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What Causes Electrical Fires in the Home

Home electrical fires are preventable, but each year produces thousands of such fires.  Don't let it happen to you, particularly in the Christmas season as cords and lights are strung everywhere.
Home electrical fires are preventable, but each year produces thousands of such fires. Don't let it happen to you, particularly in the Christmas season as cords and lights are strung everywhere. | Source

Electrical Fire Causes

Unfortunately, home fires are an all too common occurrence and in a great many cases the root cause is an electrical failure of some kind. The causes of electrical fires are many; sometimes it is mechanical failure of an electrical device and sometimes it is from improper usage or design of the electrical system in your home.

Nearly all electrical fires can be prevented, though, if we understand the causes of electrical home fires and take appropriate steps to prevent them. A little added convenience, saving a couple of dollars - these things aren't worth risking the loss of your home or life from a fire.

The National Electrical Code (NEC) is widely accepted throughout the US as the definitive standard for electrical work and a good portion of that code consists of procedures to prevent fire. As a professional electrician for many years I am expected and required to understand and comply with the guidelines of the NEC at all times and that typically means an understanding of why those rules are in place.

The "bible" of electrical work.  Follow it and you will have a good, safe electrical system.
The "bible" of electrical work. Follow it and you will have a good, safe electrical system. | Source

The NEC's Role in Home Fire Prevention

The NEC, some 800 pages describing proper methods of doing nearly all electrical work, is just a small part of the NFPA - National Fire Protection Association. It is not designed to produce efficient electrical systems nor to make profits for the inspectors enforcing the rules. It is not intended to sell particular electrical devices and it will not describe how to wire a house cheaply or quickly. The only reason for the code is safety - all 800 pages describe how to install electrical systems that will operate safely and this includes fire prevention.

For example, table 310.16 in the 2008 code lists the minimum wire size for a given circuit breaker or fuse - in the table we can see that a 20 amp breaker requires a 12 gauge wire. This isn't because a smaller 14 gauge wire won't work, it is because a 12 gauge wire will carry at least 20 amps of current (with a considerable safety factor) without overheating and causing a fire. If your home is wired with 14 gauge wire (most homes are) but the breaker keeps tripping it is not only illegal but very risky to replace it with a 20 amp breaker. That 14 gauge wire can now overheat before the breaker trips and cause a home fire, and that's the first lesson for the homeowner - never make changes to the electrical system in an effort to bypass the safety devices installed.

GFCI outlets, circuit breakers, fuses, arc-fault breakers - all of these can be irritating at times but they are there for a very good reason - your safety and the safety of anyone in the home. They are designed to shut the circuit off before either a fire or shock can cause any harm and should never be removed, modified or defeated in some manner.

In years past homeowners with screw in fuses rather than modern circuit breakers used to remove the fuse, stick a penny in and screw the fuse back in. Any and all protection afforded by the fuse is completely lost as a result and overloaded circuits will simply heat up until they either melt the wire in two or (more likely) cause a fire. Such modifications all too often have literally deadly results.

Poor Electrical Connections Can Cause a Home Fire

Any time electricity flows it creates heat. Under normal conditions, this heat is minimal - your home wiring is designed and installed to prevent any large amount of heat build up in the electrical system. Sometimes, though, failing equipment or devices create far more heat than they are designed to. Some examples might be:

Loose or Worn Outlets

Loose and worn outlets. If cords can be plugged into an outlet very easily or if they simply fall out as time passes, the outlet needs replacement. If appliances plugged into an outlet operate only intermittently it can be caused by poor connections either in the outlet itself (outlets with wires plugged into the back of them instead of being secured by a screw will fail with time) or in wire nuts in the box behind the outlet. Either tighten the wire nut connections and/or again replace the outlet.

Worn Switches

Like outlets, switches will wear out over time. They will usually last for many years, which makes it easy to think they will last forever, but they won't. Just like outlets, the wire connections in the back or side of the switch may be loose and, again like an outlet, the switch needs replacement. It is also possible that wire nuts are loose behind the switch.

Old and Corroded Fixtures

As electrical parts age the wiring degrades very slightly each year. A light fixture may be good for 25 or even 50 years, but eventually the wire insulation inside chars, the connections corrode and the light bulb sockets won't hold a bulb well. If lights flicker or won't stay lit and potential switch problems have been eliminated it may be time to replace old light fixtures.

The spring that holds the wire in the small hole weakens over time and makes for a poor electrical connection.
The spring that holds the wire in the small hole weakens over time and makes for a poor electrical connection. | Source
Changing this flickering light fixture found the old wire to be charred at the ends of the wires with both wire nuts loose.  A fire waiting to happen.
Changing this flickering light fixture found the old wire to be charred at the ends of the wires with both wire nuts loose. A fire waiting to happen. | Source

Other Electrical Problems That Can Result In A Fire

Extension Cords

The use of extension cords should be evaluated for necessity; they are a very common cause of home fires. When a cord is kinked or smashed (walking on it too many times, for instance) the electrical resistance of the wire inside rises, which creates heat. Eventually the insulation may well begin to melt but this is not obvious; it may just be a small portion between the copper wires inside. As this happens more and more current begins to flow between the wires and eventually causes a fire. If you absolutely must use an extension cord for long periods of time make sure it is completely out of the way and not subject to physical damage. Under a couch, perhaps, or tucked into the edge of carpeting - whatever it takes to make sure that feet, vacuum cleaners, pets and small children can't reach it. Better to simply add a new outlet to an existing one than use an extension cord for months or years.

Continual Overloads

Many older homes are really marginal in their ability to safely provide enough power to operate all the electrical things we use in modern life. There just isn't enough power available to the home or there aren't enough individual circuits. In years past only one circuit was designed into kitchens, and that isn't enough to properly operate a microwave, refrigerator, toaster, electric grill, mixer, toaster oven, etc. The result is that the circuit breaker or fuse is always tripping. The same is true in bathrooms; the bathroom circuit commonly supplies bedrooms as well, but add in a curling iron and a hair dryer along with the bedroom TV and electric blanket and that circuit is often overloaded as well.

Every time a circuit trips or a fuse blows it is an indication that the circuit is overloaded, but most people will simply reset the breaker and do it again. The inevitable result is that the circuit breaker is slowly damaged to the point it doesn't work properly anymore and the panel itself can be damaged as well. As an electrician, I've seen house panels that have the massive bus bars inside, carrying the entire power for the whole home, half melted from repeated overloads and this is a recipe for disaster - it most certainly is one way that home fires start.

If you are commonly tripping a breaker or having to replace blown fuses, have additional circuits installed as necessary. It can be expensive but it's better than burning the house down.

In addition to electrical overloads is overloading a light fixture with lamps that are too large. According to the NFPA, the largest source of electrical fires are lamps and light fixtures. Such fixtures are designed to withstand only the heat from the rated size light bulbs - do not overload the fixture with bulbs that are too large. While it is quite acceptable to use a 100 watt equivalent CFL bulb to replace a 40 watt incandescent bulb as an energy saving measure in your home, the key is that the CFL is only using a few watts of energy and isn't nearly as hot. It won't overload either the thermal insulation or the electrical wiring of the fixture. It isn't the same as screwing in a 100 watt bulb into a 40 watt light.

Defective Equipment

Occasionally equipment of various kinds can fail in such a way that it may not trip a breaker or blow a fuse, but is still drawing more current than it should. Circuits in general are allowed to carry only 80% of the current the breaker will allow as a safety factor but when that is removed the safety becomes marginal. While the current may not trip a breaker, it does cause heat and, over time, can harm the electrical components such as breakers or the wire itself. Eventually resistance rises to the point that enough heat is produced to cause a fire.

If a fan, for instance, turns too slowly, if the cord warms to the touch, if it makes strange noises - replace or repair it! Don't simply keep using it until the cord catches fire. Electrical heaters are equipped with a "tip over" switch that turns them off if they are tipped over - never, ever defeat such electrical protections. They can be irritating, but they also save lives.

Improper Wiring Methods

A qualified and conscientous electrician will always follow the requirements of the NEC to produce a safe and effective electrical system, but the same isn't true of homeowners who often don't know what is safe. Another example from my experience: I once purchased a used hot tub from a homeowner. Upon finding that I was an electrician, he asked me to unwire it from the house and I agreed to help him out there. He had run wire from the hot tub to a dryer outlet just inside, but what appeared to be adequately sized wire turned out to be 14 gauge wire wrapped with many layers of electrical tape. Now, that is at least 3 sizes too small for the hot tub and when I removed the large cover from the dryer outlet it simply crumbled in my hands - completely charred to nothing but tiny bits of plastic just waiting to be disturbed to fall apart. The homeowner looked at it, looked at me, and commented that "I guess that's what causes fires, huh?".

He was right - that's what burns homes down and it was completely unnecessary. If you don't know what is needed to complete a wiring job safely, either find out or hire someone that does know. Electricians have, in most states, completed years of study and work learning how to ply their craft and are usually quite knowledgeable. Hire one if necessary.

Holiday Decorations

Holidays often bring home fires with them. Extension cords are strung everywhere, lights are added all over rooms and vegetation outdoors, and even candles are left burning without supervision. All of these are dangerous and can cause a home fire at the worst possible time. Make sure that your Christmas tree isn't drying out with lights or candles still on it. Put candles out when you're not right there. Protect extension cords, and particularly don't leave the ends of them in puddles or snow. Arrange cords so that children or pets can't play with them; a dog chewing a cord cannot only electrocute themselves but can burn the house down as well. A little common sense can go a long way.

A damaged extension cord.  Either replace or repair properly - never simply throw some tape on it.
A damaged extension cord. Either replace or repair properly - never simply throw some tape on it. | Source
Older homes weren't wired with modern small appliances in mind.  Be cautious about using more than one at a time.
Older homes weren't wired with modern small appliances in mind. Be cautious about using more than one at a time. | Source
This air compressor needs some work where the wire enters the control box; it will eventually be damaged from vibration if not clamped properly.
This air compressor needs some work where the wire enters the control box; it will eventually be damaged from vibration if not clamped properly. | Source
A properly wired shop fixture.  The inset photo shows one without a cable clamp; the wire will eventually be cut by the sharp edge of the fixture.
A properly wired shop fixture. The inset photo shows one without a cable clamp; the wire will eventually be cut by the sharp edge of the fixture. | Source

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Comments 24 comments

SimeyC profile image

SimeyC 4 years ago from NJ, USA

Very informative and well written - hmmm I better call the wife I have one switch that needs replacing I think!


theraggededge profile image

theraggededge 4 years ago from Wales

Invaluable information that everyone should read!

Here in the UK, we have a contract with our energy providers to inspect and repair our electrical and heating systems. It's an added cost but one we are happy to pay.


ThePracticalMommy profile image

ThePracticalMommy 4 years ago from United States

This hub is incredibly useful, especially for a homeowner of an older home, like myself. I know there is much electrical work needed in this home done by an experienced electrician. I have fears that the previous homeowner did much of the electrical work himself without knowing how to do things properly and someday there may be a fire due to that. Time to call an electrician!

Thanks for the info! Voted up and useful.


LauraGSpeaks profile image

LauraGSpeaks 4 years ago from Raleigh, NC

Very informative! Voted up.


angela_michelle profile image

angela_michelle 4 years ago from United States

This was very informative and information I did not know before. Great job!


GoodLady profile image

GoodLady 4 years ago from Rome, Italy

I live with a great electrician so he saves me from myself, but without him I'd certainly need to print this up and keep it as my guide. It is so well put together and so very helpful, explaining the whys and wherefores of electricals.

Voting up


Austinstar profile image

Austinstar 4 years ago from Somewhere in the universe

I did not know you were one of those magical electrical guys.

Great informative hub. Loved the photos too.

Is it hard to wire an out building, like a storage shed to a home? I want a storage shed for use as a spa room. Of course I'll have to wire it. Or rather pay some magical electrical person to do it.


GusTheRedneck profile image

GusTheRedneck 4 years ago from USA

Hi Wilderness - One of the things that folks have to look out for is aluminum wiring. Most of that is probably already replaced or burned out, but the connections degrade due to the forming of aluminum oxide at joins.

Thanks for the useful article.

Gus :-)))


wilderness profile image

wilderness 4 years ago from Boise, Idaho Author

@Gus; you are absolutely right, and the poor connections that are the result of that oxide are an electrical fire hazard as well.

Good catch!


chrissieklinger profile image

chrissieklinger 4 years ago from Pennsylvania

Friends of ours had a house fire due to a dehumidifier malfunctioning and luckily they were not home at the time. Many people don't realize all the things you have plugged in when you are not home. Thanks for writing this easy to read but very informative article!


denisemai profile image

denisemai 4 years ago from Idaho

The outlets that are loose or falling down is of concern to me. I live in a fairly new house but some of my canned lights are hanging below the frame. I'm wondering if the electrician did a shoddy job. I'll have my husband look at it. Good article and very timely with the approaching holidays.


Just Ask Susan profile image

Just Ask Susan 4 years ago from Ontario, Canada

When we bought our home it had all the old knob and tube wiring. In order to get home owners insurance all had to be replaced so out it all came. We also added a 200 amp service.


weestro profile image

weestro 4 years ago from Virginia

Great hub, thanks for the tips!


wilderness profile image

wilderness 4 years ago from Boise, Idaho Author

@denisemai; those can lights may be nothing to worry about; many simply push up into the framework and can work loose over time, allowing them to drop from the ceiling to the point that the wire is all that is holding them. Simply push them back up into the ceiling.

@Just ask susan: Good choice - I've seen many older homes still using the old knob and tube wiring with no problems (outside of the fact there is no ground), but have always been afraid of it.


Will Apse profile image

Will Apse 4 years ago

I routinely freak out at the electrical set ups in Thailand. I rewired a few light switches and found that the only thing stopping a live wire touching the metal face plate was insulation tape (old, glue failing).

240v cables are joined with simple connector blocks and just left open. Paint one and you could fry.

Showers are rarely earthed because it costs money.

And when you say re-setting the breaker over and over again is a bad habit... Well, at least you have breakers and micro switches.

Still, who wants to die of old age.


wilderness profile image

wilderness 4 years ago from Boise, Idaho Author

I felt the same way on a visit to Mexico - dozens or hundreds of wires ran up the power poles and clipped to transmission lines. No protection at all, and often dangling within reach of pedestrians.

We may complain at the cost of some safety regulations and materials, but it sure pays in the long run. What third world countries do with their electricity hookups is truly scary.


alahiker28 profile image

alahiker28 4 years ago from the Deep South

Good hub. Voted up. I wonder what the importance of a ground wire is. I was recently told my home didn't have one, so I had one installed. A week later I'm quite sure my antennae was struck by lightning, but no fire. Was it my ground wire that saved me?


wilderness profile image

wilderness 4 years ago from Boise, Idaho Author

Without going into great detail, a ground system in a house does two things: it provides a path for energy to reach the earth (or the generating station) without going through your body and it provides a path for partial short circuits to enable tripping a breaker rather than building to point something gets so hot it catches fire.

If your antennae was actually struck by lightning, the ground system provided a path for that current to reach the earth without going through all the wires and electrical appliances in your house; a very good thing indeed as those wires cannot carry the current of a lightning bolt without overheating very badly. Your new ground wire could be why you still have a home.


iguidenetwork profile image

iguidenetwork 4 years ago from Austin, TX

Very informative and helpful hub. Voted up and useful. Thanks, wilderness! :)


vibesites profile image

vibesites 4 years ago from United States

Voted up and useful. This would be a life-saver! Thanks for sharing. :)


bubuwit 2 years ago

Can a very, very hot ceiling fry or make

electrical wiring sitting there to overheat?

Thanks.


wilderness profile image

wilderness 2 years ago from Boise, Idaho Author

Highly unlikely that a hot ceiling (attic) could make electrical wires overheat. At most, it will be a contributing factor, but most wiring today is rated for 90 degrees C, or 194 degrees F - that's nearly boiling temperatures. The circuit would have to already be overloaded or in some way defective for attic temperatures to fry it.


shelia 2 months ago

Loose outlets. Can it cause a fire. Lights flickering on and off. Appliances going on and off?


wilderness profile image

wilderness 8 weeks ago from Boise, Idaho Author

Absolutely it can, Shelia. Outlets wear out and a major culprit is the little springs that hold a plug into them. When that happens the electrical resistance rises, the outlet gets hot and a fire can result.

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