Extension leads (extension cords) are widely used in homes, offices, and construction sites to power electrical devices where fixed sockets are not available. While they are convenient and practical, they can become dangerous if used incorrectly. One of the most common and overlooked hazards is using an extension lead while it is still coiled or wound on a reel. A coiled extension lead can overheat quickly and may cause a fire, especially when connected to high-power appliances.
Understanding why coiled extension leads are dangerous and how fires can occur is essential for preventing accidents and protecting property and lives.
What Is a Coiled Extension Lead?
A coiled extension lead fire is an electrical cable that remains wound in loops, usually on a cable reel or wrapped in a circular shape. Many extension cords are sold on reels so they can be easily stored and transported. However, problems arise when the cable is used without fully unwinding it.
When electricity flows through a cable, it naturally produces heat. If the cable is tightly coiled, the heat cannot escape easily. As a result, the temperature of the cable increases rapidly, which can melt insulation and potentially start a fire.
How Coiled Extension Leads Cause Fires
There are several ways a coiled extension lead can lead to a fire hazard. These include heat buildup, insulation damage, and overloading.
1. Heat Buildup
Electric current passing through a wire produces heat due to electrical resistance. Normally, this heat dissipates into the surrounding air. However, when the cable is coiled, the heat becomes trapped between the loops of wire.
Each loop warms the next one, creating a cumulative heating effect. Over time, the temperature can rise high enough to damage the cable insulation.
2. Insulation Melting
Extension leads are covered with plastic or rubber insulation designed to protect the internal wires. When excessive heat builds up, this insulation can soften or melt.
Once insulation melts:
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Wires may become exposed
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Short circuits can occur
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Sparks may be produced
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Fire risk increases
3. Overloading the Cable
Many people connect high-power appliances to extension leads without checking their ratings. Devices such as heaters, irons, microwaves, and electric kettles draw large amounts of current.
If a coiled extension lead is overloaded:
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Current increases
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Heat increases
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Fire risk increases dramatically
The Science Behind Cable Heating
When electricity flows through a conductor, resistance converts some electrical energy into heat. This is known as Joule heating. The amount of heat produced depends on:
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Current flowing through the cable
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Length of the cable
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Thickness of the wire
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Quality of insulation
A coiled cable acts like a heat trap. Since air cannot circulate freely between the loops, the heat stays concentrated in one place.
In extreme cases, the cable temperature can exceed safe limits within minutes.
Common Situations Where Fires Occur
Coiled extension lead fires often occur in everyday situations, such as:
Home Use
Many households use extension reels for:
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Heaters
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Air conditioners
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Washing machines
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Irons
Using these devices with a coiled cable is especially dangerous.
Construction Sites
Construction workers often use extension reels for:
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Power tools
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Drills
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Welding machines
Heavy equipment draws significant power, increasing the risk of overheating.
Offices
In offices, extension leads power:
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Computers
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Printers
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Heaters
Even moderate loads can cause overheating if the cable remains coiled.
Warning Signs of an Overheating Extension Lead
Recognizing the warning signs of overheating can help prevent fires.
Common signs include:
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Cable feels warm or hot
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Burning smell
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Soft or melted insulation
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Discoloration of the cable
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Sparks near plugs
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Circuit breaker trips frequently
If any of these signs appear, the extension lead should be unplugged immediately.
Fire Risks and Consequences
A coiled extension lead fire can spread quickly and cause serious damage.
Property Damage
Fires can destroy:
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Furniture
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Walls
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Appliances
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Wiring
Electrical Damage
Electrical fires often damage:
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Sockets
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Switchboards
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Circuit breakers
Injury Risks
People may suffer:
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Burns
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Smoke inhalation
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Electric shock
According to safety guidelines from organizations like the National Fire Protection Association, electrical equipment is one of the leading causes of house fires worldwide.
Why Extension Reels Have Ratings
Most extension reels have a label indicating maximum power ratings. These ratings often differ depending on whether the cable is coiled or fully unwound.
For example:
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Fully unwound: 3000 watts
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Coiled: 1000 watts
This difference exists because a coiled cable cannot safely dissipate heat.
Ignoring these ratings increases the risk of fire.
Preventing Coiled Extension Lead Fires
Preventing extension lead fires is simple if proper precautions are followed.
1. Fully Unwind the Cable
Always unwind the extension lead completely before use, especially when powering high-wattage devices.
This allows heat to escape and keeps the cable cool.
2. Avoid Overloading
Check the power rating of the extension lead and ensure connected devices do not exceed it.
You can calculate power using:
Power (Watts) = Voltage × Current
3. Use Quality Extension Leads
Cheap or low-quality cables may not handle heat properly.
Choose extension leads with:
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Thick insulation
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Proper certification
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Clear ratings
4. Keep Away from Flammable Materials
Do not place extension leads near:
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Curtains
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Carpets
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Paper
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Wood
These materials can catch fire easily if the cable overheats.
5. Inspect Regularly
Check extension leads for:
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Cracks
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Cuts
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Melt marks
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Loose plugs
Damaged cables should be replaced immediately.
Safe Usage Tips
Here are some general safety tips:
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Never run extension leads under carpets
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Avoid using damaged cords
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Do not connect multiple extension leads together
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Keep cords dry
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Unplug when not in use
These simple steps can significantly reduce fire risk.
Extension Leads vs Permanent Wiring
Extension leads are meant for temporary use. Permanent wiring is safer for long-term electrical needs.
If you frequently need extension leads, consider installing additional wall sockets. This reduces reliance on extension cords and lowers fire risk.
Importance of Fire Awareness
Many extension lead fires occur because people are unaware of the risks. Education and awareness are key to prevention.
Simple actions like fully unwinding a cable and checking ratings can prevent serious accidents.
Electrical safety should always be a priority in homes and workplaces.
Conclusion
Coiled extension lead fire pose a significant fire hazard due to heat buildup and poor ventilation. When cables remain coiled, heat becomes trapped between the loops, causing insulation to melt and increasing the risk of electrical fires.
High-power appliances make the situation even more dangerous, as they draw more current and produce more heat. Overloading a coiled extension lead can quickly lead to overheating and potentially start a fire.
Fortunately, these risks can be easily prevented by fully unwinding cables, avoiding overload, and regularly inspecting extension leads for damage. By following basic electrical safety practices, the risk of extension lead fires can be greatly reduced.
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