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  1. #1
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    Default Why do receptacles have a different hot and neutral side?

    I found out yesterday that the receptacle to our washing machine was reversed.....the hot and neutral wires were switched. I changed them around.

    That left me wondering why there is a distinction on modern receptacles between the hot side (the narrow opening) and the neutral side (the wide opening) ....any answers?

  2. #2
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    Default Re: Why do receptacles have a different hot and neutral side?

    The way an electrician essplain'd to me once, (he was actually explaining the reasoning behind "polarized" plugs ) is say you have a light socket. Normally, the hot comes to the dot in the bottom of the socket, the threaded well is the neutral. With it in this configuration, should you touch the threaded well you won't get shocked. If you switch the configuration, the well becomes energized and the real possibility of shock or electrocution exists when changing the bulb or handling the fixture.

    It stands to reason that outlets and other appliances behave similarly, so the need for a properly wired outlet is necessary. And outlets have been color coded with brass screws on the hot side and silver screws on the neutral side for as long as I can remember. The easiest way to remember which side is which is that the neutral and ground screws will always be on the same side of the outlet.
    I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!

  3. #3
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    Default Re: Why do receptacles have a different hot and neutral side?

    Another reason why you NEVER use a CFL in a lamp with a non-polarized plug.

  4. #4
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    Default Re: Why do receptacles have a different hot and neutral side?

    Thanks for the answers.....I thought it was too basic a question for this forum, but now I'm glad I asked!!

    I found a very definitive answer on the web, again from Wikipedia (http://en.wikipedia.org/wiki/Polarized_plug):

    "Polarised plugs and sockets are used for safety reasons. Polarised connectors are used to maintain the identity of the neutral conductor in the connected equipment. This is important so that switches, for example, interrupt only the live wire of the circuit. Polarisation is maintained by the shape, size, or position of plug pins and socket holes to ensure that a plug fits only one way into a socket.

    If the neutral wire were interrupted instead, although the device would deactivate (due to the opening of the electrical circuit), its internal wiring would still be energised. This can present a shock hazard if the device is opened, because the human body would create a circuit a path to a voltage different from that of the live wire. Interchange of the hot and neutral wires in the behind-the-walls household wiring can thus create a safety hazard."


    So...this raises some further questions:

    1- I would not be surprised if several threaded lamp sockets are wired backwards in this old house, with the hot to the socket walls and the neutral to the lamp base. Is there any way of easily testing a socket to see if it is wired correctly, without taking it apart??

    2- Why can't you use a CFL bulb in a fixture with a non-polarized socket? What would happen??

    Anybody know??

  5. #5
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    Default Re: Why do receptacles have a different hot and neutral side?

    Run a wire from a good ground and hook it to one of the leads from a volt meter, remove the bulb and turn the light switch on, touch the other lead to the center button in the socket then to the metal threaded side. If the button reads hot you're OK, if the threaded side reads hot the wires are reversed.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  6. #6
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    Default Re: Why do receptacles have a different hot and neutral side?

    Quote Originally Posted by rickpantel View Post
    :

    1- I would not be surprised if several threaded lamp sockets are wired backwards in this old house, with the hot to the socket walls and the neutral to the lamp base. Is there any way of easily testing a socket to see if it is wired correctly, without taking it apart??

    2- Why can't you use a CFL bulb in a fixture with a non-polarized socket? What would happen??

    Anybody know??
    When the plug is inserted backwards (shell is hot) the cfl base can start afire/melt. I learned this the hard way.

  7. #7
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    Default Re: Why do receptacles have a different hot and neutral side?

    there is also a tester you can buy almost anywhere that you simply plug in and it will show you by a combination of lights if it is wired correctly.


    http://www.acmehowto.com/howto/homem...outlettest.php

  8. #8
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    Default Re: Why do receptacles have a different hot and neutral side?

    OK, OK guys...no more flames (the internet kind not the electrical kind!). Me and most of the other readers here are trying to learn something about electricity, and the bickering kind of gets in the way. Jeeeez!

    I would have thought that the manufacturers of the CFL's would take into account the possibility of a reverse wired lamp socket, and designed their light so that overheating/fire would not occur. However, if this has been observed by a contributor to this forum (note they did not say that they were the one who wired the socket incorrectly), that is good enough for me to red-flag the situation as possibly dangerous.

    I think A. Spruce's point about a reverse wired lamp socket having a hot shell and be more dangerous was an excellent point.

    Havanagranite: I've got one of those little testers and it works great in a standard plug-in receptacle, but it won't work in a lamp socket without some kludging. Maybe it is worth splicing together a little device to check if a lamp socket is wired in reverse....sort of a screw in male lamp base on one end, and a receptacle on the other where you can fit the polarity tester? Can you buy something like this?

    No more flames please....please only post if you have something positive to contribute.

  9. #9
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    Default Re: Why do receptacles have a different hot and neutral side?

    How about using a plug adapter and a 3 prong adapter and use your tester.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  10. #10
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    Default Re: Why do receptacles have a different hot and neutral side?

    Quote Originally Posted by rickpantel View Post
    I would have thought that the manufacturers of the CFL's would take into account the possibility of a reverse wired lamp socket, and designed their light so that overheating/fire would not occur. However, if this has been observed by a contributor to this forum (note they did not say that they were the one who wired the socket incorrectly), that is good enough for me to red-flag the situation as possibly dangerous.

    I think A. Spruce's point about a reverse wired lamp socket having a hot shell and be more dangerous was an excellent point.

    Havanagranite: I've got one of those little testers and it works great in a standard plug-in receptacle, but it won't work in a lamp socket without some kludging. Maybe it is worth splicing together a little device to check if a lamp socket is wired in reverse....sort of a screw in male lamp base on one end, and a receptacle on the other where you can fit the polarity tester? Can you buy something like this?
    You can do a continuity check with a ohmmeter.

    Of course with the lamp unplugged.

    One meter lead to the center "button" of the socket ..... other meter lead to the smaller metal spade .

    Meter lead on the threaded portion with the other meter lead on the larger spade.

    With these arragements there should be continuity which indicates properly wired.

    In respect to the lamp cord itself ... the one wire that is marked with letters or a rib in the cover indicates the neutral conductor.
    "" an ounce of perception -- a pound of obscure "
    - Rush

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