Circuit breakers are not one time use like fuses. You can think of them as reusable fuses. An in device fuse only protects if the fault is in the device. If you were to put metal in the outlet, to stop current, you need a fuse in the outlet or somewhere else between the outlet and makns, which is what US has. Circuit breakers are typically 20A (or 15A) and multiple outlets are connected to the same circuit breaker.
No. Our appliance wiring standards basically require every appliance to be able to tolerate a fault current high enough to trip a breaker. We put a 20A cord on a 500mA clock radio. If we get a short inside the appliance, it will draw enough current to trip the breaker.
The UK allows appliances to have much much lower fault current requirements than their household wiring. They can get away with this by including a current limiter (a fuse) in their plugs.
We do have provisions for fuses in plugs, but they are typically only used where we would use a lot of very low current wiring: Christmas lighting typically has a tiny fuse in the plug protecting very small wiring.
It depends on where the fault is. Starting at the input power from the cord, the first component on the circuit board is going to be a factory installed fuse. It’s probably the same on circuit boards made for UK and EU devices because it makes good engineering sense to do it that way, even if the plug is equipped with a fuse. So if the fault is somewhere on the board, it blows the appliance fuse. If it’s somewhere before the appliance fuse, it blows either the plug fuse (if equipped), or the breaker.
No, we don’t have an actual fuse in the outlet or plug. Some devices have an internal fuse, but not like the UK where almost everything has a fuse in the plug.
Circuit breakers are not one time use like fuses. You can think of them as reusable fuses. An in device fuse only protects if the fault is in the device. If you were to put metal in the outlet, to stop current, you need a fuse in the outlet or somewhere else between the outlet and makns, which is what US has. Circuit breakers are typically 20A (or 15A) and multiple outlets are connected to the same circuit breaker.
Oh right, thanks for that. So fuses in the outlet are pretty typical in the US?
No. Our appliance wiring standards basically require every appliance to be able to tolerate a fault current high enough to trip a breaker. We put a 20A cord on a 500mA clock radio. If we get a short inside the appliance, it will draw enough current to trip the breaker.
The UK allows appliances to have much much lower fault current requirements than their household wiring. They can get away with this by including a current limiter (a fuse) in their plugs.
We do have provisions for fuses in plugs, but they are typically only used where we would use a lot of very low current wiring: Christmas lighting typically has a tiny fuse in the plug protecting very small wiring.
oh, very interesting – for the clock radio example, wouldn’t the radio fry the circuit board before it tripped the breaker?
Depends on where the short was. If it was a frayed lead in the PSU contacting the neutral, that short might not even hit the board.
It depends on where the fault is. Starting at the input power from the cord, the first component on the circuit board is going to be a factory installed fuse. It’s probably the same on circuit boards made for UK and EU devices because it makes good engineering sense to do it that way, even if the plug is equipped with a fuse. So if the fault is somewhere on the board, it blows the appliance fuse. If it’s somewhere before the appliance fuse, it blows either the plug fuse (if equipped), or the breaker.
true!
No, we don’t have an actual fuse in the outlet or plug. Some devices have an internal fuse, but not like the UK where almost everything has a fuse in the plug.