 Publications International, Ltd.
A plug-in polarity checker can enable
you to make sure your outlets
are installed properly.
Either two-prong or three-prong plugs can be plugged into these receptacles, but only the three-prong kind will carry the equipment grounding line to the electrical equipment. Also, one of the vertical slots is different in size from the other, so the newer types of two-pronged plugs can be inserted in only one direction. This ensures that the equipment being connected will be properly polarized, hot side to hot side and neutral to neutral.
For proper operation and safety, make sure all receptacles on each circuit are installed with the individual conductors going to the correct terminals so there are no polarity reversals along the line. Unfortunately, receptacles are not always connected this way, even in new wiring systems installed by professional electricians. Check out your receptacles with a small inexpensive tester called a polarity checker, designed for this purpose. It looks like a fancy three-pronged plug and contains three neon bulb indicators.
To check your receptacles for polarity, plug a polarity checker into a receptacle. The lights will tell you if the polarity is correct and, if not, which lines are reversed. If there is a reversal, turn the circuit off, pull the receptacle out of the electrical box, and switch the wires to the proper terminals. If the equipment-grounding circuit is open (discontinuous), trace the circuit with a continuity tester until you find the disconnection or missing link; reconnect it to restore the effectiveness of the circuit.
Replacing an Electrical Receptacle
What You"ll Need
Here are the tools you"ll want to have when replacing an electrical receptacle:
Nearly everyone has come across an electrical receptacle that doesn"t work as well as it should or one that doesn"t work at all. How does it happen that a receptacle fails to do its job efficiently and safely? There are two possible explanations.
An electrical receptacle can be permanently damaged through improper use. Sticking a hairpin or a paper clip in it, for example, can shorten a receptacle"s -- and your -- life.
You may never do anything as foolish as sticking a paper clip in an electrical receptacle, but you can do the same damage when you plug in an appliance with a short circuit. Regardless of how the damage occurred, the damaged electrical receptacle must be replaced.
Another possible explanation for an electrical receptacle that doesn"t work efficiently and safely is that it is just so old and has been used so often that it"s worn out.
There are two clear indications of a worn-out electrical receptacle: the cord"s weight pulls the plug out of the receptacle or the plug blades do not make constant electrical contact within the receptacle slots. At that point, the old electrical receptacle should be replaced.
This is not difficult, but you must follow the correct installation procedures precisely. Here"s what you should do:
Step 1: Before working on electrical receptacle, deenergize circuit that controls it. Inspect old receptacle to see whether it can take a plug with a round prong (for grounding) in addition to two flat blades. Buy new receptacle with 20-amp rating of same type -- grounded or ungrounded -- as one you"re replacing.
Step 2: Take off plate that covers receptacle by removing center screw with screwdriver. If cover doesn"t come off easily, it"s probably being held in place by several coats of paint. Carefully cut paint closely around edge of cover plate with razor blade or utility knife.
Step 3: Remove two screws holding receptacle in electrical box. Carefully pull receptacle out of box as far as attached line wires allow. Loosen terminal screws on receptacle and remove line wires. Caution: If wires or insulation is brittle or frayed, that part of circuit should be professionally rewired.
Step 5: Carefully fold wires into space in electrical box behind receptacle, then push receptacle into box. Although there"s no such thing as right side up for a two-blade receptacle, there is a correct position for receptacles designed to handle three-prong grounding plugs. Grounding plugs often attach to their cords at a right angle, so you should position receptacle so cord will hang down without a loop.
Step 6: Tighten the two screws that hold receptacle in receptacle box, then replace cover plate. Restore fuse or trip circuit breaker.
Slots in some electrical receptacles are not identical; one is wider than the other. The wider one connects to the white or neutral wire, while the narrower slot connects to the black or hot wire. Some plugs, in fact, are designed with one wide and one narrow blade, and these plugs will fit into the receptacle in only one way. The idea behind such a polarized plug is to continue the hot and neutral wire identity from the circuit to the appliance.