no fuse in the Neutral conductor

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electrics

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hello, i wonder when it is dangereous or not wanted by codes especially, to mount a fuse-link on a neutral? is there any generalisations over this issue?
 
roger

roger

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240.22

240.22 Grounded Conductor.
No overcurrent device shall be connected in series with any conductor that is intentionally grounded, unless one of the following two conditions is met:

(1) The overcurrent device opens all conductors of the circuit, including the grounded conductor, and is designed so that no pole can operate independently.

(2) Where required by 430.36 or 430.37 for motor overload protection.
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That pretty much eliminates the use of a fuse.

Roger
 
iwire

iwire

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electrics said:
i am trying to figure out what hazards can be ? please explain these a bit more in detail. Best Regards...
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Lets say you supply a 120 volt machine with a fuse on both the neutral and the hot. Now lets say the neutral fuse opens, now the equipment stops working but there are still live conductors in the equipment and if someone was to go messing around with it they could be injured.

Take the above with the fact that there is no need to protect the neutral and I think you can see why the NEC prohibits it.
 
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broadgage

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And remember also that until recently, the NEC permited the frame of a range or cloths dryer to be grounded to the neutral, rather than to a dedicated EGC.
This is no longer allowed for new installations, but many old ones remain in use.
The opening of a fuse in such a neutral conductor would be very dangerous since it would result in line voltage on the case of the appliance.

Regulations here in the UK differ from the USA, but still prohibit a fuse, or a single pole switch, or a single pole circuit breaker, in the neutral.
Multi pole switches and circuit breakers that open the neutral and all assoiciated live/hot conductors are permitted, and in some circumstances required.
 
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