> It would need to be a 6A fuse in the US. Watts = Amps * Volts, or Watts / Volts == amps.
My point was that the (up to) 3A UK device gets 3A fuse in the plug in the UK. In the US that device becomes a 6A device but (essentially) gets a 15A fuse in the breaker box, is that the case? Because that seems worse.
A fault in the device blows the plug fuse in the UK. The same fault needs to trip the 15A one in the US.
> A breaker on each of those ring circuits is essentially a ‘whole house breaker’, and would not trip on a whole host of ‘everything is melting’ situations.
I don’t know what this means. It will trip for currents greater than its rating. Nothing should be melting under its rating.
The rating on a UK ring circuit breaker is so high that you can literally melt significant quantities of steel without tripping the breaker, and certainly can turn typical appliance wiring incandescent, also without tripping the breaker.
The rule for electrical systems is that any downstream wiring/circuit that would catch on fire in the event of a fault, needs to have a breaker in the circuit before that point, that will interrupt the circuit before the point it would catch on fire.
In the US, every device is just constructed to be safe up to 15/20amps, which uses a bit more copper but is not really a major problem.
But the current is so much higher in the UK, and that is why the fuses on the plugs, because without the fuses providing a lower cut-off point, at a minimum the wires to a typical lamp or whatever, at least to the point it has a fuse or circuit breaker, would need to safely be able to carry the full 32A/220v load without catching on fire.
Which is a very thick cable. And quite a bit more expensive than the tiny bit of extra copper needed to get to 15/20A from 6A.
Does that make sense? The UK plugs essentially distribute the job of overcurrent protection to every single devices plug, where everywhere else it is more centralized at the (lower capacity) circuit level.
As to if this is better or worse is more a matter of opinion and specific local economics that have changed over time than a resolvable ‘fact’.
It all makes sense in that it confirms the crazy thing I couldn’t believe was true at the beginning - US appliances have the ability to sink a ton more current than they would ever need under normal operation, which seems like a safety issue. Would you want your electric toothbrush charger sinking 15A in some fault condition?
A UK device blows its own fuse under these circumstances. The wasted copper in every US appliance cord is just insult to injury.
> The rating on a UK ring circuit breaker is so high that you can literally melt significant quantities of steel without tripping the breaker
That’s fine, as long as everything is rated to that draw and doesn’t melt. If the wires couldn’t handle it then the breaker would be rated lower.
> certainly can turn typical appliance wiring incandescent, also without tripping the breaker.
And that’s where the fuse “shines”!
Seems like the UK method uses less copper and gives finer control in over current scenarios. I don’t see any benefits of the US style.
The US style also has much smaller and cheaper plugs, and the cords are all basically the same size anyway. I don’t recall any UK appliances being notably less bulky or anything either (though when running 220v, you can have electric kettles which aren’t lame, which is nice).
Notably, pretty much everywhere else in the world also uses similar branch circuit type designs and 220v and their plugs and appliances are also not notably more bulky either.
The difference in wire diameter between say 6amps and 15 amps isn’t that noticeable. 15 and 30 is.