Is any more proof needed ?

[JohnW2]

I don't understand why RF doesn't stand for Radial Final.

It does

..... amoungst other things

Kind Regards, John.

 

[Paul_C]

To me it will always primarily mean radio frequency.

 

[JohnW2]

To me it will always primarily mean radio frequency.

Me too ... that's definitely one of those 'other things' it can mean!

Kind Regards, John.

 

[SimonH2]

Erm...fused plugs are necessary.

Why? Most of the rest of the world gets along without them just fine.

Hmm, would you consider a 0.75mm2 flex to be adequately protected by a 20A or 16A MCB ?

If you don't have fused plugs then you have two conflicting requirements. Users don't like excessively heavy cables - and wouldn't take kindly to every low powered device having to have a cable capable of being protected by such a large protective device rating. On the other hand, if you use cables sized appropriately to the load then they won't be protected.

The alternative is to return to a system with different sockets for different uses - which is of course quite inconvenient. From what little I've seen of French and German installations, they end up with large breaker panels and a large volume of cabling.

Clearly, if you don't have fused plugs, the idea of a 32A radial in 4mm2 cable becomes quite impractical. So you need a lot more radials, and effectively separate circuits wherever large loads are anticipated. If (say) 16A was the accepted protection rating, then you'd better have a lot of separate circuits into a modern kitchen !

Incidentally, when we moved into our house, quite a few of the sockets had one 13A socket and two 2A light sockets protected by a BS1363 fuse. I suppose that would go some way to the fusing issue - but then re-instroduces the problem of different plugs and the issues of having spare sockets - but not the right type.

 

[JohnW2]

Hmm, would you consider a 0.75mm2 flex to be adequately protected by a 20A or 16A MCB ?

Obviously not in terms of current regs, but I guess that, in talking about different wiring strategies, we're implicitly consdering the possibility that the regs could be revisited, and revised.

So, on that basis (and I'm sure you're not going to like it) .... as I see it, the chances of a 0.75mm² flex attached (appropriately in terms of the load) to some appliance or equipment being overloaded (e.g. finding itself carrying a current between 6A and, say, 30A) are extremely small - for appliances to create such 'sustained overloads' is a very unlikely scenario. In the case of a fault situation, when the fault current would be much higher than that overload current, although I'd have to do some sums to check, I very much doubt that a 0.75mm² flex would actually come to any harm in the very brief period before an OPD operated.

Kind Regards, John.

 

[ban-all-sheds]

Hmm, would you consider a 0.75mm2 flex to be adequately protected by a 20A or 16A MCB ?

Against what?

Overload or fault?

On the other hand, if you use cables sized appropriately to the load then they won't be protected.

Protected against what?

Overload or fault?

From what little I've seen of French and German installations, they end up with large breaker panels and a large volume of cabling.

And your point is?

Clearly, if you don't have fused plugs, the idea of a 32A radial in 4mm2 cable becomes quite impractical. So you need a lot more radials, and effectively separate circuits wherever large loads are anticipated. If (say) 16A was the accepted protection rating, then you'd better have a lot of separate circuits into a modern kitchen !

And your point is?

Once upon a time it was the norm for houses to have 4 circuits.

Now the norm for exactly the same house is more than 4.

Things change.

So what.

 

[Paul_C]

For the overload vs. fault issues already mentioned above, most Continental countries are quite happy with 0.75 sq. mm flex on 16A branch circuits. Admittedly it's a slightly larger conductor, but the American NEC has also long accepted a #18 conductor (about 0.823 sq. mm) as being adequately protected when plugged into a receptacle on a normal 15 or 20A branch circuit.

By way of comparison, back when metric-sized flex was introduced here the IEE decided that 0.75 sq. mm would be adequately protected by a 13A BS1362 fuse. Before the change, 23/.0076 (0.645 sq. mm) was also accepted with a 13A BS1362 fuse, and 40/.0076 (1.09 sq. mm) on a 15A BS3036 fuse (i.e. what was termed coarse protection at the time).

In practice, 23/.0076 (and 0.75 sq. mm when introduced) cords on lamps and other small appliances often ended up having 15A BS3036 protection anyway, since they were commonly wired to 5A BS546 plugs.

 

[SimonH2]

Hmm, would you consider a 0.75mm2 flex to be adequately protected by a 20A or 16A MCB ?

Against what?

Overload or fault?

Both

On the other hand, if you use cables sized appropriately to the load then they won't be protected.

Protected against what?

Overload or fault?

Ditto - both

From what little I've seen of French and German installations, they end up with large breaker panels and a large volume of cabling.

And your point is?[/quote]
Part of the discussion was the amount of copper used for radials vs rings. Clearly, if you end up with a lot of radials, it doesn't take long before you are putting a lot more copper in.

Clearly, if you don't have fused plugs, the idea of a 32A radial in 4mm2 cable becomes quite impractical. So you need a lot more radials, and effectively separate circuits wherever large loads are anticipated. If (say) 16A was the accepted protection rating, then you'd better have a lot of separate circuits into a modern kitchen !

And your point is?

If you were to run a radial with 30A/32A protection, then the issues of small flexes protected by high amperage protection becomes more pronounced.
Once you have the capability for <something> to draw 30A from a socket, then you get two issues - one relates to protection for the flex on small appliances, the other relates to users deciding to run larger appliances off inappropriately rated accessories.
If instead of 32A you decide the radials are going to have 16A breakers (or even 20A) then the scope for nuisance tripping becomes more significant. Thus you are likely to want more radials to get the diversity.
In a kitchen you obviously have multiple appliances with large loads - so you end up with a situation where many combinations of two appliances will trip a breaker. Not acceptable to most people.

And yes I know we used to have just 4 circuits, but so what ? That's got nothing to do with the current thread as far as I can see. Things change, no one is suggesting we go back to just one socket in each room - at least I don't think they are !