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This guide is mostly about commercial troubleshooting and repair, but we include this section on residential wiring in order to provide perspective. For the electrician, residential wiring is usually the gateway into the field. Most technical-oriented people are familiar with the infrastructures of their own homes, where they do routine repairs and maintenance as needed, including working on heat systems, air-conditioning, garage door openers, etc. An apprentice or beginning electrician is likely to work for an electrical contractor who specializes in residential work. Beginners are given menial but important tasks like moving materials and cleaning, and those with aptitude and ambition quickly graduate to actual electrical work.
Residential electrical installation differs markedly from commercial and industrial work.
Often it involves new construction on a large scale, as when extensive subdivisions are built. Every house may be essentially the same electrically, differing only in the location of the service due to differences in lot orientation. Much of the work involves repetitive tasks like drilling holes in studs and running wire between outlets. Speed and efficiency are of the essence, and supervisory personnel will urge the workers on to ever-higher levels of productivity. The commercial or industrial maintenance electrician, in contrast, must have a greater amount of knowledge and expertise to design, install, repair, and maintain the vast amount of equipment in use, but strangely the pay is often lower, and the work pace a little slower and more deliberate.
In residential work, the somewhat more complex work of alarm, communication, and data wiring is often but not always done by specialized subcontractors, so that the construction electrician is left with the simpler, but no less exacting, tasks of service and branch-circuit design and installation, and putting in light fixtures and fixed appliances.
In residential wiring, there are enormous moral and legal concerns. Safety for coworkers and end users must always be before the electrician. Think of the young child sleeping in a third-floor bedroom of a building you have wired.
To mount a fluorescent strip fixture on a sheet-rocked ceiling, it is necessary to screw through the drywall into framing. Do not worry if the holes in the fixture do not coincide. Use your cordless to screw right through the sheet metal without regard to the predrilled holes.
It is this precise issue that National Electrical Code (NEC) addresses. Protection from fire and electrical shock is the focus of the thousands of statements and table entries that comprise this work. It is fundamental to all electrical construction, and has great importance in the residential setting.
Like any wiring, having an informed approach begins with the design. The first step in residential work is to size out the electrical installation, based of course on the size of the house and its anticipated usage. The complete procedure for this process is found in NEC Section 2. The electrical load depends upon the number of square feet of the house, to which is added the load of each appliance, with exceptions and permitted derating factors. For example, only the larger of two loads that are not likely to be run concurrently must be included in the calculation of service and feeder conductor sizes. The classic example of this is heating and air-conditioning.
However, since our main interest is troubleshooting and repair, we will not undertake a close study of this important topic.
Problem Solving
It is a frequent occurrence for the electrician to be called in at some point after the new owners have taken possession of the premises, even decades later for older houses, to fix problems that have surfaced. Often the homeowner has attempted to do the work, but has been unable to carry it to completion. The same troubleshooting techniques are applicable in residential wiring systems as in electrically driven heavy machinery.
First, interview the owner/occupant. Find out whether the problem in the wiring always existed, suddenly appeared, or gradually emerged. If it existed right from the start, it probably resulted from a fault in the installation that was not serious enough to be noticed right away. An example of this is the battery-operated smoke alarm with backup ac that was initially bugged off the power supply to a light fixture, so that the ac mode works only when the switch is turned on.
If the problem emerged gradually, for example flickering lights, at first barely perceptible but eventually quite prominent, then the fault is time-dependent, and it is likely the result of a gradual increase in impedance at a single point in the wiring. This may be the result of corrosion, and it is a simple matter to clean or remake the connection, but the difficulty is often locating that point. (Each of these faults will be discussed shortly.) A whole other category involves ground-fault circuit-interrupter nuisance tripping. This is a subset of overcurrent device tripping out in general, although the causes are quite different. Another electrical fault involves erratic or immediate tripping out of arc-fault breakers, a problem made more difficult because the fault is often concealed beneath wall or ceiling finish. Just about the only residential circuitry that is at all complex (aside from alarm and low-voltage work) is that involving three-way and four-way switching.
Homeowners who successfully install their own wiring for an addition or garage sometimes become hopelessly confused when wiring these devices, and they call in an electrician to make sense of things.
In addition, at times, the electrician is asked to solve a real or imagined situation of chronic high electrical usage as reflected in the utility bill, and there are instances where this is caused by poor premises grounding. Another culprit could be an individual inefficiently functioning appliance.
A principal troubleshooting technique is half splitting, which was discussed earlier. This method is applicable in residential work, and will quickly take you to the fault. Several tools are useful in residential troubleshooting. The clamp-on ammeter and the loop impedance meter are a great help, as is the circuit analyzer and multimeter, especially in the ohms mode (see Fig. 3-1).
Mentioned previously were some common residential wiring faults. Here they are discussed in more detail with the best troubleshooting techniques.
A Hazardous Situation
Flickering lights are a rather serious problem, and are often a prelude to a catastrophic fire.
The homeowner notices a slight intermittent flicker that at first appeared to be an isolated incident. Gradually, it becomes more frequent and intense, so an electrician is consulted. It is likely that the homeowner has heard, or figured out, that the problem is serious, due to a poor connection that is arcing and could generate enough heat to ignite nearby combustible material. On the other hand, it could be due to a fault in the utility supply, for example, a secondary connection at the transformer in which case the utility should be notified so that they can make the repair.
Since the fault is intermittent, it may not be happening when you visit the site, but most likely you can locate it anyway. To begin, find out the extent of the impacted area. This can be done by observation, if the intermittent is active, or by questioning the occupants. If the flickering is confined to a single cord-and-plug-connected fixture, the homeowner would probably have repaired or discarded it and the electrician would not have been called in. However, it could be confined to a hardwired ceiling fixture controlled by a wall switch.
Before going after a ladder, wiggle the switch from side to side while it is in the ON position. If the flickering responds, you have a bad switch or bad connection at the switch.
Figure 3-1 Inexpensive multimeter.
If there is no reaction at the switch, and the light fixture appears not to contain the fault, and if your power outlets on that specific branch circuit are unaffected, you have to assume that there is fault in a part of the wiring that is concealed behind the building finish- drywall, wood paneling, or other wall or ceiling finish. These are rare, but they do happen.
Has there been recent construction activity whereby an errant nail could have compromised a current-carrying conductor? Alternatively, perhaps a wire was damaged during the initial building, making a local hot spot that finally got worse because of heating at that point.
It is a basic Code principle that spliced conductors, within enclosures, must always be accessible, that is, the cover has to be capable of being removed to allow access to the interior of the enclosure. Junction boxes buried behind wall, ceiling, or other finish were at one time called "blind boxes," but this term is no longer used out of respect for visually impaired individuals (see Fig. 3-2).
Wire nuts in questionable environments should be installed with the openings down so that any moisture will drain.
There are three levels of accessibility: readily accessible, accessible, and not accessible.
NEC defines accessible as capable of being removed or exposed without damaging the building structure or finish or not permanently closed in by the structure or finish of the building. Readily accessible means capable of being reached quickly for operation, renewal,
Figure 3-2, 4×4 box with Romex cable.
or inspection without requiring those to whom ready access is requisite to climb over or remove obstacles or to resort to portable ladders and so forth. The classic example of a location that is accessible but not readily accessible is above a suspended ceiling. Junction boxes are permitted here, and it is an easy task to pop out a panel and peer around to find any junction boxes and service the splices within them.
Splices or terminations that are accessible often cause flickering lights. If there are junction boxes that might contain bad connections, the procedure is to wiggle, probe, and tighten the wire nuts, all the while watching or having a helper watch the load for any reaction.
Sometimes wire nut splices go bad because they were not tightened sufficiently to begin with. Alternatively, especially if there are more than two conductors, they can eventually start arcing if they were stuffed into an overcrowded enclosure--one reason we have box-fill rules. In these instances, the splice can be remade and tightened. However, if there is any sign of oxidation or if there has been flooding or moisture from condensation or a leak, new wire nuts and new wire terminations will be needed. In this connection, it is always a good practice, on the initial installation, to place wire nuts with the opening pointing down, so any condensation or other moisture will drain.
While we are on the subject, some workers wrap electrical tape around their wire nuts.
In my view, it is a bad practice and will probably void the testing laboratory listing. In the first place, those wings and ridges are cooling fins. Tape will hold the heat and cause temperature rise at the splice, which is exactly what you do not want. In addition, the tape adds extra box fill, and that is not good either.
What about twisting the wires prior to putting on the wire nuts? Some electricians are twisters and some are not. I am against that idea also, except for stranded wire or where there are more than three wires where twisting is needed to keep them together. Twisting kinks and hardens the wire so it is difficult to remake the connection if that becomes necessary later. One of the good things about wire nuts is that they can be removed easily for testing and alterations. To make a wire nut splice, just lay the pieces of solid copper alongside each other with the ends perfectly aligned, and let the wire nuts do the work. If necessary, hold the wires with smooth-jawed needle-nose pliers so the wires remain where they belong. When stripping insulation, take off the right amount so that no copper shows when the wire nut has been twisted on and so that there is no insulation inside the metal cone to impede the conduction.
If there is no fault in a junction box, fixture, or switch in the branch circuit, go back to the entrance panel or load center and find the breaker that powers the circuit. Wiggle it and see if the flickering reacts. If so, the fault is invariably where the breaker connects to the bus bar. Arcing and corrosion resulting from the heat conspire to pit and burn the breaker contacts and bus bar. At first, it will be a onetime event, but once the process starts, it invariably worsens, and the heat increases, especially if the load is heavy. Causes of this unfortunate occurrence are moisture in the box, repeated short-circuiting of the breaker, vibration, and running the box with no cover. (The cover helps hold the breakers firmly in place.) A bad breaker should be discarded. It might be possible to clean up the bus bar (with main breaker off) using Scotchpad, but if the pitting is significant, the bad position in the box should not be used. The disadvantage in merely shifting positions, however, is that at some time in the future someone could insert a breaker at the affected position, setting the stage for another event.
When bus bars are damaged in this way, most electricians discard the entire box and install a new one. This is not necessary. Bus bar replacement kits are available for a small fraction of the price of the box. Be sure to get the model and serial number of the old box because there are variations within the same make.
If roughly half the circuits in the building are flickering, it is time to look closely at the main breaker. This is similar to the branch-circuit problem, but far more dangerous because the load is heavier so that there are more electrons trying to squeeze through the high impedance bottleneck. Enough heat can be generated to pass through the back of the box and ignite the wall material behind it. Moreover, an outage that takes place before repairs can be made will put the entire building in darkness or without heat (see Fig. 3-3).
Wiggle the main breaker from side to side to see if the flickering reacts. If the main is bad, there will be a loud frying and popping sound, and light will be seen coming from behind the breaker. If this is happening, it is imperative that the box be de-energized immediately and be kept out of use until the repair is made because there is a severe fire hazard.
In a single-phase main, two hot conductors carry power from the utility. The conductors are usually aluminum rather than copper. Aluminum compounds the problem. (Aluminum is much less expensive; otherwise, copper would always be used.) For a given ampacity, aluminum is always required to be larger in accordance with NEC tables. For example, a 200-ampere residential service calls for 4/0 aluminum or 2/0 copper.
Even in the larger sizes, aluminum is problematic. For very short runs where cost is not a concern, it is better to use copper. For long runs in large sizes, the cost of copper is prohibitive.
Figure 3-3 Circuit breaker box with main disconnect.
The problem with aluminum aside from the ampacity, which is corrected by going to the larger wire, is twofold. For one thing, it is less dimensionally stable; this means that if you tighten a termination, the aluminum will seem to flow. After a couple of years, the lug will appear to have loosened, setting the stage for arcing. Moreover, aluminum oxidizes, especially if there is any heat. The oxide is not a good conductor, so there is impedance and more heat.
One remedy is always to apply an oxide inhibitor such as Noalux upon initial installation, preceded by wire brushing.
It is possible for the entire building to be subject to flickering, that is, for both legs to be affected. This happens when the neutral is arcing. That is less frequent, however, because in the neutral there is less current. The neutral carries the difference between the two legs' currents, since they flow in opposite directions and cancel out each other.
If work is to be done on the main, it is necessary to shut off the power at some point upstream. This is usually accomplished by removing the meter from the meter socket unless there is a separate main disconnect. You have to call the utility and get permission to pull the meter because this involves breaking their seal. (If a meter reader finds a broken seal, an investigation will be initiated to see if someone is stealing unmetered power.) The utility should give you a plastic shield, which is used to cover the live parts inside the meter enclosure. The uncovered meter socket, with live upper lugs, should never be left untended.
With the meter removed, there will be no power on the main, and it will be safe to replace the entrance panel and remake the connections.
In some instances, the entrance panel including main breaker will not be at fault. A loose connection in the meter socket or weatherhead is rare, but sometimes occurs. There can be a fault at the transformer secondary. Utilities define the customer's point of connection, and this varies in different areas, so upstream from the main breaker it is necessary to check with them to see who is responsible for the repair.
Sometimes it is difficult to find the location of the fault when there is an erratic leg. One clue is to see if the flickering occurs when the wind is blowing, which would indicate a service-drop conductor (Triplex cable) rubbing on a tree limb. Another good method for narrowing down the location of a fault when the flickering is active is to connect a voltmeter to the input of the main with the main breaker off and see if you get fluctuations. Using common troubleshooting techniques, you can find the bad connection and correct a very hazardous condition.
Before commencing work on a light fixture directly over a sink, close the drain. If a screw or small part is dropped, it will not be lost.
We mentioned that three-way and four-way switching could be a challenge for homeowners and beginning electricians. Many times the mistake is in the neutral. The purpose of three-way switches is to permit operation of a load, usually a ceiling fixture, from two separate locations. Examples are a room with two entries at opposite ends, a stairway with one three-way switch at the top and one at the bottom, and a detached garage with the lighting capable of being controlled in the garage or in the house. Any number of additional control locations is possible by adding four-way switches between the pair of three-way switches.
In wiring three-way switches, several configurations are possible, depending upon the layout of the room. The most basic setup is when power, from an entrance panel or load center, is delivered to a wall box enclosing the first three-way switch. Cable from a different knockout in this box is run to a wall box housing the second three-way switch. Cable from a second knockout in this box runs to the light fixture.
A Thought Experiment
The best way to think about the two three-way switches is as a "black box" that functions as a regular single-pole switch. A black (hot) conductor feeds one terminal, the input, of this imaginary composite switch and a black conductor (switched hot) is connected to the output of the switch and powers the light fixture when the switch is in the ON position.
White, the neutral return from the light fixture, runs straight through from the light fixture back to the power source. It is never connected to a switch, although it is spliced with wire nuts in both boxes.
What makes a pair of these switches different is that the two parts of the black box are in separate locations, so the two three-way switches have to be wired together. 2011 NEC ampacity tables provide for small loads, up to and including 15 amperes, to be supplied by 14 AWG conductors. However, many electricians feel that this wire is too small even for these residential branch circuits, and they use 12 AWG copper. Alternatively, maybe it is that they want to have a more consolidated inventory. For whatever combination of reasons, 14 AWG is not always used where permitted. Despite the practice, 14-3 AWG is used usually to wire from one three-way switch to the next. (Three conductors are required, so that what is needed is 14-3 AWG with ground. In this numbering convention, the equipment grounding conductor is not counted, so 14-3 AWG actually has four wires, and 12-2 has three. Throughout these discussions, it is assumed that the equipment grounding wire will be connected at each device.) Three conductors are required between the two three-way switch boxes. The red and black are two alternate ungrounded current paths, and the white is either the grounded neutral or the switch-loop return, in which case it is reidentified black, as explained next (see Fig. 3-4).
The red and black of the 14-3 AWG are called "travelers," but I call them "politicians" in order to inject a little humor into an otherwise dry topic.
The position of the first three-way switch (up or down) determines which of the politicians is energized, and the position of the second three-way switch determines whether the load is energized. Thus, the switch handles in the ON position will alternate between being up and down, so they are not labeled ON or OFF.
That is all there is to it, except knowing how to terminate the wires at the three-way switches. A three-way switch always has three terminals (not counting the equipment grounding terminal) and the screws have a brass or dark finish, not silver. What can be confusing is that one of these is labeled "common." We usually think of a common terminal as connected to one input and one output wire, these being joined so that two wires can do the job of three. For three-way switches, this is not the case. The common terminal of the first three-way switch is connected to the incoming black (hot) wire from the entrance panel ...
Figure 3-4 Three-way switch schematic.
... or load center. The common terminal of the second three-way switch is connected to the outgoing (black) wire that goes to the load. You will notice that this common terminal is located at one end of the switch body and the two terminals that connect to the red and black politicians are at the other end. If you come across a three-way switch that is constructed differently, you can identify the terminals by ringing out the switch with an ohmmeter.
As for the other configurations, it is sometimes desirable to bring the branch-circuit power directly to the light fixture, and wire the two three-way switches as if they were one single-pole switch loop. For this procedure, 12-2 cable is run from the power source to the fixture, where the neutral (white) connects to the appropriate terminal. Remember that the neutral from the power source always connects to the neutral terminal of the load, without any involvement with the switching, except that in the first configuration, it passes through the switch boxes.
In the segment of 12-2 cable that goes from the fixture to the first switch, the white is not a neutral. It is the return conductor of the switch loop of which the two three-way switches are a part. The white conductor is to be reidentified as black at both ends. This marking may be done with paint or black tape. It must completely encircle the conductor. Some electricians make three rings of tape, but just one is compliant. Colors other than black are permitted for the switch loop, but not white or green. All of this assumes that the residential building is being wired in Romex, as is usually the case. If it is being wired in electrical metallic tubing (EMT) or other raceway, the correct colors will be pulled in the first place, and reidentification will not be necessary.
A third configuration is when line power is run to the second three-way switch. In this situation, 12-2 is run to the fixture, the white being the neutral and the black being a switched hot. Here are a few points to keep in mind:
• The fixture always requires a white (neutral) wired directly back to the source and never switched, although in cases where power is not run initially to the fixture, the neutral will be spliced in one or more of the switch boxes.
• When power is initially run to the first switch, the whites are all neutrals.
• When power is initially run to the light fixture, the whites are all switch-loop returns, and are reidentified black.
• When power is fed to the three-way switch that is closer to the light fixture, the white conductor that is part of the 12-2 cable is neutral. The white conductor that is part of the 14-3 cable is a switch-loop return, and is reidentified black.
• The red and black that are part of the 14-3 are called travelers or politicians, and they are connected to the two terminals that are opposite one another at one end of the three-way switch bodies. It does not matter which is red and which is black, but they are never connected anywhere else. To the single terminal at one end of the switch body (labeled "common"), you connect only a black (hot) wire of the 12-2, or a white switch-loop return of the 12-3, which is reidentified black.
The pair of three-way switches described above permits the user to operate a load from two locations. Any number of additional locations can be added simply by installing four-way switches between the three-way switches. The four-way switches are simpler to wire than three-way switches. They have two input terminals at one end of the switch body and two output terminals at the other end. The four-way switches go with the politicians-a red and a black at each end. It does not matter which is red and which is black, nor does it matter which end of the switch is the input and which is the output. A white conductor is never connected to the four-way switch.
With the above principles in mind, you will never have a problem figuring out how to wire these switches, and you will be able to help the unfortunate homeowner who has become hopelessly confused or the beginning electrician. Most residences have two or three pairs of three-way switches. Four-way switches are rarely used, but when called for they are a worthwhile enhancement.
Ground-fault circuit interrupters (GFCIs) are used extensively in residential and other installations. Since their introduction in the 1970s, each Code cycle has mandated additional locations where their use is required, and with good reason. These simple devices are great lifesavers as they provide excellent protection from line-to-ground electric shock (see Fig. 3-5).
A GFCI may take any of several forms. One type is a GFCI circuit breaker. It occupies a breaker position in an entrance panel or load center and provides conventional branch circuit over-current protection as well as GFCI protection. Like all GFCIs, it protects all downstream wiring, but has no effect on the upstream wiring. This device inputs its power from the busbars of the box, and has a terminal screw for the output. Additionally, a white pigtail is connected to the neutral bar. Like all GFCIs, there is a test button to check that the device is working properly. The installation is simple and the protection encompasses the entire branch circuit, so these devices are quite good but, unfortunately, they are costly, and for this reason their use is limited.
The most common GFCI takes the form of a duplex receptacle, available in 15- and 20-ampere ratings. These devices fit in a deep wall box and take a special wall plate that has a large rectangular opening. They have test and reset buttons and the newer ones have LEDs that indicate tripped status, which is a good feature.
These GFCIs also have feed-through capability. Black (hot) and white (neutral) wires from the source are connected to terminations marked LINE. Two other terminations are marked LOAD, allowing downstream non-GFCI receptacles to be daisy-chained as needed.
These receptacles also have GFCI protection. The GFCI comes with labels marked GFCI PROTECTED that may be affixed to the downstream receptacles.
Figure 3-5, Ground-fault circuit interrupter.
An interesting property of a GFCI is that it does not require an equipment grounding connection in order to function. In fact, a GFCI is a Code-sanctioned replacement for a receptacle that lacks means for an equipment grounding connection. Another type of GFCI is for cord-and-plug-connected portable electrical equipment that could present a hazard because it operates in a wet environment. An example is an electrically powered pressure washer. The GFCI is an integral part of the cord, close to the plug, and it also has test and reset buttons.
All of these GFCIs work the same-internal circuitry compares the incoming current on the black (hot) wire to the outgoing current on the white (neutral) wire. When the equipment and associated wiring are working properly, the difference between these two currents is zero. However if, due to faulty insulation or water infiltration, some electrons go to ground so that there is less current going back to the electrical supply than coming from it, a hazardous situation could occur and the GFCI trips out. Typically, a power tool such as a portable electric drill will develop loose bearings and the armature will rub on the housing. Alternatively, an internal wire, often where the cord enters the enclosure, will chafe and short against the metal. Either way, the housing will become energized. If it is grounded via a low-impedance path back to a good grounded service, the overcurrent device will trip, protecting all concerned.
However, if there is a weak link in the ground path (as when someone has sawed off the ground plug), the housing will remain energized. If someone takes hold of it while standing on a damp surface, that unfortunate individual will become the ground path and could be killed.
That is where the GFCI comes in. Sensing the missing electricity that is not returning to the power source via the neutral conductor, the GFCI instantly shuts down the circuit. These great lifesavers are Code mandated for many indoor and outdoor locations. "Residential" and "commercial" are not NEC terms. Instead, there is frequent reference to "dwellings" and "non-dwellings." The latter would include commercial and industrial locations, so the meaning is broad. GFCI requirements differ markedly depending on location. As an example, in the kitchen of a non-dwelling such as in a restaurant, all receptacles must be GFCI protected, whereas in a dwelling only the countertop receptacles and those within 6 ft of a sink must meet this requirement.
Nuisance Tripping
Because of their great sensitivity, there is a certain amount of nuisance tripping, and often the electrician is called in to solve the problem. It is one of the more common troubleshooting tasks. The procedure is not complex, but homeowners are perplexed and often need help.
There are three probable causes of GFCI tripping: faulty electrical equipment connected to a GFCI-protected circuit, faulty wiring associated with the circuit, or a faulty GFCI device. The fault has to be the device or downstream of it. Nothing that happens upstream can cause the GFCI to trip out.
The first step (after interviewing the homeowner for possible clues to the location of the fault) is to discover the extent of the affected circuit. To do this, hit the test button of the parent GFCI and find which downstream receptacles are dead. Look at the layout of the rooms with respect to the entrance panel or load center and think how you would run the branch circuit. This will help you to figure out which receptacles are fed by the GFCI. In large subdivisions where a few dollars saved here and there will affect the worth of the electrical contracting company over the years, it is common practice to bug an outdoor receptacle off a bathroom parent GFCI. This can be baffling for those who are not aware of this detail. In addition, it is possible that not all GFCI-protected conventional receptacles are labeled.
One at a time, unplug any pieces of electrical equipment to find if one of them is at fault.
It could be as simple as a laptop charger or a gas stove with electronic igniter and clock. If it is not one of these, divide the string of paralleled receptacles in half by breaking the circuit at midpoint. You can disconnect the black wire only. See if the fault persists. Continue subdividing until the fault is found. It can be in the receptacle, in the wiring within the box, or in a concealed portion of the wiring between boxes. If it is in the concealed wiring, you have some work to do, either fishing new wire or running Wiremold. Such problems are the downside of GFCIs, but the lifesaving benefits outweigh such aberrations.
Just as GFCIs protect against electric shock, the more recent arc-fault technology shows great promise in the prevention of electrical fires. Electrical fires cause far more fatalities than electric shock does, so any innovations along these lines are certainly beneficial.
Electrical fires have various causes. Faulty design or initial installation can result in gross over-fusing so that at a critical amount of loading the branch circuit wires become red hot within the wall. Neglecting to use corrosion inhibitor for aluminum connections at a service is another cause, and still another is overheating of a motor or other electrical equipment, perhaps caused by accumulation of dirt and debris that block air circulation. An arc-fault circuit interrupter prevents none of these.
Unlike a GFCI, an arc-fault device is sensitive to upstream and downstream faults.
However, it only protects the downstream portion of the wiring. An arc fault is caused by a loose connection, partial break in the wiring, or other failure mode that is characterized by rapid and sharp variations in the current flow. It is a sputtering, buzzing sort of phenomenon, and the arc-fault device has internal circuitry that detects this aberration in the current that flows through it, immediately interrupting the power supply. Recent Code cycles have greatly expanded areas where its use is mandated in dwellings. If an arc-fault device is tripping out, avoid the temptation to swing over the supply wiring to a non-arc fault device to restore service, as this leaves the latent fault in place, setting the stage for an electrical fire down the road. Troubleshooting and repair procedures are similar to those for GFCIs that are nuisance tripping. Sometimes a lot of work has to be done to clear the fault, but this goes with the territory.
A frequent homeowner complaint is high electricity usage as reflected in the utility bill, and here again an electrician is consulted. There are several ways the situation can be resolved. One answer, of course, is that an appliance is consuming an abnormal amount of power. As they age, motors begin to run slower and draw more current. Other types of electrical equipment can become big energy consumers as well, so once more we begin by entering an information-gathering mode. At times, the power-hungry appliance will be seen to function in a strictly steady-state fashion, drawing the same amount of current at all times. On the other hand, the consumption may be intermittent, fluctuating rapidly because of a poor connection, switch, or faulty heating element. Still another pattern of excess power consumption is that it is long-term variable. The current level will be time-dependent, with gradual changes keyed to an 8- or 24-hour period. This is caused by varying power usage of other electrical equipment that may be on the same premises or outside. Nevertheless, a fault in the unit under consideration is causing it to be vulnerable to this malfunction.
No matter the cause, measurements are in order. For steady-state excess current draw, the clamp-on ammeter is the perfect diagnostic instrument. If the appliance is alone on the branch circuit, you can find a single conductor to enclose in the jaws of the meter within the breaker box. If it is a hot water heater, the thermostat (temperature knob) and timer, if any, will have to be set properly. Record the ampere reading and verify that the thermostat shuts off the power supply after the temperature comes up. Of course, the whole problem could be a hot water leak or dripping hot water faucet. Compare the ammeter reading to the nameplate rated current and see if it is abnormally high. Electric hot water heaters usually have two elements of different wattage ratings. They are controlled separately by the thermostat and the setup can be changed by shifting terminations. Sometimes an element will burn out (become open) and this will cause the thermostat to feed power to the other element for an inordinately long time.
An Easy Job
An element resembles an incandescent light bulb but with a very heavy iron filament and no glass envelope. The element must always be immersed in water or it will instantly burn out. For this reason, usually the top element burns out. Either element can be checked in place with an ohmmeter. It is an easy job to change an element. With power locked out, drain the tank. Unhook the two wires from the element and unscrew it. If the gasket is damaged, it will have to be replaced. Hot water heater elements are inexpensive and generic elements fit various makes. Be sure to refill the tank before applying electrical power.
If an incandescent light fixture will not work with a good bulb in place and power coming in, it is possible that the center spring terminal in the light socket has lost its tension. With power off, grab the "piton" with needle-nose pliers and give it a good pull.
This often works on old fixtures.
Electrical equipment that is drawing intermittent or variable amounts of power can be monitored by means of a clamp-on ammeter that has a hold function. The meter can be left overnight or longer, to record peak power consumption. In this way, all appliances, branch circuits, and so on can be checked for inefficient operation.
Another cause of excessive electrical consumption is poor grounding. An inadequate ground can cause unstable voltage in the two legs of a single-phase service, and for a variety of reasons it should be corrected. The problem can be in the grounding electrode or the grounding electrode conductor.
Just about all residential services are grounded by means of two ground rods driven at least 6 ft apart. If they are closer, the two cylindrical-shaped charged regions in the ground interfere with one another, making for a weak grounding electrode system. The goal is to achieve a low-impedance connection to the earth. Besides ground rods, ground rings, ground plates, rebar in footings, and other grounding electrodes are effective, and specifications for them are given in the Code. Buried waterline, especially connected to a well casing, is an excellent grounding electrode, but unfortunately from the point of view under discussion the trend toward increased use of plastic pipe means water pipe grounding electrodes are no longer as reliable as they were at one time. You never know when a break in the pipe will be repaired with plastic, breaking ground continuity.
The NEC requires, when a ground rod is installed, that the ground resistance be measured and that it be not more than 25 ohms. However, this measurement cannot be made with an ordinary ohmmeter, as this would require a known perfect ground, and then there would be no point in the whole exercise. Ground resistance can be measured with expensive specialized equipment, but the Code, in an exception, provides that the measurement need not be taken if a second ground rod is installed, and this is how 90 percent of the residential services in new construction are built.
A certain amount of common sense is needed. Good grounding is dependent upon moisture content of the soil. Dry gravel in an arid region makes for a high ground resistance. The best plan is to place rods right in the drip line of the roof runoff. As mentioned, a 6-ft minimum distance between the two ground rods is required, but why not go farther for the price of a few feet of wire? The ground wire should be bare copper, buried below the drip line. The ground rods should be driven deep enough so that the tops, with ground rod clamps, are below grade. If bedrock is encountered, never saw off the ground rod. It may be driven at an angle or laid level as deep as possible.
If you suspect poor grounding is the reason for high meter readings, you can enhance the grounding system by adding extra electrodes, perhaps constructing a ground ring. In dealing with this problem, a utility engineer should be willing to visit the site for consultation.
These are some of the principal troubleshooting issues encountered in residential electrical work. Most of the troubleshooting in this setting involves an initial interview with the owner, the endeavor being to discover the exact nature of the problem and whether it was preexisting or arose in response to some specific event. It is surprising how often the user can supply a bit of insight that will lead you to a solution. Then, use the half-splitting technique to progressively narrow in on the defective component or device, and that should lay the foundation for a successful repair.