Electric Extension Cord Safety Tips




Today’s electrical extension cords provide fast and convenient ways of extending electrical service throughout the home, garage, basement, and outdoors.  They allow you to power leaf blowers, weed whackers, and electric lawn mowers outdoors.  They provide instant electricity anywhere you need it inside your home; particularly in older houses that feature few wall outlets (often only one or two receptacles per room).  With today’s proliferation of electricity-thirsty mobile and desktop devices, the supply of outlets in older homes and newer homes alike, can be quickly exhausted.  Given that, the multi-outlet extension cord can really save the day, as relying on these to deliver power is much cheaper than hiring an electrician to install more outlets around the house.

However, when used improperly, extension cords can create numerous safety hazards.  Improperly placed power cables can be tripped over, causing severe injury.  They can be damaged by foot traffic or by rolling heavy carts and vehicles over them, causing short circuits, and creating potential electrical shock hazards.  They can decompose over time, posing slowly but definitely growing risks to health and welfare of those nearby.  The metal prongs on their plugs can corrode, creating high resistance connections, and the associated overheating and melting of plug and outlet components.

But like most any tool, extension cords can operate safely for many years.   Indeed, we’ve never experienced any fires, shocks, or falling due to tripping over misplaced power cables.  Simple procedures can virtually guarantee low-risk operation.  So people should not be afraid of applying extension cords

  • Buy only UL, ETL, or CSA approved extension cords.  This virtually guarantees that the extension cord meets or exceeds minimum safety standards, as established via bitter experiences over the past century.  While an Underwriters Laboratories (UL) compliant cord  is better constructed to withstand the rigors of everyday home use, the UL seal does not mean that the cord will be safe in all circumstances.  It just assures that you’re starting off with a decent and safe cable if you follow its instructions for safe use.
  • Use them for temporary applications only.  Holiday lighting, house cleaning, and yard work applications are ideal reasons for using extension cords.  They’re short-lived.  Having to lay out the cords for those Christmas decorations, or drag them to the yard for your bi-weekly weed whacking, gives you a chance to inspect the cords prior to each use, and replace any found to be defective.  However, for a permanent application, such as feeding a microwave oven or a television on the opposite side of the room as the wall outlet, the cord can become damaged, frayed, corroded, or burnt without the user ever realizing it, since we typically do not often check cords that are run behind couches, dressers, and love seats for deterioration frequently.
  • Do not overload extension cords.  Many smaller cords, intended for use on lamps, radios, clocks, and other small appliances, can quickly become overheated and pose fire hazards. Also, check that you’re not exceeding its total power handling capabilities.  The sum of all the maximum power values of the devices you’re attaching to it, should not exceed its rated maximum power handling specification. If it does, the cord will likely overheat, and could cause burns or start fires.  Plus, this situation will probably not trip the circuit breaker; especially if the cord’s rating is lower than the breaker rating.  This often occurs with thinner extension cords, that feature a maximum current rating of 8, 10, or 12 amps, while the branch circuits into which they’re typically connected are 15 or 20 amps.  The cord here will likely overheat if the sum of the currents of all the devices you plug into it exceeds its rating. Yet no problem situation will be detected at the main breaker box, if that sum is still lower than the breaker rating.  So, if you must use extension cords, employ one that handles at least the same amount of current as the hosting household branch circuit.
  • Three outlets does not mean you can safely operate three appliances.  Many multi plug extension cords feature three outlets, that convert one input outlet (the wall socket) into three outlets at the other end.  However, it’s not always safe to fill all three outlets; particularly if doing so would exceed the maximum current rating of the cord. Now it is indeed safe, if the total load current of the three appliances does not top the maximum allowable current rating.  However, if, for example, the three appliances you plug in draw 18 amps, but your extension cord is only rated to safely carry 12 amps, then you’re overloading the cord and could be creating a fire danger.  On the other hand, you can utilize all three outlets, for lower current devices.  Three radios or bedroom lamps for example, will not overheat the cord.  For this reason, we recommend that you only plug one high current appliance into any extension cord, even if that extension features three outlets.
  • Avoid repeated flexing and bending.  Frequently bending or vibrating the cable can damage the wire strands inside, lowering the cord’s safe-handling current amount.  Keep it away from doorways where it could be slammed in the door or frequently stepped on.
  • Do not route around sharp corners.  If the corner is really sharp, such as around some table legs, pulling the cord can nick or cut it.  Straight cord runs are safest therefore.
  • Avoid using in extremely hot or cold locations.  When you run an extension cord out in very cold weather, its insulation can become so stiff that it cracks when you flex it.  Or, if used in extremely hot locations, such as in attics during sunny summer days, it can grow so soft that it becomes susceptible to separation from the conductor wires.  In either case, short circuits or electrical shocks can result.
  • Avoid high traffic locations.  If you must use an extension cord, make sure you route it well away from heavily walked areas in your home.  Avoid doorways, underneath carpets, and sunny spots.  Avoid routing across the center of a room; only run along walls.
  • Do not run an extension cord in place of permanent wiring.  Extension cords should not be routed inside or through walls and ceilings, under floors, or anywhere that will complicates periodic inspection of it.  The temperature ratings of permanent wiring along with other safety factors that extension cord cable does not have, make in-wall extension cable deployment quite dangerous.  Do not do it.
  • Avoid wet locations.  While the insulation on most cords these days is initially waterproof, you can’t count on it to stay that way, unless the cord itself has been designated as waterproof or water resistant.  Extension cords designated safe for use in wet locations typically include a GFIC breaker near the plug end, which helps minimalize the effects of the sorts of electrical shocks likely to occur in damp or sopping wet places.  They also feature rubberized insulating boots around their sockets and plugs.  Most run-of-the-mill cables however, do not have these safety features, and unless your extension cord does, then for your own safety, please do not run it in or near water.  Even the safest rated cords should not be routed through standing or flowing water.
  • No nailing or stapling of cords in place.  Careless stapling can puncture cable insulation, creating short circuits and shock hazards.  Further, over time, the cable can expand, contract, or otherwise shift position.  When stapled, such shifts can erode the insulation, especially when the cable was initially tightly clamped in place, and create electrical failures and hazards, years after installation.
  • Inspect extension cord parts often.  Look over the cable, checking for tears, nicks, cuts, and frays.  Replace any extension cords showing these symptoms.  Also, examine all connecting prongs.  For safest maximum current handling capability, all prongs should gleam and shine brightly.  Dull or corroded prongs could create a hot connection due to the additional resistance to current flow that corroded or otherwise dirty connections can create.  Repair any bare wires with high-grade electrical tape.
  • Fully insert all plugs.  You don’t get the rated maximum safe current handling capability of an extension cord, unless you fully insert, all the way, its plug into the wall outlet, and the appliance plug into the extension cord’s socket.  Partially inserted plugs, where you can still see the prongs are dangerous for at least two reasons.  First, the can be more easily touched, elevating the shock hazard.  Second, with less than the full surface areas of the prongs and sockets in direct contact with each other, the connection can become hot, and this heat can damage the surrounding insulating materials in the extension cord as well as the wall outlet into which it is plugged.  So, keep all plugs completely plugged in.
  • Verify no overheating.  Any time you change the appliances the cord powers, or at least once per month, check the extension cord for excessive warmth.  Symptoms of overcurrent heating include softening of the insulating plastic or rubber around plugs and sockets, discoloration of any part of the cord, and a “hot” rubbery smell when the cord is in use.  Such heating typically occurs at each end of the extension cord, though hot spots can occur anywhere along the cable.  So run your fingers through the entire cord, looking for these hot spots.  If the entire cord is excessively warm, replace with a higher capacity model.
  • Use extension cords with built in circuit breaker.  To reduce the chances of overloading the extension cord, buy only models that feature a built-in current limiting circuit breakers.  Often found in extension cords designed for outdoor use, cord-bound circuit breakers are part of the GFCI breaker switch.  Not only does the GFIC breaker guard against ground faults, but also trips out if the extension cord’s maximum current rating is exceeded.
  • For outdoor use, plug into only GFCI outlet.  For all outdoor applications, plug all extension cords into GFCI protected outlets only.  Better yet, use only exterior extension cords that feature built-in GFCI breakers.  Or, if you can’t afford to replace your existing extension cords with GFCI models, you can purchase a GFCI adapter box.  You plug your cord into this box, then plug this GFCI box into an outlet.  The box adds GFCI protection to any extension cord plugged into it.
  • Keep all electrical connections dry.  Do not expose them to water or other chemicals, unless for the express purpose of cleaning and de-corroding them.   Repeated exposure to dampness and wetness can corrode the connecting prongs (particularly on brass plugs and sockets), and degrade the extension cord’s performance and safety ratings.
  • Run minimum length required to do the job.  The longer the cord the higher its resistance, and the less power it will deliver to load devices.  Keeping the cord as short as possible not only maximizes appliance performance (especially in high current draw appliances such as hair dryers), but less cable means less entanglement hazard.
  • Avoid coiling long extension cords to shorten them.  Keep them straightened out.  The coiled wire itself can act as an inductor; causing excessively lowered voltage at the powered appliance, which in turn can trigger faulty operation of that appliance, as well as potential damage to it.  The coil itself can overheat, causing insulation failure and fire.  Again, use the shortest extension cord you can.
  • Avoid daisy-chaining extension cords.  The more cords you connect end-to-end, even the heavy duty ones, the more potential points of failure, since the link can be disrupted in more places, by someone snagging their foot on the cable.  Plus, each socket-to-plug connection introduces more total resistance into the link, which potentially can degrade performance in high-current appliances.  Most extension are designed to be used one-at-a-time, and not hooked in series.  So, do use them that way.
  • Block off any unused extension cord sockets.  Single outlet covers cost little, yet prevent young children from inserting objects into socket holes and potentially and fatally shocking themselves.  Therefore, we recommend stopping up all open extension cord outlets.
  • Do not use indoor extension cords outdoors.  Indoor cords tend to be more widely available, less water resistant, less sun resistant, less rugged, and lighter duty than outdoor ones. On the other hand, outdoor extension cords, though more expensive, can typically tolerate more twisting, crushing, and bending, without failing or becoming hazardous.  Their jackets are UV stabilized so that they do not harden or grow brittle while baking in long hours of sunlight.  Finally, outdoor cables are typically more brightly colored (except for the ones intended for garden lighting).  So they pose less of a tripping danger.

 

Society couldn’t get along without the millions of extension cords out there these days in bedrooms, living rooms, offices, auto repair shops, and concert stages.  They offer power where and when you need it, can be quickly set up and removed, and cost little.  Thus, their advantages far outweigh their potentially dangerous drawbacks.  Yet even their downsides can be virtually eliminated by learning how to select and deploy them.  We hope this article helps educate you about how to use extensions in the safest ways, and to take best yet safest advantage of them.

 

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Revision History

  • 2017-01-28: Updated tags list.  Changed post title to: Electric Extension Cord Safety Tips.
  • 2015-10-17: Added appropriate tags.
  • 2015-09-19: Added discussion about indoor Vs. outdoor extension cords.
  • 2015-09-14: Originally published.