Extension cords can overheat and cause fires when used improperly. Overheating is usually caused by overloading or connecting appliances that consume more watts than the cord can handle. Damaged extension cords can also cause fires.
However, there are potential dangers associated with leaving extension cords plugged in, such as fire hazards, shocks, and trip and fall hazards. So it's always best to unplug them when they're not in use.
Don't Run Electrical Cords Under Rugs or Through the Doorway. Avoid running the extension cord through the ceiling, walls, doorways, or under carpets. Excessive heat in such surfaces may cause the cord to overheat.
Extension Cord Fires can be Deadly
An extension cord that becomes overheated can start a fire that can end in property damage or injuries, possibly even the death of those inside the property. In 2015, an extension cord started a fire that burned the home of a family living in Brooklyn, New York.
One of the major problems with extension cords is that they're subject to everyday wear and tear. People rountinely trip over them, yanking the plug from the socket, and causing damage to the plug. Damage also occurs by doors closing on the cord or people walking over them, as well.
An electrical fire smell is often described as a “burning plastic” smell. This is because when wires overheat, the insulation surrounding them begins to break down and release chemicals into the air. These chemicals can have a strong, acrid smell that can be difficult to ignore.
The maximum length of an extension cord is set at 100-feet by OSHA standards. Any worksite that needs a longer extension must put a temporary power distribution box in place.
Hot temperatures often cause the cables to overheat. In particular, they increase the resistance of the cable conductors by forcing them to expand, making the flow of current through it more difficult, making the electrical cable less effective up to the point of it stopping working.
Using an extension cord with too small a gauge of wire for the current draw will cause the wire and cord to heat up! This can lead to melting of receptacles, damage to your electrical device (and could potentially cause an electrical fire).
Larger appliances, such as microwaves and refrigerators, may not be plugged into a power strip or extension cord. Such appliances must be plugged directly into a properly installed outlet.
One of the most common signs of damage in an extension cord is physical wear and tear. Check the entire length of the cord, including the plugs and sockets, for any visible signs of damage, such as cracks, cuts, or frayed edges. If you find any damage, stop using the cord immediately and replace it.
The green wire is the ground wire, the white wire is the neutral wire, and the black wire is the hot wire. Light-duty interior extension cords often lack the ground wire, but if a ground wire is present, be sure to connect it.
Extension cords, when improperly used, will fail. Small extension cords are appropriate for lights or alarm clocks but not appliances or power tools. Length also is important. Long cords that are undersized lose power and overheat.
Unplugging – Regardless of whether or not it's being used, as long as a power extension cord is plugged into an outlet, it's conducting electricity. To avoid potential safety hazards, always remember to unplug extension cords when they're not in use.
If you plug two identical cords into each other, that reduces their current capacity in half and can possibly result in voltage drop and overheating. In general, extension cords should not exceed 100 feet in length. However, by plugging one extension cord into another, the maximum cord length can be easily exceeded.
According to the NFPA, extension cords account for more than 3300 home fires per year. 1. NEVER use an extension cord or a power strip with portable heaters or fans.
And 99% of the time, the cord feels normal to the touch—the same as it does when not plugged in. So if you touch a plug or cord in an outlet that feels warm or hot, there's likely a problem.
Loose Plug Fuse Clips
With appliances such as hot tubs, garden heaters and electric vehicles which draw a relatively high current, the clips holding the fuse inside plug can become warm. The loose connection generates heat, the heat increases the resistance of the connection, which in turn generates even more heat.
The melting point of copper wire varies depending on the type and shape of the wire. Generally, it ranges from 1,085°C (1,985°F) to 1,215°C (2,219°F).
The temperature that wire insulation will melt depends on a multitude of factors, the greatest being the type of material. For example, PVC, a common wire insulator can melt in the range of 100-260°C (212-500°F) depending on the makeup of the PVC.
Class 1E cable is usually rated at 90ºC (if not higher). But be careful. There are some limitations here that you need to be aware of.
Don't run extension cords under rugs or furniture. Never tape extension cords to floors or attach them to surfaces with staples or nails. Don't bend or coil cords when they're in use. Cover unused cord receptacles with childproof covers.
More About Resistance
The longer you use the cord, the more heat your wire will produce. Suppose you throw a long extension through the yard or underneath the rug. In that case, the cord can get hot enough to set alight. The possibility of this occurring escalates if the cord has any damage in its length.
The OSHA regulations and National Electric Code related to these devices is as follows: Extension cords are to be used for only temporary wiring for up to 90 days. An extension cord can be used when it is running directly from the appliance to the wall, but only as temporary wiring.