Why fuse always placed on line not on neutral, 2 pin plug

Discussion in 'General Electronics Chat' started by Vindhyachal Takniki, Mar 29, 2016.

  1. Vindhyachal Takniki

    Thread Starter Member

    Nov 3, 2014
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    1. I have seen some people recommended to always place to place fuse on line and not on neutral (220Vac,50Hz). I have application which has two pin plug which is plugged into main socket.

    2. I mean what difference it make whether I place it on neutral or line. Since end user can plug 2 pin plug into socket in any direction. i.e socket line can be plugged into plug netural & vice versa.

    3. Moreover why in ac line & neutral are different. Isn't we can plug our equipment in any direction & it works.
     
  2. crutschow

    Expert

    Mar 14, 2008
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    Suppose there was a short to ground.
    If the fuse is in the neutral line, it wouldn't stop the short current.
     
    Last edited: Mar 29, 2016
  3. Lestraveled

    Well-Known Member

    May 19, 2014
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    Sometimes it is hard to to see the strategy of where to place the fuse.

    Imagine this:
    Step #1 - Take a coffee maker, plug it in and lay it on its side. Take a 16 penny nail and wrap a ground wire on it. Take a big hammer and pound the nail into the the side of the coffee maker. If the fuse was on the neutral side it would not blow, because neutral and ground are the same voltage. But, because the nail is at ground and the fuse is on the hot side, the fuse will blow, preventing you from being electrocuted.

    Step #2 - buy another coffee maker.
     
    Last edited: Mar 29, 2016
  4. boatsman

    Senior Member

    Jan 17, 2008
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    If the fuse is on the neutral wire and receives a sudden high current so that it melts, the circuit will be interrupted but there will still be 220 volts in the wiring up to the fuse.
     
  5. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    Look carefully at that two pin plug you intend to use. Is one pin taller than the other pin? If so that pin in phased for a hot and neutral connection. Hot is the smaller pin, and the proper place for a fuse.

    If both pins are the same height it is intended for unphased connections where hot and neutral are free to swap. In such a case you should use two fuses, one in each line, so that there is always a fuse in the hot leg to blow.

    No I am not being a pedantic twit when I say to do this. Even el-cheapo Christmas lights strings will have two fuses when they use unphased plugs.
     
    Vindhyachal Takniki likes this.
  6. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Government type bureaucratic regulations require that makers of utility power utilizing devices add protection to their products to prevent idiots from winning a Darwin award.

    Fuse the Damn hot side and stop questioning our bureaucracy
    :)
     
  7. crutschow

    Expert

    Mar 14, 2008
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    So the only reason fuses are used is because of government bureaucracy? :confused:
    And here I though that fuses were used to keep a device from burning up in case of a part failure. o_O
    So, how does a fuse prevent one from winning the Darwin award?
     
  8. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Kermit2 forgot to use the <sarcasm> tags ;)
     
  9. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    A two pin plug implies a class II appliance that has double insulation. In that case it should not matter which of the poles you put the fuse on.
    Edit: in some countries. Somewhere else appliances could have entirely different regulations.
     
  10. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Different regulation in visual form:

    Electricans-nightmare.jpg
     
  11. MaxHeadRoom

    Expert

    Jul 18, 2013
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    That looks the average installation in India where you bung a local electrician a few Rupees to hook your extension cord up to the pole!:p
    Max.
     
  12. Marcus2012

    Member

    Feb 22, 2015
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  13. Vindhyachal Takniki

    Thread Starter Member

    Nov 3, 2014
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    I will place two fuses one in each line & neutral since plug can be reversed.
     
    ErnieM likes this.
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