Why did the UK change from round pin to square pin plugs?

I'd say most radios were AC only by then. Having a mains transformer. Although universal types still around.

BBC TV was the same. Later version was known as Walsall gauge - all the pins were rotated 90 degrees. Think LT used those for 110v.

Because the maximum current thru it is less than half of that in a ring.

Less copper is used in a ring because there are only 2 connections to the CU. There is a connection to the CU for each radial and a lot more radials than there would be with a ring.

Because that would use more cable than a radial.

In that case the fuse is protecting the cable to the GPO, not the cable between the GPO and the appliance has a fuse with all except lights.

They can install rings if they want (we checked when we were wiring a holiday home, in France in the early '90s), but they are used to spurs and probably won't change from what they know.

Since the late '70s, early '80s (IIRC) it has not mattered anyway, as the adapters are required to be fused themselves, so the first in the chain will protect them all.

That's only if it has been artificially limited to 16 amps (in a continental system AIUI). If you stick with the 16 amp fuse then surely the cable in a ring would be thinner because the current has two paths to the consumer unit? I thought this saving of copper was the motivation for the change in the first place.

Quite. This is the point I am making. Why do the continentals have long 16 amp radials instead of a ring? Where is the benefit of a radial circuit when someone has said it would only take two heaters (or similar) to crash it out?

I thought we agreed a ring used less cable.

You are confusing me entirely now. Are you saying that all appliances (except lights) fitted with a europlug (Type C) have an internal fuse? Do they make a special 2.5 amp fuse? Is this replaceable or do they just throw away the appliance if a fuse blows? How can it be 'except lights' anyway. Lamps can fail too and it would be fairly bad news to pump 16 amps through a 2.5 amp plug.

Nothing artificial about it, the radial system for GPOs specifies how many GPOs are allowed on each radial.

No, because the ring has all the GPOs on it and so needs to carry much more than 15A to be viable.

Yes, but it saves copper by only having two connections to the CU instead of one for each radial. And having twice the current carrying capacity doesn't double the amount of copper used.

Because they didn't care about the extra copper needed.

The benefit is with the other benefits I listed.

You don't have just the one radial instead of one ring.

Yes,

Or something similar like a thermal cutout. Often seen in fan heaters.

Don't need one.

Usually.

Not often. Some stuff like TVs and set top boxes etc do have a soldered on pcb fuse which can be replaced.

Because that is how the system evolved. It started with lights.

Yes, and can short too.

Not when it takes out the CU fuse or trips the breaker quite quickly.

And not all lights have 2.5 amp plugs, most plug into normal GPO sockets.

Similarly, it is perfectly OK to install a "European" system (complete with "European" sockets in the UK due to the wonders of harmonised regulations.

John

On Sat, 25 Jun 2022 05:14:10 +1000, hgt snipped-for-privacy@nurk.com wrote: [snip]

That I did not appreciate.

That depends on the size of the ring. There is nothing to prevent having several rings. As

That's what I thought (although mechanical strain on the socket could be an issue) but you said they were designed not to be stackable when it seems they are stackable.

It wasn't me. I only said that they were fused, so load was not an issue.

Yes, but at the time it was introduced to save copper, there would normally only have been the one ring in most houses. And even with mega ancient mansions, there would normally have been fewer rings than if radials had been used instead.

Not clear what happened there. Looks rather like you accidentally hit post and didn't notice or something.

Take a look at a domestic American 'breaker panel'. Yep, they have a ton of breakers. I think they get 2 or 3 sockets per radial, but not sure on that point

no, there were lots.

I dunno if hgt is Rod or not. Anyway, once you have several sockets, rings use way less cable. It's trivial to draw it on paper.

That's a non-sequiter. Fuses don't trip the moment you overload them slightly, they allow large overcurrent. And extension leads & adaptors do not tolerate large overcurrent.

It is nothing like that low.

Exactly what happened here.

I decided the extent of any real disagreement was very limited and I should leave the subject for others to comment (or not).

Sorry, it was Animal.

Whether they are stackable or not is academic as any sensible person would use a power strip rather than two or three adapters plugged into each other.