The Circuit Detective    -  Electrical Malfunction - Why?

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How a Home's Electrical Can Malfunction

How Things Go Wrong

Why should a system which has few moving parts be subject to failures of various kinds? Realize that every technology designs its systems with economy in mind. Even the best available wire connector, for instance, could have been made from even better materials that would have made problems with it even less likely.

Also, there is such a thing as wear and tear on electrical components. Current flowing through wires and connections creates heat and other stresses that affect the quality of insulating materials and the conductivity of metal surfaces. Add to this the effect of repeated use -- where plugging and unplugging appliances at a receptacle gradually loosens its hold on the prongs being plugged into it -- and you begin to see what can happen.

Besides these there is the matter of workmanship. The reliability of the system depends on the care taken to set it up, from the engineers designing a switch to the person installing it. How tight should a screw be that holds a wire in place? This is something ultimately learned by experience, even though a manufacturer may specify what torque should be applied.

And finally, any time your system is reworked even slightly, there is room for error -- from ignorance or unintentionally.

So both the human and the material worlds contribute to the malfunctions this website is trying to pick up after. The need for home electrical troubleshooting is built in.

What are the kinds of things that could possibly go wrong in your electrical system? Let's consider two ends of the spectrum. At one end, you are familiar with a light bulb burning out. On the other end, you have experienced times when neighborhood power to your home has been interrupted -- briefly or for a number hours. Between these, there are quite a variety of other ways.

To grasp the scope of possible problems, and to lay a groundwork for a strategy to solve them, we will consider the relation between symptoms and causes. (First you might want to see if you have a basic grasp on a home's Electrical system.) We can categorize what goes wrong by the symptoms produced or by the cause, and these two aspects are related to some degree, as will be illustrated soon in a chart. First, consider the possible symptoms:

Symptoms Spelled Out:

1. Does not work. Some things don't work. This is the most common malfunction.
2. Goes on and off at will or blinks or flickers. Things are working now but in the past some things have gone out for awhile and later come back on their own.
3. Runs dim or bright sometimes. Lately, things often dim down or brighten at will or in response to turning something on or off. This goes on for more than three seconds at a time. This category is to be distinguished from the previous one.
4. Won't go off. Something won't turn off by means of its switch or other control device.
5. Shocks. Someone experienced a shock.

Now see the relation of these symptoms to their possible causes:

S Y M P T O M
CAUSE: Does not work Goes off and on at will or flickers Runs dim or bright sometimes Won't go off Shocks
Short/Ground-or-arc-fault/Overload Yes -- -- -- --
Circuit (or main) wire connection poor ("open") Yes Yes partially Yes -- --
Ground-fault without an intact intended ground path -- -- -- -- Yes
Miswiring Yes -- -- Yes Yes
Bad or mis-set device Yes Yes -- Yes --
Open in new window

Causes Spelled Out:

1. Overload/ Short/ Ground-fault/ Arc-fault. I group these four causes together because they are ultimate causes whose immediate causes are tripped breakers, blown fuses, or tripped GFIs or AFCIs. Let me distinguish the four. An "overload" occurs when in its normal operation a circuit has carried a little too much current a little too long, so that the wires will be getting too hot, and so the breaker trips off to prevent this. You were running a little too much on that circuit. A "short" is an unintended connection from a hot wire to ground by way of the neutral wire or (less technically) by way of the ground wire or anything providing a path to the earth. A short will usually trip a breaker because the flow of current is potentially huge, not being limited and safe by design, as it is when running lights and appliances. Current still flows around from the ungrounded starting point to the grounded end point, and so it is still technically going in a "circuit". A particular short (in the broad sense) is the "ground-fault". It involves contact from a Hot wire to something grounded other than the neutral itself; if there is a ground-fault interrupter device (GFI) ahead of it on the circuit, it will sense this and trip off. Even when a ground-fault is not strong enough to trip a normal breaker it is a hazardous "leaking" of current off of the intended path. An "arc-fault" can be a short or a ground-fault, but of a particular kind -- one in which there is irregular resistance to current flow, resulting in sparking (arcing). Sparking along the normal wiring-path of current is another form of arc-fault, called series.
2. Circuit or main wire connection open. An "open" (see definition) refers to an unintended discontinuity somewhere along a circuit's path. It may be a break, a gap, or a deterioration. Typically, a wire has become too loose at a point where it is supposed to pass current on to another wire. Bad electrical connections diagram This first diagram shows the places that can develop an open. The second is a closer look at what is behind some bad connections. Wirenut, quickwire, sidewire, and pigtail diagram- thumbnailSee a photo of what Bad connections occasionally can look like. An open at a main wire -- at the panel, meter, or line from the power company -- will disable more than one branch circuit. Video. In addition, it will affect several circuits in unusual ways. The combined 120 and 240 volt system provided to U.S. and Canadian homes is behind this weird Dimming or brightening effect. (Here is a site that explains the Systems in other countries). A similar effect can appear in the case of an open neutral of a Two-circuit cable.
3. Ground-fault without an intact intended ground path. Shocks become possible when a person's body provides the unintended path for a hot (faulting) device, fixture, or appliance toward a grounded wire, device, fixture, appliance, pipe, or to the earth itself. Whatever should have grounded the hot item is either missing or out of contact with it (is open); otherwise it would have tripped a breaker.
4. Miswiring. Poor workmanship can result in the other cause-categories, but this one refers to actual mistakes made in connections, often when a device is replaced. See Replacing devices and Correcting connections.
5. Bad or mis-set device. Switches, outlets, light fixtures, and light bulbs can fail to operate as they should because of breakage, arcing, heat, internal wear, damage, corrosion, or manual settings on them that have been changed. This cause will tend to affect only the thing itself or, in the case of a switching device, the things meant to be controlled by it.

If you have checked your understanding of your electrical system at the main Background page, you may now be ready to attack your household electrical problem using my step-by-step Troubleshooting Strategy Pages. If you can't afford an electrician and are a little bit handy, I think you will find my electrical advice clear and helpful.


"Thanks for creating such a great and free resource for homeowners like me. Your experience really shines through your advice. Keep up the great work. I may be needing your help because I have a breaker that won't stay on. I have spent 5 hours already, ripping open every junction box on that circuit. Cheers," -Chris

"I thought we were going to have to dip into the Disneyland vacation fund to have an electrician come out and fix two circuits, but I did it myself with the simple instructions on your website. Thank you!!" -Scott, CA

© 2005-2013 Larry Dimock

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