The ring main certainly saved wire as more and more sockets were fitted. It also gave two paths to each socket - did Hunkin mention that?
The 3-pin round-pin domestic plugs were 15A, 5A and 2A, IIRC. Volume-wise the 13A is not that different.
The US domestic systems do have 220v capability - so they're not that different from us.
PA
Good point. Try putting a 13A load on a 13A plug. They get pretty warm even when conditions are optimal!
PA
I just watched another of Tim Hunkin's excellent videos - this one is on connectors:
In fact I can just recall the old 15 amp 3-pin plugs which preceded them and I don't think they were all that much smaller even though they were fuse-less. In North America they don't seem to worry much about safety given their lower mains voltage, but what about mainland Europe - do they use ring mains with their fuse-less plugs or does each socket have a separate run back to the fuse-box? I have never thought to enquire.
But lower voltage means higher current for the same use. So they have proportionally more house fires, due to failing connections carrying that much higher current, combined with the US favouring timber frame construction rather than bricks and mortar, compared to UK
Not quite.
There were lots of small appliances intended for use on 2A and 5A plugs, with thin flexes. And because there weren't many sockets, a lot of those appliances had long leads. Long, thin leads aren't adequately protected by a 30A fuse, so fused plugs were necessary.
There is a secondary purpose to the fuse - it limits 13A sockets to 13A max load, thus reducing high point loads which would unbalance the ring. With unfused plugs a naughty person would be able to plug their cooker into the ring circuit. In the unfused round-pin days there were hosts of adapters allowing table lamps to be plugged into 15A sockets without fusing. For some reason BS1363 doesn't require 2-way adapters to be fused, and used not to require 3-way adapters to be fused either but this has now been changed.
They usually use 16A or 20A radial circuits, and modern appliances have thick (or short) enough flexes that they are adequately protected by a 20A MCB.
Owain
A bit slack with the past and present tenses.
8 min 46 sec "so it was extremely safe"
From a pedantic POV, the USA has 120V between live and neutral. It can also have 240V or 208V depending on the supply. 208V being from 2 legs of their 3-phase supply.
They were bigger.
Bill
Not wuite, they have 3-phases in the street but their transformers (pole pigs) have centre tapped secondary so it gives +110V/N/-110V to the house, most circuits use a single live (hot) to neutral, but heavy duty stuff like tumble driers use both hots
They are bigger. Still used in theatres. ^^^
I remember when the sockets in the workshop at the place where I worked were converted from 15A to 13A to bring them up to date and make them compatible with more kit. They were still on individual radial circuits rather than a ring.
We had a problem with an arc welder which had been fine with an unfused
15A plug but kept blowing fuses in its 13A plug - until some bright spark had the idea of turning up a solid brass "fuse" on the lathe. we didn't have any more problems then! [*And* it was no less safe than the earlier arrangement apart perhaps for the risk that the plug would overheat because square pins into metal strips are nothing like as robust as round pins into close-fitting round tubes.]
And a lot more robust.
The reason for that is if a plug had a fuse in it and it blew during a live performance, it was not a quick or safe job to get a maintenance man out to climb into the suspended walkways in the dark, find the plug, unplug it, take it apart, replace fuse, reassemble the plug, plug it back in and vacate the suspended walkways.
instead, the arrangement was a wall of MCBs or fuses immediately after the lighting power thyristors controlled by the lighting desk.
They were on the wall in the same room as the lighting engineer.... so if a circuit pops, the lighting engineer had to reset/replace the MCB/fuse there and then instead.
1) First all the guy in the video is correct. 2) The voltage is 120V but also 240V or 208V depending on the supply.
HTH
just cut the correct length off a metal potentiometer spindle. They were the right diameter
Apart from the fuse making it larger part - Then that is the thrust of it. A ring can serve lots of sockets with less cable and is easier to wire if you need a high power delivery. It could also be cobbled together from two existing 15A radials, and be far more versatile than the sum of the parts. The modern implementation of the ring turning out to be very well suited to modern applications (i.e. loads of sockets and load of small loads)
Indeed - if anything they are larger.
They don't but ought to (the number of electrocutions there per year are staggering compared to ours!)
Most places use lots of radials serving just a few sockets, with the MCB sized to offer both fault and overload protection to all of the circuit, right up to the appliance.
(contra you our design where the MCB[1] offers fault and overload protection for the ring circuit as far as the sockets, but the plug fuse extends fault protection up to the inlet of the appliance).
[1] in conjunction with some design rules.
You wouldn't want to be climbing up into the lighting gantry at the interval to change a fuse.
Bill
Not all of them accidental.
Bill
When I was young we had DC mains and the cooker control box had fused
15amp and 5 amp round pin sockets. The switches were the two pole rotary type. All my experiments were done, using an ex WD rotary transformer used in reverse, to get ~28volts DC.
Does anyone remember this monstrosity?
Chris
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