Understanding fused spur

[JohnW2]

Well I could go with that BUT I almost never ever used 4mm T & E for many years of my working life (mostly on domestics) ....

Yes, but as I said, there would be virtually no point in having a 4mm² ring final, since it would not enjoy any of the 'relaxations' of regs which exist with a 2.5mm² ring final. As I said, the only real 'benefit' being CPC redundancy, plus some even more trivial things (e.g. less VD and hence less 'energy wastage' during Summer!

4mm² 32A radials are probably becoming more common but, apart from that, I don't imagine that a lot of 4mm² does get used (even though it would presumably be adequate for many 'cooker circuits'). I must say that I personally find 4mm² T+E nice/easier to work with than 2.5mm².

 

[EFLImpudence]

When new things become compulsory do people think it unreasonable on the grounds that not many people have been using them?

 

[JohnW2]

When new things become compulsory do people think it unreasonable on the grounds that not many people have been using them?

Do you mean things like RCDs and ('almost') SPDs?

 

[EFLImpudence]

Anything.

It appears some people's argument against making 4mm² compulsory for ring circuit spurs is that not many people have any.

 

[Jurassicspark]

If the problem were due to the cable having been 'overloaded' it presumably would have affected the entire length of the cable. If the cable was only damaged close to the switch, that presumably was due to poor/loose connections to the switch - something which seems pretty common with 'shower isolators'.

I'd say the cable will be running warmer than it ought to, because the current is higher relative to the conductor size then you’ve got a loose connection at the switch.

What does that mean?

Higher resistance at that connection point, which means even more heat right there.

What do you mean by 'each leg' - both the supply and load side of the switch, perhaps?

Too much pottering around with the topic of ring circuits probably.

 

[SUNRAY]

I must say that I personally find 4mm² T+E nice/easier to work with than 2.5mm².

Interesting, personally I find the opposite is the case, especially when clipped direct.

 

[EFLImpudence]

I find it nicer/easier than 2.5mm² as well.

What difference does clipping direct make?

 

[SUNRAY]

Indeed I have been to bungalows, the info I put about rings have been in vogue at one time or another as being so called official guidance by the great and good or so for quite a few years each.
Exactly why it was taught than no more spurs than on the ring proper became a well adopted rule I have no idea and as such as far as I am concerned if you had 12 points on the ring and each one fed a spur and between each point on the ring you had another 13 points and then from the fuseway you had two points you would certainly have a lot more on the end of spurs than on the ring itself but what would it matter.
Similarly you might have zero points on the ring proper and 100 points spurred from the ring and what would that matter either?

The only reason I could envisage is to reduce hap hazard thinking/good housekeeping or good planning as against adding things piecemeal.
But why were such things taught? I do not know!

Some of the rules are made and adhered to are done so as a good practice (sometimes) even though the regs might not actually state them.

Years back I saw a good many ring mains (as the vast majority referred to them) where the original single socket radials had been converted by adding a JB under the floor to make each socket a spur and any additional sockets added were frequently installed in the same way, so none or very few sockets on the ring but all or most were spurs.

 

[SUNRAY]

I find it nicer/easier than 2.5mm² as well.

What difference does clipping direct make?

I find it easier to make 2.5mm² clipped direct look tidier than 4mm², I always preferred 2.5mm² over 7/0.029" and 1/0.044" over 3/0.029" for the same reason

 

[SUNRAY]

I find it nicer/easier than 2.5mm² as well.

What difference does clipping direct make?

I find it easier to make 2.5mm² clipped direct look tidier than 4mm², I always preferred 2.5mm² over 7/0.029" and 1/0.044" over 3/0.029" for the same reason


EDIT: I have no idea how this double post happened some nine hours later.

 

[ebee]

When new things become compulsory do people think it unreasonable on the grounds that not many people have been using them?

That`s a good question.

Old habits die hard (not just in Electrics but also in many aspects of modern life).
I`ve known a customer or three not liking me putting a socket in a new place rather than around the existing one and they did not like it because they were so used to using it in a more difficult and/or a sometimes potentially less safe place.
People are not always logical even when they try to be.

 

[securespark]

I found the stranded imperial stuff easier to work.

There was a short period in the 80s where 2.5 stranded T&E was available, but it disappeared.

I know you can get the harmonised variety today.