Dumb question incoming

[atm84]

I actually saw a TPN service head which had 4 fuses and a neutral emanating from one if then. This was done in the late 90s and when I raised it with the Senior Engineer he said it would have been a solid link but not sure why it was there in the first place.

 

[davesparks]

I actually saw a TPN service head which had 4 fuses and a neutral emanating from one if then. This was done in the late 90s and when I raised it with the Senior Engineer he said it would have been a solid link but not sure why it was there in the first place.

It will be a solid link installed as a means to disconnect the neutral if required.

 

[tazz]

Back in 1947 the now British Standard (BS 1363) 13A plug and socket were introduced. These have ALWAYS had a fuse in the live only connection at both the consumer (fuse) board and in the plug. They also have shutters to prevent anything entering the socket except a plug!

The reason for only the live fuse is that back at the sub station, neutral is strapped to earth. Even on a high current path, this is no more than a few volts above earth, and is therefore safe. Blowing the fuse removes all dangerous voltages from the equipment. a fuse in the neutral, on the other hand, would leave the appliance with a lethal 240v RMS AC on all working parts.

Also note that the "Shaver socket" actually removes the neutral strap to make it safer in bathrooms and the like. Touching just one conductor will make that the floating connection and the other pin will have the dangerous 240v. It is also fused at just 1A.

Alan As much as I see you points and cannot disagree...They dont explain the original question of why the neutral was fused, and not what the faults are...Isolation transformers are not really and issue her either.

 

[Geordie Spark]

Back in 1947 the now British Standard (BS 1363) 13A plug and socket were introduced. These have ALWAYS had a fuse in the live only connection at both the consumer (fuse) board and in the plug. They also have shutters to prevent anything entering the socket except a plug!

The reason for only the live fuse is that back at the sub station, neutral is strapped to earth. Even on a high current path, this is no more than a few volts above earth, and is therefore safe. Blowing the fuse removes all dangerous voltages from the equipment. a fuse in the neutral, on the other hand, would leave the appliance with a lethal 240v RMS AC on all working parts.

Also note that the "Shaver socket" actually removes the neutral strap to make it safer in bathrooms and the like. Touching just one conductor will make that the floating connection and the other pin will have the dangerous 240v. It is also fused at just 1A.

Aye, that's champion bonny lad and must have taken ye a good while to type it all oot and the lads here are not unappreciative of your sterling efforts, but WHY did me Granny's fuse box have BOTH a line AND neutral fuse in it??

THAT was the question!!!

 

[Knobhead]

So what you're saying is you don't know either!!

TONY !!! ..... any ideas???

On larger DC systems the power would be distributed as 440V +→-.

Locally Balancer sets would drop this to 220+/N/220- for domestic use, the neutral being referenced to ground. (You’ve seen the drawings of them elsewhere).

Smaller systems would be 220V +→- with no reference to ground so fused on both +&-.

Some works such as collieries would build villages for their workforce. These were supplied at what ever the colliery used. I know of one village near Mansfield where one side of the road was on 120V 33Hz, the other side of the road 200V 12.5Hz.

That should cover the old service heads with fused neutrals, they are a dangerous hangover that if you find them bang a report in to the DNO.

With AC neutral is normally referenced to ground but not always. Earth free can be needed in some cases, our furnaces were 660V earth free two wire.

Earth free systems are a pain in the arse, it to me four months to find an intermittent earth fault.

 

[Engineer54]

As many have stated it was a leftover from the DC era which were based on local supply set-up's. Each area, town, city in those days chose the system they wanted or could afford, nothing was standardised, ...that came later. So the rough reasoning behind Neutral fusing is pretty much how Tony has described above, a bit more to it than that, but good enough.

Even when the supply changed to AC electrical installations were pretty crude or basic to say the least especially for domestics, where it was mainly a lighting installation with perhaps one or two (if you were lucky) socket outlets per house or apartment/flat. It took a time for the industry to get used to the AC supply systems and rewrite the Regs of the time to accommodate and eventually standardise. Some local regional electricity boards were still installing fused neutral cut outs some 15 to 20 or so years after the general AC changeover was completed...

 

[Geordie Spark]

As many have stated it was a leftover from the DC era which were based on local supply set-up's. Each area, town, city in those days chose the system they wanted or could afford, nothing was standardised, ...that came later. So the rough reasoning behind Neutral fusing is pretty much how Tony has described above, a bit more to it than that, but good enough.

Even when the supply changed to AC electrical installations were pretty crude or basic to say the least especially for domestics, where it was mainly a lighting installation with perhaps one or two (if you were lucky) socket outlets per house or apartment/flat. It took a time for the industry to get used to the AC supply systems and rewrite the Regs of the time to accommodate and eventually standardise. Some local regional electricity boards were still installing fused neutral cut outs some 15 to 20 or so years after the general AC changeover was completed...[/QUOTE]

They probably had warehouses stuffed full of the things and needed to get rid of them!