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Thread: Please Explain Small Gauges of Extension Cords

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    DIY Senior Member molo's Avatar
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    Default Please Explain Small Gauges of Extension Cords

    I know that a general rule is to not reduce the size of wire, so then why are extension cord sizes for appliances so small? Are they sized to the appliances demand?

    Thanks in Advance
    "Any American who is prepared to run for President should automatically, by definition, be disqualified from ever doing so."
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    Electrical Contractor/Instructor jwelectric's Avatar
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    Are you talking about the supply cord that comes on an appliance or are you talking about the cord that has a male and female end cap? Table 400.5(A)(1) gives the ampacity of cords

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    Plumber jimbo's Avatar
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    Ampacity is always a concern. And especially when you say "appliance". Small 16 or 18 gauge general purpose extension cords are intended for a lamp, a TV, etc etc. and lengths are limited....6 to 12 feet usually. When you are talking about a device which is rated at 12 to 15 amps......refrigerator, air conditioner, microwave, etc. while a light duty cord may be "rated" for that, continous use will tend to overheat the cord, and especially the end fittings which are applied with light duty crimp manufacturing techniques. For such applications, you should get a cord rated for appliances, "heavy duty" , 12 amps, etc. And EVEN THOSE, I happen to use them for my 1500 watt oil filled portable radiators. I always cut off the manufactures end fittings, and replace with "heavy duty" cord ends. This always eliminates the "hot plug" which you experience on the factory ends.

    In terms of your question about wire size......the answer is distance ( length). For example, our 'rule of thumb' is 14 gauge wire in the wall for a 15 amp circuit. But that is based on the very long total length of wire in the wall. It IS ok to reduce to say 16 gauge for 6' on an extension cord. That gauge will carry the current without overheating the wires.
    Last edited by jimbo; 11-08-2012 at 05:40 AM.

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    Moderator & Master Plumber hj's Avatar
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    You buy the extension cord based on the length of the cord and the load you are going to plug into it. Often, the very lightest cords have a polarized two slot configuration which will not accept the plugs for the "heavier" devices which have a three prong plug.
    Licensed residential and commercial plumber

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    DIYer, not in the trades LLigetfa's Avatar
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    The maker and the seller does not know what sort of appliance you will plug into an extension cord. They make different gauges in different lengths for a variety or uses. It is up to the buyer to know what to get but the buyers all too often use price as their main deciding factor. Makers and sellers know that and tend to make and stock more of the smaller gauge cords.

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    DIY Senior Member molo's Avatar
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    I am referring to things like space heaters. I had a 1,500 watt space heater plugged in yesterday and the plug and cord were getting quite warm!
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    DIYer, not in the trades LLigetfa's Avatar
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    So then this is the permanently attached appliance cord, not an extension cord? Why then are we talking about extension cords?

    If you had it plugged into a cheap extension cord, that could explain it.

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    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by molo View Post
    I am referring to things like space heaters. I had a 1,500 watt space heater plugged in yesterday and the plug and cord were getting quite warm!
    1500/120= 12.5 Now add the 125% as mandated in 424 and we have 15.65 amps of current flowing through that cheap cord cap.

    In every class I teach I point out that a 1500 watt electric heater is a violation when plugged into a 15 amp general purpose receptacle, see 210.21 through 210.23 for more information.

    These heaters are a fire waiting to happen. If you must use one make sure that it is plugged into a 20 amp circuit and this will relieve the heat in the cord to some extent but I will not eliminate it altogether.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Basically, an attached cord to an appliance should work okay when plugged into a receptacle designed for the load. When adding an extension to the cord, that's where it gets critical to maintain at least the wire size of what is on the device, and better yet, use a heavier gauge one to account for the connections at either end. Also, an old, worn out extension cord should either be chucked or the end(s) replaced when things get loose. To get an approval, the cord that comes with it should be sufficient for the load of the device.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Electrical Contractor/Instructor jwelectric's Avatar
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    The major problem is someone will go to Walmart and get a portable electric heater that is rated at 1500 watts but runs all the time as the thermostat on the unit never satisfies and the load if far to great for the 15 amp receptacle that it is plugged into. The receptacle slots start to heat and expand and then the heat is transferred to the blades of the male plug on the end of the cord.

    At some point the cord caps get so lose in the slots of the receptacle that we spread the blades of the male plug to make it grip tighter until the male plug starts to deform.

    Table 210.21(B)(2) tells us that the maximum cord connect load that can be plugged into a 15 amp receptacle is 12 amps. It doesn’t matter if the 15 amp receptacle is on a 15 or 20 amp circuit the largest cord connected load that can be plugged in is 12 times 120 or 1440 watts.

    There is two times that a circuit is to be rated at 125%.when talking about this type of a load. One is when the load is going to last for three hours or more and the second is found in 424 concerning electrical resistive heating elements.

    In most cases these heaters are set on high and never reach the temperature to satisfy the thermostat and run for several hours on end. There is no break to allow things to cool down and the heat keeps intensifying until something bad happens.

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    Plumber jimbo's Avatar
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    As to the space heater.....not surprised it caused the ends to heat up. Those are the weak points on small cords. Get a heavy duty cord rated as "appliance" or such, 14 ga min, 12 ga preferred. And then, REPLACE the end fittings as I pointed out before. I have been using portable heaters for years, using this procedure. I keep the extension cord length to 4~6 feet max. BTW I also replace the mfg installed plug on the heater with a heavy duty version.

    As pointed out, heaters have inherent potential dangers, but you can minimize. Rule #1....you don't SLEEP with a heater turned on!

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    DIY Senior Member molo's Avatar
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    I should clarify that I was referring to appliance cords not extension cords. I would be willing to bet that only 1 in 1,000 know that a 1,500 watt heater should not be plugged into a 15 amp circuit. If properly designed an electric space heater wouldn't be a hazard (there are probably some out there that are OK).
    "Any American who is prepared to run for President should automatically, by definition, be disqualified from ever doing so."
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    Plumber jimbo's Avatar
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    Quote Originally Posted by molo View Post
    I should clarify that I was referring to appliance cords not extension cords. I would be willing to bet that only 1 in 1,000 know that a 1,500 watt heater should not be plugged into a 15 amp circuit. If properly designed an electric space heater wouldn't be a hazard (there are probably some out there that are OK).
    Most small room heaters are rated at 1500 watts, and the also all have a plug allowing use on a 15 amp receptacle.

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    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by jimbo View Post
    Most small room heaters are rated at 1500 watts, and the also all have a plug allowing use on a 15 amp receptacle.
    This is true and there would be no problem if they came on for a few minutes and then shut off like you furnace but this heater is being used in NY where there is no power and it is running 24/7 which it was not designed to do therefore it does not hold up.

    They are not designed to heat a house. They are designed to be foot warmers and the time of operation is not continuous.

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    Plumber jimbo's Avatar
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    Quote Originally Posted by jwelectric View Post
    This is true and there would be no problem if they came on for a few minutes and then shut off like you furnace but this heater is being used in NY where there is no power and it is running 24/7 which it was not designed to do therefore it does not hold up.

    They are not designed to heat a house. They are designed to be foot warmers and the time of operation is not continuous.
    I believe that fire departments around the country would concur with your analysis. This whole thing is just one of those loopholes that allow Darwin's Laws to come into play!!!!

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