[sbradford26]

Largely this is resolved by US houses having a lot more circuits. My bathroom has a dedicated 20 amp (2.4 kW) circuit for the outlets and a separate 15 amp (1.8 kW) circuit for the lights. Every bedroom in my house has its own 15 amp breaker. The kitchen has 3 20 amp breakers for different wall outlets, a 15 amp breaker for the lights, then a 30 amp 240v (7.2 kW) breaker for the cooktop, and a 20 amp 240v (4.8 kW) breaker for the oven.

For the a typical US house the standard feed into the house is 200 amps at 240v. So 48kW of power coming in we just segment it down a lot more.

[bialpio]

It starts to become annoying when you have a home office for 2 people though. 2 PCs + 4 monitors and some random things in a room can start approaching the wattage limit. Especially given that I think it's not too common to have one circuit per room (anecdata: my house has one circuit for all outlets per story; not counting bathroom and kitchen which I believe are mandated by building code to be separate).

[hajile]

Lots of smaller (kw) circuits is safer than a few very large circuits. The NEC in the US actually stipulates that you must use different receptacle styles for higher ampacities specifically because it is less dangerous. If you run a small appliance on a 30-40amp circuit, you run the risk of that seemingly safe appliance pulling the full 40+ amps required to trip the breaker

[bialpio]

Not sure if I understand - can you clarify? Did you mean that a normally safe 1.5kW appliance runs the risk of cooking itself if it's connected to a 40amp circuit? If yes, then sure, that makes sense.

> Lots of smaller (kw) circuits is safer than a few very large circuits.

Not fully convinced about the safety aspect but it definitely feels more convenient (can selectively turn rooms off if you need to work on something) - if I'm ever opening the walls, I'm going to switch to that approach. At the very least, I want to have a dedicated 20amp circuit in the home office...

[sbradford26]

Largely yes a 1.5 kW device (a 12.5 amp space heater for example) is less safe on a 40 amp circuit. Since if it fail pulling more load than designed but not truly shorted the breaker may not trip. But if you put that space heater on a 15 amp circuit it would most likely trip the breaker. As other commenters have said the UK addresses that risk with fuses in the plug.

Also I recently redid my kitchen and I added an additional 20 amp circuit just for the kitchen island outlets and it has been super nice.

[bialpio]

Are safety concerns alleviated here by GFCI breakers? In what cases could this appliance pull more amps than it was designed for? I know it's not required for circuits outside kitchen and bathroom, but I was thinking about just replacing all the breakers with combined GFCI/AFCI ones (especially given that my circuits are so old that there's no ground on them, in which case code I believe mandates that the outlets are GFCI-protected and labeled as "no ground").

[sbradford26]

So the risk would be reduced. Since if the failure causes a electricity to travel anywhere other than the neutral it will cause the gfci to trip. A scenario where a device would pull more power would be a short developing in a heating element reducing its resistance. So it would just pull more power but all of the power is still going to the neutral and wouldn't trip the GFCI.

Also with replacing all your breakers it can increase safety. But first the breakers are not cheap. Second it can lead to a lot of nuisance trips, albeit that is better than it used to be with modern breakers.

[bombcar]

GFCI is not a magic “make everything perfectly safe” - you could electrocute yourself to very dead without tripping a GFCI if all the power went down the main wires and none went to ground.

[Symbiote]

Britain solves this with fuses inside appliance plugs.

The continental European system doesn't really solve it, as far as I know, so you have thicker wires on low power appliances than you would in the USA.

[sbradford26]

The US also has fused plugs but their are not widely used for some reason. I see them mostly on Christmas lights, but I have also seen it on some small home electronics like a window fan and air purifier.

[bombcar]

That’s usually because the lights draw such little power that a short at line amperage could turn them very hot without tripping a breaker.

The fuse prevents that.

[sbradford26]

Yeah sadly having separate circuits for each room is not required by the NEC to the best of my knowledge (and might be overkill depending on the situation). Usually though best practice is to have a separate circuit though for each bedroom. Depending on how your outlets are wired it might be possible to split them off onto separate breakers relatively easily though.