Live and neutral are typically not interchangeable. fuses should be on the live cables so that over current is stopped on the way in. Plugging in the wrong way means that a blown fuse might stop current, but the device could still be at live voltages and be dangerous.
that’s why you put fuses in central fuse box, not in the plug. appliances should be designed in such a way that it shouldn’t be a problem. nobody else does this because it’s not necessary if your installation is sanely built
The central fuse boxes only protect the house wiring. You need a lower rated fuse for individual devices. That 30A central fuse ain’t gonna protect the wiring inside your 6A lamp.
yeah that’s what separate fuses for separate branches of circuit are for, all in one central box because where else are these supposed to be. if your lamp is wired with 6A-rated wire then that branch should be fused with 6A fuse, which on its own is unhinged because usually much thicker wires are used anyway
This is the reason why uk home electrical wiring has fuses everywhere. It is a safety measure that mitigates other problems like poor design and bad installation practices
A fuse/breaker at the fuse box needs the current capacity for all, or at least most devices on at the same time. The individual fuses can be rated much lower.
uk fuse in fuse box can’t be sized properly because old uk installations used ring circuits in order to save copper during ww2 shortages, everybody else has this problem sorted out by now (initially by using aluminum wiring, or waiting for more copper). modern wiring is arranged in star-type topology with a few outlets per leg, and it can be fused properly, but the far out parts of circuit don’t transmit power at all times which is why it was looked down upon during shortages
example would be 16A circuit that has 5-10 16A outlets, has wires suitable to carry 16A and 16A fuse. it’s okay because you’re not expected to draw full power at all outlets at the same time, and most of the time much less than that. if you do and you know it in advance you’re expected to split it over more circuits, or make it bigger. uk ring circuit would have wires that carry only 8A in each direction, and fused 16A. it can fail in a way where one side disconnects, but the other side becomes overloaded. plug fuses are for protection of these shitty circuits from shortcircuit in appliance
Do UK ring circuits rely on a single breaker at the fusebox? I assumed that they would have a breaker for each leg of the ring (8A + 8A in your example).
That sounds really dangerous as a cut ring would be fused at double the current capacity of the wire. Would the wire in your example be rated at 8A or 16A?
I have little to no knowledge of the UK power setup but have heard that its meant to be pretty safe. What am I missing?
you’re not missing anything, it’s an unhinged tradeoff that you do because you need to conserve copper for brass casings because nazis are in calais, there’s zero reason to do this today. apparently it’s still allowed in uk for some unthinkable reason but i haven’t heard of it anywhere else. yes, single fuse *per ring is used, rated at double what it would be in star/radial circuit
you don’t even need a fault, sufficient asymmetry in ring geometry or load distribution already will cause this problem
60yr old house in the UK, we have one breaker per socket circuit for example. It uses 2.5mm wire which can handle 30A, so that would be the max recommended fuse rating at the breaker. That way it’s still protected if there is a break in the circuit anywhere.
We also have a separate lighting circuit with 1.5mm wire and a lower breaker fuse rating.
It can lead to some annoying fuckery though. I recently updated a ceiling light and was frustrated at why it wouldn’t switch on after triple checking every connection. Had to get out a multimeter and investigate all over the house. Turns out at some point in the past a previous homeowner had not bothered to connect the neutral wire back to the fusebox at an entirely different ceiling light, leaving the neutral floating. It was sitting at 110V rather than zero. Somehow it was OK to do that with old lights.
Such as… putting a fuse in the appliance making repairs more difficult. A breaker box stops extreme overcurrents, but a measly 0.5 amps could still cause a fire.
Polarized live/neutral is still insane to me. All it takes is one cheap electrician or overconfident DIY to introduce a potentially lethal false sense of security.
Live and neutral are typically not interchangeable. fuses should be on the live cables so that over current is stopped on the way in. Plugging in the wrong way means that a blown fuse might stop current, but the device could still be at live voltages and be dangerous.
that’s why you put fuses in central fuse box, not in the plug. appliances should be designed in such a way that it shouldn’t be a problem. nobody else does this because it’s not necessary if your installation is sanely built
The central fuse boxes only protect the house wiring. You need a lower rated fuse for individual devices. That 30A central fuse ain’t gonna protect the wiring inside your 6A lamp.
yeah that’s what separate fuses for separate branches of circuit are for, all in one central box because where else are these supposed to be. if your lamp is wired with 6A-rated wire then that branch should be fused with 6A fuse, which on its own is unhinged because usually much thicker wires are used anyway
This is the reason why uk home electrical wiring has fuses everywhere. It is a safety measure that mitigates other problems like poor design and bad installation practices
its not, it was put into place due to copper shortages during ww2
more like papers over poor design informed by ww2 shortages
A fuse/breaker at the fuse box needs the current capacity for all, or at least most devices on at the same time. The individual fuses can be rated much lower.
uk fuse in fuse box can’t be sized properly because old uk installations used ring circuits in order to save copper during ww2 shortages, everybody else has this problem sorted out by now (initially by using aluminum wiring, or waiting for more copper). modern wiring is arranged in star-type topology with a few outlets per leg, and it can be fused properly, but the far out parts of circuit don’t transmit power at all times which is why it was looked down upon during shortages
example would be 16A circuit that has 5-10 16A outlets, has wires suitable to carry 16A and 16A fuse. it’s okay because you’re not expected to draw full power at all outlets at the same time, and most of the time much less than that. if you do and you know it in advance you’re expected to split it over more circuits, or make it bigger. uk ring circuit would have wires that carry only 8A in each direction, and fused 16A. it can fail in a way where one side disconnects, but the other side becomes overloaded. plug fuses are for protection of these shitty circuits from shortcircuit in appliance
Do UK ring circuits rely on a single breaker at the fusebox? I assumed that they would have a breaker for each leg of the ring (8A + 8A in your example).
That sounds really dangerous as a cut ring would be fused at double the current capacity of the wire. Would the wire in your example be rated at 8A or 16A?
I have little to no knowledge of the UK power setup but have heard that its meant to be pretty safe. What am I missing?
you’re not missing anything, it’s an unhinged tradeoff that you do because you need to conserve copper for brass casings because nazis are in calais, there’s zero reason to do this today. apparently it’s still allowed in uk for some unthinkable reason but i haven’t heard of it anywhere else. yes, single fuse *per ring is used, rated at double what it would be in star/radial circuit
you don’t even need a fault, sufficient asymmetry in ring geometry or load distribution already will cause this problem
60yr old house in the UK, we have one breaker per socket circuit for example. It uses 2.5mm wire which can handle 30A, so that would be the max recommended fuse rating at the breaker. That way it’s still protected if there is a break in the circuit anywhere.
We also have a separate lighting circuit with 1.5mm wire and a lower breaker fuse rating.
It can lead to some annoying fuckery though. I recently updated a ceiling light and was frustrated at why it wouldn’t switch on after triple checking every connection. Had to get out a multimeter and investigate all over the house. Turns out at some point in the past a previous homeowner had not bothered to connect the neutral wire back to the fusebox at an entirely different ceiling light, leaving the neutral floating. It was sitting at 110V rather than zero. Somehow it was OK to do that with old lights.
Such as… putting a fuse in the appliance making repairs more difficult. A breaker box stops extreme overcurrents, but a measly 0.5 amps could still cause a fire.
Polarized live/neutral is still insane to me. All it takes is one cheap electrician or overconfident DIY to introduce a potentially lethal false sense of security.