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Extension Cord Safety

by Hickerson Brothers on May 12, 2016

Electrical Extension Cord SafetyExtension cords are amazing.  When we need to power something and the cord is too far away from an outlet, rather than move the device, we simply find an extension cord and plug it in.  They increase the range of our plugged in devices without the cost of extensive electrical work.  Unfortunately, overuse of electrical extension cords (designed as a temporary extension for short use) can lead to dangerous fire risks.

Risks of Extension Cords

Here’s the problem, everything on an electrical circuit adds a small amount of electrical load (power usage) to the circuit.  Wires are not fully conductive, and the small amount of resistance in a length of cord converts electrical energy into heat energy.  When you add an extension cord to an electrical circuit, the overall power-loss on that circuit goes up in the form of heat produced by the cord.

Of course, a single extension cord connected to a device isn’t a problem.  But tie two cords together, plug in a power strip, or connect the cord to a high power device such as a space heater or curling iron and you’re asking for major heating issues.  Heating on an extension cord has the potential to cause two different problems: fires and circuit overloads.

There’s a strange property of electrical conductance when a material is heated.  Conductivity (how easily a material allows heat and electricity to move through it) decreases as the temperature increases.  What does this mean? Well let’s say you connect two extension cords to give yourself a few extra feet of space.  That added resistance generates heat as power moves through it.  A small amount of heat is always going to be given off, but when enough is added your circuit can enter a runaway state:

  1. Heating on a wire increases resistance
  2. Power demand for the circuit increases due to increased resistance
  3. Additional heating on the wire increases the resistance again
  4. Runaway state where power demand and resistance continue to increase uncontrollably
  5. Breaker Trip or Insulation Fire

This is the most dangerous risk of using a functional (undamaged) extension cord.  You always want to avoid heating issues when you’re using an extension of any kind.  So how do you reduce the heating of an extension cord?  Use extension cords as a temporary measure for only a single device.  If you need to power a high-load appliance (such as a power tool in the garage) make sure that you’re using an extension cord with a lower gage (the cable will be thicker).  And make sure that you have the shortest extension cord possible.  The shorter the cord, the lower the overall resistance will be.  A shorter cord will also avoid coils with can overheat the cable faster.

Safety Practices

Heating isn’t the only safety risk you’ll find when using extension cords.  These temporary measures for power solution should follow simple safety rules for every use.  Always inspect your cord for damage before use. Never use a cable with insulation damage, frayed wires, or a broken plug.  Only purchase cables that have been approved by an independent testing laboratory (UL, ETL, or SA for example).  Never treat an extension cord as a permanent solution.  As a healthy reminder, this infographic from the Electrical Safety Foundation International (ESFI), is a handy tool to help you double check how you’re using extension cords around your home and office.  Stay safe everyone!

ESFI Extension Cord Safety


Hickerson Electrical is your source for all home electrical services.  We’re ready and willing to deliver top-quality service to your home at a moment’s notice.  So call today at (703) 594-3913.

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