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Electrical Plugs Should be Plugged In All The Way

January 27, 2012

Today’s picture is an appliance and extension cord and it underscores a common problem with electrical connections.

Ohm’s law specifies the relationship between voltage, amperage and resistance.  Electricians and engineers pay careful attention to this law and how things are designed and wired.  One concern is the amount of cross-sectional area you have in your conductor (wiring) which determines how much current the conductor can safely handle.  The more cross-sectional area to your conductor (the thicker the wire size) the more current it can safely handle.  If you reduce the cross-sectional area (thinner wire size) but still try to push the same amount of current through, you generate heat.  Reduce the cross-sectional area enough and you can generate enough heat to ignite nearby combustibles.  That’s why we want you to ensure your extension cord is big enough to handle the amperage load put on it (see “Extension Cord Safety” on this blog or http://wp.me/p1jTZ6-67).

One thing that reduces cross-sectional area is poor electrical contacts.  If electricians do not install outlets and switches correctly, poor contacts create heat and switches and outlets can melt down or ignite.  If the consumer does not ensure that plugs are plugged all the way in, there is less contact, which reduces cross-sectional area of the contact, and heat is again generated.  The technical term is ‘high resistance heating’.  Fire investigators often refer to this as a ‘glowing connection’ and frequently evaluate electrical connections in determining fire cause.

In our picture here, the appliance was a 1500-watt heater (12.5 amps).  The extension cord was rated to 1650 watts (13.75 amps).  The cord was plenty big enough for this heater.  The problem was that the consumer did not push the heater cord plug all the way into the extension cord receptacle.  This reduced the amount of contact between the plug and receptacle.  The heater still demanded the full 1500 watts (12.5 amps) and the poor connection overheated, melting the plug and receptacle as well as the carpet beneath.  This connection was pushed beneath the sofa and was out of sight.  A very conscientious homeowner went round checking extension cords and found this BEFORE it caught fire.  That’s how we got hold if it.  Normally we find things like this at the bottom of a pile of burnt debris after a structure fire.

Electrical plugs MUST be pushed all the way into receptacles in wall sockets as well as extension cords.  Failure to do so could result in a fire at your house.  If your household receptacles are loose and don’t hold plugs tightly (plugs sag or fall out), have them replaced.  The cheapest receptacles at the local hardware store may save you money, but they’ll wear out quicker.  Paying a bit more money for higher quality electrical receptacles will ensure your appliances will have the best contact and reduce your chance of a fire.

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From → Fire Prevention

2 Comments
  1. What a great article! I have a friend who is an electrician, who just gave me some valuable information on electrical plugs. When you have to pry open the metal part of a cord that you are going to plug into an electrical outlet to make it fit…the problem is not the “prongs” that you are plugging in..it is the outlet. Who knew??? I have been prying these prongs in and out to make it stay in the outlet for more years than I want to remember. Now I find out that this is a huge fire hazard. Hopefully this information will help others and prevent an elkectrical fire.

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