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This is fascinating! I did not know this about british plugs. Why is that? Is it a safety measure?

tjohns 3y ago
British household electrical systems are normally built as one large ring circuit, originally in order to save copper after WW2. This means you don't have breakers for each branch circuit (there are no branch circuits), just the single mains breaker for the house. This single breaker is too large to trip from a short from occuring in the smaller wires inside an appliance. So each plug (or hardwired device) needs it's own dedicated smaller fuse instead.
- zarzavat 3y ago
  To add: Many pre-90s buildings don’t even have circuit breakers, they have fuse boxes with fuse wire (different fuse to the one being talked about). Literally just a piece of wire that burns out at a certain current and breaks the connection. You “reset” it by putting a new piece of wire in. The second fuse at the plug allows using a narrower gauge of wire in the device’s cord. Let’s say you have a lamp with a 3A fuse, the cord only needs to be able to handle 3A, so then it can be lighter and cheaper. If it had to handle the same amperage as the circuit it’s plugged into then it would be seriously impractical and expensive. Of course there are modern ways of solving this but fuses are dirt cheap and already implemented.
  - outofmyshed 3y ago
    My last place had a 1970s Wylex board, which at least had plug-in MCB modules that replaced the fuse wire holders and can be reset. However given you can still buy fuse wire in DIY stores there still must be installations out there that need it. Shudder.
    - Angostura 3y ago
      I recently replaced the old fusewire plugs with MCB modules. Really didn't fancy trying to wind a bit of wire around the terminals in the cellar in the dark :)
    - Symbiote 3y ago
      My parents' house still has fuses with fuse wire. They had it rewired when they bought it in the 1980s, and that was the standard then. A fuse blowing is so rare I don't think they're worried by the inconvenience. It might happen every 5 years or more.
- deleted 3y ago
  [deleted]
- outofmyshed 3y ago
  Houses built post-1960s (with more than one floor) will have more than one socket ring each protected by a circuit breaker at the distribution board, usually one per floor for general sockets, with a separate one for the kitchen, and usually individual 32A breakers for things like electric ovens and hobs. Lighting rings are also separate, usually on 6A breakers. We cheap out on cable by not running neutrals to the switches, which causes nerds headaches when they want to install generic smart light switches. My house is reasonably large (worked hard, all my own money) and has a 20-way distribution board with separate socket and light rings for groups of rooms. It’s handy for isolation purposes. More recent builds’ rings will be protected by a combination of MCBs and RCDs, or individual RCBOs (now the cost has come down) which combine the two functions and is ultimately the safest option for most situations. Individually fusing plugs (and in the case of high-draw appliances like washing machines and dryers, protecting with a fused socket) is still a very good idea. And don’t get me started on earthing practices in other countries…
  - xattt 3y ago
    Im curious as to why the practice continues. Are any houses built with branch circuits?
zarzavat 3y ago
Let’s say you desperately need a cup of tea. So you buy a cheap 4-way extension cable and 4 electric kettles. You fill all the kettles and turn them on at the same time for maximum tea-making throughput. The combined load of all the kettles exceeds the rating of the extension cable. With a fuse: the fuse in the extension cable plug blows, you buy another fuse, and learn some patience. Without a fuse: the extension cable overheats and causes a fire, your house burns down, and worst of all you still don’t have any tea.
- TheCoelacanth 3y ago
  Without a fuse, the circuit breaker trips and then you go reset it and hopefully learn not to plug in so many kettles next time. You would have to be a maniac to wire up a house without fuses or breakers.
  - oasisaimlessly 3y ago
    From sibling comment: > British household electrical systems are normally built as one large ring circuit, originally in order to save copper after WW2. > This means you don't have breakers for each branch circuit (there are no branch circuits), just the single mains breaker for the house.
    - manarth 3y ago
      In the UK, there's typically one ring circuit and one lighting circuit per storey, a separate ring circuit for the kitchen, and dedicated circuits for large current draws such as an electric oven or hob, shower, or immersion heater. Each circuit would have a dedicated MCB (Miniature Circuit Breaker) which will trip if too much current is drawn. The standard MCB rating for a ring circuit in the UK is 32A.
      - Angostura 3y ago
        Your 6-way extension strip cable has still caught on fire thiugh

British household electrical systems are normally built as one large ring circuit, originally in order to save copper after WW2. This means you don't have breakers for each branch circuit (there are no branch circuits), just the single mains breaker for the house. This single breaker is too large to trip from a short from occuring in the smaller wires inside an appliance. So each plug (or hardwired device) needs it's own dedicated smaller fuse instead.

zarzavat 3y ago
To add: Many pre-90s buildings don’t even have circuit breakers, they have fuse boxes with fuse wire (different fuse to the one being talked about). Literally just a piece of wire that burns out at a certain current and breaks the connection. You “reset” it by putting a new piece of wire in. The second fuse at the plug allows using a narrower gauge of wire in the device’s cord. Let’s say you have a lamp with a 3A fuse, the cord only needs to be able to handle 3A, so then it can be lighter and cheaper. If it had to handle the same amperage as the circuit it’s plugged into then it would be seriously impractical and expensive. Of course there are modern ways of solving this but fuses are dirt cheap and already implemented.
- outofmyshed 3y ago
  My last place had a 1970s Wylex board, which at least had plug-in MCB modules that replaced the fuse wire holders and can be reset. However given you can still buy fuse wire in DIY stores there still must be installations out there that need it. Shudder.
  - Angostura 3y ago
    I recently replaced the old fusewire plugs with MCB modules. Really didn't fancy trying to wind a bit of wire around the terminals in the cellar in the dark :)
  - Symbiote 3y ago
    My parents' house still has fuses with fuse wire. They had it rewired when they bought it in the 1980s, and that was the standard then. A fuse blowing is so rare I don't think they're worried by the inconvenience. It might happen every 5 years or more.
deleted 3y ago
[deleted]
outofmyshed 3y ago
Houses built post-1960s (with more than one floor) will have more than one socket ring each protected by a circuit breaker at the distribution board, usually one per floor for general sockets, with a separate one for the kitchen, and usually individual 32A breakers for things like electric ovens and hobs. Lighting rings are also separate, usually on 6A breakers. We cheap out on cable by not running neutrals to the switches, which causes nerds headaches when they want to install generic smart light switches. My house is reasonably large (worked hard, all my own money) and has a 20-way distribution board with separate socket and light rings for groups of rooms. It’s handy for isolation purposes. More recent builds’ rings will be protected by a combination of MCBs and RCDs, or individual RCBOs (now the cost has come down) which combine the two functions and is ultimately the safest option for most situations. Individually fusing plugs (and in the case of high-draw appliances like washing machines and dryers, protecting with a fused socket) is still a very good idea. And don’t get me started on earthing practices in other countries…
- xattt 3y ago
  Im curious as to why the practice continues. Are any houses built with branch circuits?

zarzavat 3y ago

Let’s say you desperately need a cup of tea. So you buy a cheap 4-way extension cable and 4 electric kettles. You fill all the kettles and turn them on at the same time for maximum tea-making throughput. The combined load of all the kettles exceeds the rating of the extension cable. With a fuse: the fuse in the extension cable plug blows, you buy another fuse, and learn some patience. Without a fuse: the extension cable overheats and causes a fire, your house burns down, and worst of all you still don’t have any tea.

TheCoelacanth 3y ago
Without a fuse, the circuit breaker trips and then you go reset it and hopefully learn not to plug in so many kettles next time. You would have to be a maniac to wire up a house without fuses or breakers.
- oasisaimlessly 3y ago
  From sibling comment: > British household electrical systems are normally built as one large ring circuit, originally in order to save copper after WW2. > This means you don't have breakers for each branch circuit (there are no branch circuits), just the single mains breaker for the house.
  - manarth 3y ago
    In the UK, there's typically one ring circuit and one lighting circuit per storey, a separate ring circuit for the kitchen, and dedicated circuits for large current draws such as an electric oven or hob, shower, or immersion heater. Each circuit would have a dedicated MCB (Miniature Circuit Breaker) which will trip if too much current is drawn. The standard MCB rating for a ring circuit in the UK is 32A.
    - Angostura 3y ago
      Your 6-way extension strip cable has still caught on fire thiugh