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

Thread Starter

Vindhyachal Takniki

Joined Nov 3, 2014
482
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.
 

crutschow

Joined Mar 14, 2008
24,081
Suppose there was a short to ground.
If the fuse is in the neutral line, it wouldn't stop the short current.
 
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Lestraveled

Joined May 19, 2014
1,946
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.
 
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boatsman

Joined Jan 17, 2008
186
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.
 

ErnieM

Joined Apr 24, 2011
8,011
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.
 

Kermit2

Joined Feb 5, 2010
4,163
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
:)
 

crutschow

Joined Mar 14, 2008
24,081
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.
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?
 

kubeek

Joined Sep 20, 2005
5,657
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.
 
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