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Does a circuit breaker go bad or get weak?
It doesn't start tripping at a lower level than it should, unless a loose connection/contact in/under/at it is making heat that throws it off. There are cases where the handle of the breaker mechanically will not reset, but it is more common that failure to reset is from a short that is retripping it immediately or is from the person not knowing the right procedure for resetting. Of all home wiring problems, breakers get a lot of suspicion, and only a fraction of it is deserved.
How can I tell if a circuit breaker is bad?
(In general see Test). You can replace it or move its wire temporarily to another breaker. If this doesn't improve things, the old breaker is fine; look for another cause than the breaker. For instance, an Open.
What is a GFI for?
A GFI receptacle or a GFI breaker is to prevent fatal shocks at likely locations -- where people operating faulty tools or appliances can easily become a good path to ground, completing an unintended circuit.
Is there a difference between a GFI and a GFCI?
GFI stands for "ground-fault interrupter". GFCI stands for "ground-fault circuit interrupter". They are the same thing. I prefer "GFI" because the word "circuit" is ambiguous or superfluous in most contexts.
What does the little light on a GFCI outlet mean?
Many newer GFCIs do have an LED light, but they mean different things on different brands. So I have not tried to memorize the light colors and their meanings. But if a GFCI normally shows no light but does now, or if it normally shows a light and now doesn't, then this is probably to tell you that the GFCI is tripped. In addition, the presence of a lit light also tells you that the GFCI has power available to it, so that its inability to run things is from being tripped and not from lacking power to its box.
How does a GFI work?
By "work" here you mean how does it know to trip off. (A GFI receptacle/outlet also "works" as any outlet does: by running what you plug into it). A GFI trips off (stopping power at itself and at any normal outlets wired downstream from it) by comparing how much current is flowing on its hot versus its neutral wires; it trips if these are different by a small fraction of one amp, which would be the result of someone being shocked (giving current an alternate path than just between hot and neutral). But, unfortunately, many other conditions are able to trip these devices than someone being shocked.
Why won't my GFI reset?
There are several possibilities. It may be responding to a ground-fault happening somewhere downstream (at regular outlets that are now dead, for instance). It could be the GFI itself has no power reaching its electrical box because of a short or an open or another GFI that is tripped upstream from it. Tripped GFIs made since 2002 will not let you reset them if power is not getting to their line terminals. See GFIs.
Does a GFI go bad, and how can I tell?
The main way a GFI truly goes bad is that it still runs things after you push the test button. In that case, it is not protecting anyone from fatal shock, at itself or at other outlets it was protecting. The idea that a GFI might be bad because it won't reset is almost always wrong. GFIs made since 2002 won't reset if they are not receiving good power in the first place. And a GFI made before 2002, whose reset stays in, can fail to run things for the same reason -- not receiving good power itself. In other cases a GFI "not resetting" is just retripping, for some kind of ground-fault; this is not a case of the "GFI going bad" either; it calls for correcting a fault condition downstream from the GFI. Only once or twice have I seen a GFI trip or fail to reset from a mechanical problem in it. See GFIs.
If my GFI (GFCI) won't reset, should I replace it?
You could, but it is much more common for a GFI receptacle to retrip (or to not reset) for other reasons than a bad GFI. Your new GFCI would probably not reset either. I wouldn't suspect the GFI itself till I had ruled out the more usual causes. Here they are. There could be a ground-fault happening at some "downstream" wire or receptacle or item plugged in. Your GFI that won't reset could have been installed incorrectly recently; since 2002 GFI receptacles have had a feature that won't let them reset if they are hooked up wrong or if power is not on. Learn more about GFIs.
Why are switches called 3-way when there are only two switches?
Only because there are three terminals on the switch mechanism, which isn't a good reason in my opinion. It is true, however, that the switches used to switch lights from multiple locations are not all the same type of switch. Two of them have the three terminals, but any additional locations beyond the two have to use switches with four terminals, called 4-way. To be even more technical, a 3-way switch is a single-pole double-throw switch, and a 4-way switch is a double-pole double throw switch arranged for pole-reversing. See 3- and 4-way info.
We replaced some switches and now the new ones don't work quite right. Why?
You probably hooked the new ones up incorrectly. If the switches involved were 3- or 4- way type, the new switches may have a different arrangement of terminals than the old ones did. If the switches involved were normal on-off (single pole) type and there were more than two wires to attach, you may have attached a wrong wire somewhere or you may have failed to attach one at all, since the switch only seemed to call for two. See Pitfalls of upgrading.
I lost track of how the wires were connected to the old switch. How can I know what to do without trying dozens of possibilities?
For this you need to learn more about how switches work or more about how wires in an electrical box are able to use the switch terminals to achieve switching or to achieve a passing of unswitched hotness on to more of the circuit. See my Tour of a circuit or Correcting connections.
Can you help me hook up a 4-way switch right?
Yes, I can at least advise you so your choices and experimentation are minimized. Two of the switch's terminal screws are one color (brassy?) and the other two another color (dark?). Of all the wires in the switch box, two that come from one cable as it enters the box will attach to the two screws of one color, and two wires that come from the other cable (I hope there are just two cables total) will attach to the screws of the other color. If there are more than two wires in both of those cables, the third wires of each cable would attach to each other, not to the switch [hopefully these "third' wires were identified by already being joined, so that you don't have to experiment to find out which of the three wires in a cable is this "third" one]. Colors can vary. See 3- and 4-way info.
What is electricity?
Well, tame electricity (not static electricity or lightning) is essentially a force generated onto loops of conductive material, transferred through their electrons, and applied as useful energy at parts of these loops.
What is meant by a circuit?
A circuit is the actual or intended path of current between points of differing voltage. In the case of a household 120 volt circuit, the path is through a "hot" wire from the breaker, an item that is using the electricity, and a "neutral" wire connected to the grounded neutral bar in the panel. In a sense each loop that current makes (through a single light and its switch, for instance) is a circuit but the most common meaning is the "branch circuit", that is, everything fed (or interrupted) by a given breaker or fuse. See Your electrical system.
To avoid getting shocked if I work on my system, do I need to turn off all power to the home?
It's not a bad idea. If you know enough about your system to turn less off at once, you may be safe turning a single breaker off or just a GFI or switch. It is also a good habit to treat all wires as live anyway, even when you have checked and know they are dead. You don't know everything, and you don't have control of other people in the home who might forget about you and turn something back on. See Safety.
Which wires are supposed to attach where on a receptacle (outlet)?
As you look at the face of the receptacle with its slots above its hole, the (shorter) slot on the right gets the hot (black/red) wire(s) by attachment on that side. The longer slot on the left gets the neutral (white) wire(s) by attachment on that side. The hole gets the (bare/green) ground wire by attachment to the green screw. See Connections and Connections tutorial.
Which wires of a light fixture are supposed to connect to the black, the white, and the bare (or green or when no-such exists) wire at the light box?
If there is a bare or green wire in the box, attach the fixture's bare or green (if any) to it, otherwise leave the fixture's alone. If the other wires of the fixture are black and white, connect them each to the same color wire in the box (but if a single red is waiting in the box, attaching the fixture's black to it and not to the blacks in the box is probably the right move). If the fixture's two non-ground wires are not black and white but one of them is smooth and the other has a "ribbed" texture, the ribbed is to connect to the white of the box and the smooth to the other. But if the fixture's wires fit none of these descriptions, one of the two should be a solid color (it connects to the hot; except if it is solid white, connect it to the white) and the other should have striping or lettering on it (it goes to the white neutral; except if its mate was solid white, this striped one goes to the black or red). Is everything clear?
Can you help me understand how a circuit in my home operates?
For this I refer you to my Background material and also to my Tour of a Circuit [or frames version].
Is there a way to map out the circuits in my home?
A thorough mapping would mean you know what box every part of the circuit branches out from. But maybe you just need to know all the things running off each separate circuit breaker. It can take some work. I have a page on how to go about Labeling your panel.
What goes wrong with circuits?
You can lose power or part of your power. Your automatic breakers or GFCIs can switch things off. Your lights can flicker or get bright or strangely dim. To understand why such things happen, see this Background material.
How can I turn off all my power so I can be safe checking or working on my wiring?
There may be a single main shut-off breaker in your main panelbox or somewhere close by, indoors or outside. Or it may be you will need to turn off as many as six different breakers or levers. If unsure, turning off all breakers and pulling out all fuses you are aware of -- indoors and out -- should work, but a tester that will confirm voltage is gone will make you sure. See Testers.
What is meant by pigtailing?
Pigtailing is combining two or more wires with an additional wire which will be the one to attach to a terminal. Screw terminals that clamp down on wires you insert in nearby holes often let you connect more than one wire there, so that there is no need to pigtail. But more often the screws only take wires curled clockwise directly under themselves; then only one wire should be put under each screw, and so it may be necessary to pigtail so that all the (say, white) wires of the circuit connecting there have contact with each other. On some devices there are (additional) holes for terminating wires by simply pushing wires in till they catch. If there are enough such holes, pigtailing will not be needed. Such holes on receptacles will not accept large (12 gauge) wires, in which case the wires will need to be pigtailed if there are not enough screws to put them all under. An example of pigtailing diagrammed.
Can I tell if my home is wired safely?
Honestly, no. Not even an inspector or electrician can. Some things are hidden from view and from testing. An investigation that tried to be as thorough as possible would still fall short. Even when something loose or against Code is discovered, the degree of hazard it presents is disputable. Most "potentially unsafe" conditions will show themselves as outages, flickerings, shorts, or shocks; and when they do, most prove themselves to be minor or contained. I am not saying an inspection and someone's opinion of the results are pointless or of no value. But because people (even "sincere" people) can make money off your anxieties, the truth about your risk and about their thoroughness can get exaggerated. See my Safety opinions.
What is the difference between hot, neutral, and ground wires?
When connected properly, these wires serve different functions, as follows. Hot ("live") wires provide a circuit's path between the breaker and any lights or appliances. Neutral wires provide the rest of the path, that is, the path between these same lights or appliances and the panel's grounded neutral bar. The ground wires, like neutrals, are connected to the grounding point in the panel, but they are not supposed to carry current under normal conditions. In an abnormal condition like the hot shorting to metal parts nearby, the ground wire is meant (by its attachment to such metal) to carry a great amount of current suddenly, so as to trip the hot's breaker and stop the condition. More.
What is the difference between open, overload, short, ground-fault?
An open is when a circuit's path is disrupted. An overload is when current on a circuit is a bit excessive. A short is when current takes an unintended path to ground (usually with very little resistance). A ground-fault is when such a short does not use the neutral as its path to ground. More.
What does open ground mean? open neutral? reverse polarity, etc.?
Measured at an outlet's receptacle, the path (wire continuity) to the ground point in the panel can be disrupted or missing for the ground wire (open ground) or for the neutral (open neutral). When it is the path between the outlet and its circuit breaker that is disrupted, this is called an open hot. Reverse polarity (hot and neutral reversed) means neutral wires are connected to the side of the receptacle that is supposed to be for the hots, and vice versa. See Testing and Outlet corrections.
What is the difference between Line and Load?
For this, see the Glossary.
What is the difference between current, voltage, resistance, and wattage?
Voltage pushes current through a resistance, using power (wattage). More at Glossary.
What is the difference between amperes, ohms, watts, and volts?
W volts push X amperes through Y ohms, using Z watts. Amps times ohms = volts. Amps times volts = watts. See Glossary.
What is the difference between outlet, receptacle, plug, switch, breaker?
A switch makes or breaks continuity. A breaker is a switch that automatically breaks continuity when current is too high. An outlet is technically where a light or appliance gets its connection to the circuit's wires. A receptacle is the device we often call "outlet" for plugging cords into. More at Glossary.
What is the difference between fixture, device, appliance?
A fixture is a non-portable light. An appliance is anything else than a light that uses (up) wattage. A device (e.g., switch, breaker, receptacle) is for passing or purposely disrupting the continuity of the circuit to fixtures, appliances, or lamps. See Glossary.
Why do some circuits seem to go all over the place without obvious reason?
There are many Code provisions saying where some circuits may not extend, where they must be provided; where switches, fixtures, and receptacles must and may not be. But residential Code and blueprints do not say everything about how circuits should run. Within code, electricians will then choose convenient and material-saving routes for their cables.
How many things can be on a circuit; how many wired off a GFI?
For a general purpose circuit, the limitation is mainly this: a 15-amp circuit should not extend over more than 600 sq.ft. of the home; a 20-amp circuit not over 800 sq.ft. Some GFI manufacturers only stand behind their device's ability to help eight outlets downstream, but this is arbitrary. It is reported that a very lengthy set of GFI loads can set up enough capacitance to trip the GFI. If that is suspected, each such load outlet could be given its own GFI receptacle, connected to protect only itself.
When were different things required by code?
That's a large question. For GFI requirements and for kitchen and bathroom circuit requirements, see GFI locations. For arc-fault interrupters, see AFCIs.
How can a circuit go out with no breaker or GFCI tripped?
In a word, by a connection being bad somewhere. The whole circuit would fail to work if a connection-point at the breaker or at the circuit's neutral in the panel became loose or deteriorated. More often these "opens" involve less than the entire circuit because a connection out on the circuit -- at an outlet box for instance -- has failed.
Some things are not working; how can I know where to look for the problem?
If you have checked bulbs and generator switches, and have reset any breakers and GFIs, you will probably need to look for an open (loose, corroded, broken) connection. Learn about Troubleshooting outages.
Some things will go out for awhile and later come back on (on their own); what is that?
That is a poor connection being poorer sometimes and better at other times. It may be generating some heat at the poor spot whenever it does run things. It will tend to progress toward staying out and never coming back on. See Comes and goes.
Why would a neutral wire read live?
When a neutral is not continuous back to the panel like it should be, the hotness of the hot wire still goes through anything that is ready to run (but won't) and shows up on the normally-neutral wire.
I've narrowed my outage down to a loose hot or neutral somewhere; can I find the spot without tearing everything apart?
Maybe. For details on how to narrow the spot down see Finding your open.
I've checked, tightened, or replaced all my dead outlets and switches, and they're still dead. Now what?
Have you considered that the bad connection can be at a nearby working outlet or switch as easily as at a dead one? There may be odd places you haven't checked -- another room (downstairs?), a smoke alarm box or a doorbell transformer box (in a closet).
How can I tell if I am overloading a circuit?
Most easily by letting the breaker trip and then recall what all was running that now is dead. If the breaker doesn't trip, you are not overloading. Are you "overloading" a receptacle, surge strip, or extension cord by the number of things you have plugged in? Not likely, although you should check the tag on the extension cord for the most watts you should have running on it. Even when these things are within their limits, any cord or receptacle can get hotter than it should because of a defect in or damage to it; if you notice extreme heat, replacement is a good idea.
The breaker often trips when I am using the vacuum (or hairdryer or iron); is that normal and what can I do?
It is almost normal, since the manufacturers of vacuums and hairdryers have increased the percentage of a circuit's capacity their appliances use. If it is too inconvenient to live with this problem, a new circuit to an outlet just for such a heavy user will do the trick.
Do you have a diagram of how switches or outlets are usually hooked up?
Yes, several. For instance, see my Tour of a circuit, or Connections tutorial.
Do you have a diagram of how cables are usually run in a home?
Yes, it is called Floorplan. There are common methods of wiring a house or apartment, but not quite a "usual" way.
Do you have a diagram of a main electrical panel box or how a 240-volt circuit is hooked up?
Yes, you'll see a few of these in Your Electrical System.
I get shocked when touching two things at once but not either alone; which one is bad?
Without a tester, the only way to tell is to touch a third or fourth thing from each, at some risk to your health! So I recommend a neon tester or a non-contact tester. See Testers and Shock.
We get shocked off faucets or pipes sometimes; what can we do?
If you live close to some big or tall or main lines of your power company, those lines may be creating voltage on your pipes; the power company may or may not be able to help. Otherwise, the particular circuit responsible can be identified and the stray wire located. See Shock. Plus the grounding of those pipes should be checked and insured.
Will it be easy for me to replace switches and outlets in my home?
Physically, maybe. Electrically, no. For most people, the unknowns they will encounter when they get into this simple sounding project will begin to baffle them. If they go forward anyway, they are likely to end up with one or more malfunctions when they turn power back on and try using things. If they are lucky and everything seems to check out fine, their inexperience at making the new connections may still result in problems in the future. Learn the Pitfalls of upgrading.
I replaced several receptacles or switches with new ones; things don't work quite right now; what did I do?
You'll need to go back over the work you did before you noticed, and see if all connections are solid, none missing, and whether perhaps something was connected to the wrong place. See Pitfalls of upgrading.
I am replacing old switches or outlets but have maybe lost track of how they were connected; is there a standard way or diagram?
Without consulting me or another electrician, your best bet is the examples in my Tour of a Circuit or the Connections diagram.
What is the green screw on my new switch for?
Because people have been replacing plastic switch covers with decorative metal ones, code has now required the switches to be grounded, so that the covers attached to them will never be able to shock if a hot wire or terminal were to get loose and touch either. So to put the new switch in right, you'll dig the bundle of ground wires out from the back of the box and pigtail a wire from them to this green screw.
Where is the flickering of my lights coming from?
From a poor connection or contact somewhere along the circuit or even at a main wire outdoors or in the panel. Finding the problem-point isn't usually easy. See Flicker.
My lights dim down for a time or get extra bright; what's going on?
Some dimming when a copier, iron, or motor comes on is normal. Otherwise, a neutral wire -- usually the main one at the panel or outside from the power company -- could be having trouble. This would be confirmed if you also notice unusual brightening of other lights or of the same lights at other times. Repair is more likely to be a job for the power company than for an electrician or yourself. See Main open and Two Circuit.
I turn an appliance on and it makes lights that were dead come on; what's happening?
A main hot wire is having trouble at the panel or outside. The power company is often responsible, so call them first. Otherwise or later, an electrician. To understand what is going on see Weird electrical.
Why is my light, switch, or breaker box humming?
Many dimmer switches will set up a hum at the light bulbs. At the breaker panel, the 60 cycles per second of your alternating current is able to set up a vibration or slight buzz or hum in some components there. Fluorescent lights, transformers, and an electric water heater can be heard humming also. All these are fairly normal, but if a hum is quite loud, it may mean a component is loose or close to failing. I have come across wet circuit breakers buzzing as they boil their water and a case where a loud hum was a breaker carrying a significant overload without tripping as it should have.
Why does my breaker hum or spark and then turn off?
If it makes this noise as soon as it is turned on and then trips off quickly or within ten seconds, there is a short circuit occurring somewhere out on the circuit. See Short. If sparking or "fizzling" is heard or seen but the breaker doesn't go off till a minute or more has elapsed, the breaker itself is probably having a connection problem and will probably need to be replaced, with the new one put in a different position in the panel if possible.
Should I be concerned that a certain switch or outlet gets hot?
An outlet getting hot means that wires connecting to it are loose and need help or that the outlet needs to be replaced because its receivers that a cord plugs into are weak. I would be concerned to take care of either of these scenarios. A hot switch is usually a dimmer switch (it may or may not still be able to dim lights). If the dimmer is trying to dim more than 600 watts worth of light bulbs, it is probably overloaded. In that case install one rated to handle more watts or replace bulbs with lower-watt ones.
Why is a circuit breaker so hot?
Breakers will be mildly warm when running things, but if one is hotter (not necessarily too hot to touch) it might be having trouble with a poor connection at or in it. Consider what it is running. If a heavy load (a space heater, for instance) has been running for perhaps a solid hour, this would be normal, even though the breaker might be about to trip from the heat.
I've smelled something funny like hot plastic; what might be happening?
It isn't always easy to pinpoint where smells are coming from, but try. It might not be from an electrical source, but it might be. Sniff up close to outlets and switches when you notice the smell. Ask your dog to help you; seriously. If the smell is from something electrical, it will be from a poor connection that is creating heat, melting or charring plastic components. This presents a possible fire hazard.
Why do the bulbs of a certain fixture burn out a lot?
When a fixture cannot dissipate the heat of its bulbs, it takes a toll on the bulbs and on the fixture's sockets and wires. If the lights are ones that are left on a lot -- like outdoor lights left on all night -- then the bulbs may be living their full life but will simply have to be changed more often than others. But other things can contribute to early failure. Bulbs may be of cheap quality. Or there may be loose arcing connections at the socket or in connections to the light.
Why do many bulbs around the house burn out sooner than they should?
There are various reasons that bulbs will burn out too soon. Bulbs may be of cheap quality. Or there may be loose arcing connections in the wiring of a circuit. The life expectancy of a bulb will also be affected by the quality of power from the power company. This includes the little surges and spikes that are better known for their effect on computers. But it also includes the basic voltage level coming to the home from the utility. Many homes receive more than the average 120 volts that most bulbs are designed to handle and this shortens their stated life. A good solution to this is to look for the same bulb but with a "130v" rating stamped on the bulb instead of "120v". The light output of these won’t be quite as bright, but you will spend less of your time getting the ladder or stool out again.
Several bulbs (got real bright and) burned out about the same time.
You may have a loose neutral that is shared by two circuits and that sometimes allows high voltage to hit one of the circuits. See Two circuit. Or a poor neutral could be the main neutral. See Main open. Or none of the above (often hard to know what was responsible, after the fact).
To be safe, should I have my whole electrical system checked out, and how often?
Without any definite specific symptoms, there is no reason to have things checked more than once, if that, during your tenure at a home. Unless you enjoy being paranoid. And don't let anyone confuse you between technical code violations and active hazards.
How likely is an electrical fire?
That's a slippery question. You can see my thoughts on this in Opinions.
What is the right tester to use for my problem?
See Testing.
What does this 3-prong outlet tester mean by an open ground, open neutral, reverse polarity, or "hot and ground reversed"?
See Outlet corrections.
How would I test for a good or bad neutral, hot, or ground?
The best all-around is a neon tester. With one probe in the palm or your hand and the other to a possible hot, it glows for a hot. With one probe to the hot, it glows even brighter when the other is to a good neutral or ground. For exceptions, see Testing.
How would I test for a good or bad switch, receptacle, GFCI, breaker, or fuse? (Also see Testing).
If a hooked up non-dimmer non-3way switch shows hot at one terminal (neon tester in hand) but not at the other when the switch is turned to ON, the switch is bad. Or just join the switch's two wires; if the light works but didn't for the switch, the switch is bad. A receptacle may need replacing but that will be from not holding plugs well, or from it having overheated from a poor wire connection, or from being simply broken. These things need looking for; there is no other way of testing for "badness". If a GFI that can run things won't trip off for the test button, replace it. And if a GFI with good hot and neutral at its line terminals won't reset and run things when no load wires are connected, replace it (I have seen this only once or twice). Other than these, the GFI itself is good. A breaker's screw showing hot for your neon tester is good 95% of the time. If moving a breaker's wire to another breaker changes nothing in the circuit's behavior, the breaker was fine. A screwed-in fuse lighting a one-probe-in-hand neon tester touched to its outer threads is good; if it doesn't light, the fuse is bad IF it lights on the fuseholder's center when the fuse is removed. A cartridge fuse that can be probed while in place is good if one end is hot and neon probes to both ends gives no light; if one or both ends are hot but probes to both ends gives light, it is bad. If fuses must be pulled out to test, an ohmmeter showing 0-5 ohms means good, otherwise bad.
At not-working outlets I find full voltage between hot and ground but not hot to neutral. Why?
The neutral is open somewhere (poorly connected). See Outlet corrections.
The white neutrals at some dead items of my circuit register some voltage to ground. Why?
Something among the not-working items of the circuit is turned on, allowing hotness from the good hot wire to go through the lightbulb filament, say, and show up as somewhat hot where you are testing the white wires (which are usually neutral [grounded] but not now). See Testing.
I get a reading on my voltmeter or ohmmeter that I don't understand. Am I testing the right things?
Maybe not. There are a lot more readings hard to explain than those that make sense and tell you what you need to know. I don't test anything but what I know will probably give me usable information. When I don't understand a reading, I don't let it distract me; I think of a different way to test out what I need to know. Of course, knowing what and where to test is important and is worth some thought. See Testing.
My non-contact volt "stick" says something is live or dead, but other testers disagree. What's up?
A non-contact voltage-presence indicator is rated to say when a certain level (or greater) of AC voltage is present. In practice I have found that that level is elastic. Lower voltages can set it off at times, especially when placing the stick very close to a wire. Also voltage induced onto a wire from nearby wires can register. So it is often helpful to confirm what a stick says using other testers and to give the others higher credibility. See my Chart of testers. Live underground cables that are still close to the earth may not register liveness for a stick.
A breaker retrips when I reset it. If it is a short, where should I look?
If it is truly retripping, not having a rare mechanical problem, and you are attempting the reset correctly, then it is a short. On that circuit unplug everything and turn all simple switches off, and one end of any three-way switches the other way. If the short recurs upon resetting, see next question.
To find my short I turned off all the switches and unplugged everything of the circuit. Why is it still shorting?
The short is in a more permanent part of the wiring (in a box, receptacle, or wire). See Short. Have you made sure you know the extent of the circuit (outdoors, closets, attic, crawl space)?
I suspect that recent screws or nails hit a wire. Can I tell which screw?
If you are able (at the panel, for instance) to unconnect the neutral and ground wires and keep them isolated from anything grounded, then when the breaker is reset, it may not trip. If it does not trip, your ground and/or neutral wires will probably register hot, as will the theorized nail or screw and many appliances on the circuit! So put people out of the house before doing this! A non-contact voltage tester would then indicate pretty well which of all the screws is live. If you can touch its head with a neon tester (in hand), it will confirm the culprit. Extracting it might leave the cable functional and safe, but you could bare the structure to be sure or to make a definite repair.
Since my GFI keeps tripping, where do I look for the ground-fault?
This will be similar to finding a short circuit (above) with the additional aspect that the fault to ground can come from the hot or from the neutral. See Ground-fault.
How can I find what is tripping the GFI if it only happens once in awhile?
On this question, I share your pain. I haven't done it much, but theoretically an ohmmeter might show a non-infinite resistance of over 30k ohms between ground and either hot or neutral, when you test (with power off) at the downstream (load) side or at any fully disconnected point downstream. This resistance won't have been enough to trip the GFCI but may be enough to track down the fault. Unfortunately we can sometimes get a similar reading across wires that are virtually separate. Also this idea won't help much if the fault is to the earth alone, not to the ground wire.
How can I tell if a short, ground-fault, or open outdoors is in the earth or at a fixture/outlet?
If you can get access to all connection points of this line, you can unconnect just fixtures and outlets from the line and see if the fault remains when you try to reset. Otherwise, unconnecting where you can will let you narrow the possibilities down in a divide-and-conquer fashion. See Short and Ground-fault. An Open in the yard is a little likelier to be at a connection above ground, where it doesn't end up shorting so easily.
Am I allowed to make a splice in the breaker panel?
Yes. It would have to be 75% full of wires for the answer to be No.
Why would a new breaker go bad after awhile, like the old one did?
Because the way the old one went bad was by bad contact with the busbar, so that arcing there damaged the busbar. Put another new breaker in, but in a better place.
What is the best way to connect wires at a receptacle?
By pigtailing, if you do a good job of it. Second choice: wires wrapped clockwise under side-screws. Third choice: use a receptacle whose side-screws clamp the wires tight in holes. Last choice (and only for 14 gauge wire): the "quick wire" push-in holes on the back of the receptacle; this actually does OK most of the time and is the most common.
Why has my electric power bill been so high lately?
First, think of whether you have been using more; refer to Michael Bluejay's page on electric usage. You might also see if the power company is willing to check or replace their meter. If your water is heated electrically, a leaking hot water pipe would definitely explain a high bill. Beyond that, I know of one instance in which a ground-fault to the metal frame of a building ran up the bill; the condition usually did not trip a breaker because the building frame was not grounded and the current leaking into the earth remained mostly less than the 20-amp setting of the breaker.
