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I have been doing some research on this question. The answer I get most of the time is that this is for safety reasons. That there can be no current in the neutral that didn't come from the live. If anyone has a clear answer, please tell me.

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    \$\begingroup\$ if lines are fused then how do you get any neutral current? fusing neutral would expose hot lines unprotected \$\endgroup\$ – Tony Stewart EE75 Oct 10 '16 at 18:17
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    \$\begingroup\$ Fusing neutral would expose hot lines unprotected, on an appliance that had 'stopped working'. Fusing live does not have this defect. \$\endgroup\$ – Neil_UK Oct 10 '16 at 18:22
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    \$\begingroup\$ @user104474 No need to be rude. He answered your question very clearly. If you had a fuse on the neutral and it blew, you'd still have the HOT connected to your appliance, which means it could still cause damage or electrocution. \$\endgroup\$ – DerStrom8 Oct 10 '16 at 18:23
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    \$\begingroup\$ @user104474: Chill. Nobody is supposed to do anything. A lot of people can and many will help. Mouthing off is a good way to turm them off, though. \$\endgroup\$ – JRE Oct 10 '16 at 18:23
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    \$\begingroup\$ Agreed. @user104474 with your attitude, you should be thankful that anyone is answering you at all. \$\endgroup\$ – DerStrom8 Oct 10 '16 at 18:24
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  1. Cost: One fuse in the live is adequate to cut current to the circuit.
  2. Isolation: If the neutral fuse blows first the circuit would stay live. It's generally best to disconnect the circuit from mains.
  3. Polarity: Many countries don't use polarised plug and sockets on single-phase plugs. This means that the fuse in the appliance may indeed be in the neutral. So, to answer your question, "Why is it not advisable to fuse the neutral?" - we do it all the time in many countries.

enter image description here enter image description here

Figure 1. Unpolarised American (120 V) and European (230 V) mains plugs.

Update:

Note that with the unpolarised plugs the fuse can only be guaranteed to protect against over-current in the device itself. e.g., a motor short-circuit will cause the fuse to blow. With the fuse in the neutral wire a short to earth would not cause high current to flow through the fuse.

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  • \$\begingroup\$ In countries that use non-polarized plugs, is one of the wires considered "neutral" or are they both "hot?" \$\endgroup\$ – mkeith Oct 10 '16 at 18:32
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    \$\begingroup\$ A live and neutral connection are made to the rear of the socket. You can't tell from the front which is which so you have to assume that either can be hot. \$\endgroup\$ – Transistor Oct 10 '16 at 18:35
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    \$\begingroup\$ Another reason, in the housing installation, is protective earth wiring. It may be "nulled" in old houses, meaning protective earth and ground are tied together at the outlet, not at the switchbox. If you have your switchbox fuses in the ground line, you have no protective earthing as soon the fuse blows, and worse, all appliances connected which have protective earthing have their earth still connected to ground, and through the appliance resistance (think "toaster") also to hot. \$\endgroup\$ – Janka Oct 10 '16 at 18:48
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    \$\begingroup\$ @mkeith devices to be used with symmetrical mains sources are designed assuming that BOTH sides are "hot" since there is otherwise no way of determining if one is bonded (or even closer) to ground. One popular scheme is "Double Insulated" where there is double protection between powered circuits and the user. \$\endgroup\$ – Richard Crowley Oct 10 '16 at 20:13
  • \$\begingroup\$ I guess what I am really asking is, if a country uses two current carrying conductors and non-polarized plugs, do they even bother to earth ground one of the conductors somewhere (e.g., at the service entrance to the building). \$\endgroup\$ – mkeith Oct 10 '16 at 21:46
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Having a device appear to be electrically dead while its components are electrically live can be dangerous; if the neutral were fused, an overcurrent fault could easily create that dangerous condition unless the fusing assembly ensured that an overcurrent condition would disconnect both hot and neutral simultaneously. While it's possible to construct fuse assemblies in such fashion, such assemblies are generally much more expensive than those which only disconnect the wire through which excessive current is flowing.

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Fuses are not recommended in neutral.

  1. To ensure complete isolation with the removal of fuse.
  2. To make the total current always flows through the fuse.
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If you put a fuse in the neutral and there's a short to ground the current will bypass the neutral and not blow the fuse ... things get hot, fires happen ...

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  • \$\begingroup\$ The question is more likely to mean why do we not fuse neutrals as well as the live. \$\endgroup\$ – Transistor Jun 23 '18 at 15:38
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The connection of the fuse to the phase is just like the protection both human being and also the electrical system against the excessive current.

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    \$\begingroup\$ Fuses do not protect human beings against excessive current. \$\endgroup\$ – Transistor Jun 23 '18 at 15:36

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