Why Fuse is Not Placed in Neutral Wire

Gross generalizations:

A) No amount current in the Neutral could be there unless it came from the phases (or Hot). So in effect, if you have fusing n the phases, you have protection of the neutral.

B) If a fuse was put in the neutral of a 3 phase Wye / Star system and it opened, you phase voltages would be floating, not good. If you have a North American single phase system, an open neutral would not be as bad, but t is a waste.

The most reason is there is a major safety concern to this.

Simply think a single lighting circuit where you have fuse in neutral and if it is blown and you see the light is off. You thought there is no power supply (STOP: there is power supply) and carelessly try to repair it. Think about the case may happen to you.

For the same reason, it is not allowed to use disconnect switch in the neutral line.

Hope it is clear now.

- MS

D'oh!

That too!

I may have an exception to this:

Portable equipment on plastic casters with no part touching any grounding surfaces and fed by a three phase source with no neutral. (think 208VAC in USA with standard 4 wire plug as installed on portable equipment) The equipment has a control panel with the ground conductor connected to the panel and back plane. A meter is installed in the control panel that operates only on 120VAC. You do not want to use ground as a neutral in this case, since, if ground is ever broken in the cord feeding the panel, the 120VAC is connected to the equipment body. Therefore, you use a stepdown transformer to 120VAC, but the leg that would be neutral and connected to ground, must float, and therefore should also be fused. Isn't this essentially a "fused neutral"?

Thanks for your answer. It helps me.

It's contrary to British Standard 7671.

Were it to be there and to be removed for, oh, say, the replacement of an Edison-screwed lamp, although the lamp would be off the circuit would still be connected to the live conductor, and a shock remains possible.

Don't fuse neutrals!