5 ms·

I'm struggling to understand how the British grid works, as an Italian transplated to UK. IIRC in Italy most residential circuit breakers have a limit of 3.3 kW

by sph 3y ago

I'm struggling to understand how the British grid works, as an Italian transplated to UK. IIRC in Italy most residential circuit breakers have a limit of 3.3 kW, so it's pretty easy to trip it with a few appliances running, and we don't even use electric kettles that much. Yet in Britain, with a 3 kW kettle, I've never managed to trip it, with a combination of laundry machine, electric oven, microwave, dishwasher. Is there no circuit breaker limit?

jonatron 3y ago
We have ring circuits, which are typically on 32A breakers.
- sph 3y ago
  3000 W / 230 V = ~13A, does this mean I could run two 3kW kettles and still have 1.3kW spare before everything shuts down? That's massive.
- iso1631 3y ago
  And it's great, until the ring is broken. If a ring becomes disconnected, you then have a single 4mm circuit rated at 18A carrying 30A.
mytailorisrich 3y ago
There may be several circuits, and they all have independent breakers. Certainly, an electric cooker/oven will be on its own circuit as it has higher requirements. Then, standard ring circuit is 32A, and individual sockets are limited to 13A (via fuse in plug). So you will need to have 2 kettles on on the same circuit and then add a third device pulling not an insignificant amount of power (32 - 2x13 = 6A) before the breaker trips. This will be safe if the ring circuit is not faulty as they are usually wired with two 2.5mm2 cables (two because it's a ring) that have a standard rating of 24A each...
- sph 3y ago
  Thanks, that's incredible. I won't have to worry about tripping the circuit breaker anymore.
- housemusicfan 3y ago
  UK electrics are mad - with the ring main and what not requiring fuses in the enormous plugs. All vestiges of post-WWII design. By code a modern American kitchen must have: - dedicated 50A 240V for an electric stove or oven (unless gas service is present) - dedicated 20A 120V each for the fridge, microwave, dishwasher, disposal (the latter being uncommon outside the US and Canada). The last two often share a circuit. - two 20A countertop circuits with GFCI protection (what the Brits call 'RCD' - the difference being ours trip at 5mA vs 30mA and won't knock out half the house.)
  - iso1631 3y ago
    You assert that it's mad but then describe a mad situation in the US. A typical British kitchen will have a ton of sockets (although never enough), to plug in a fridge (or two, or three), a microwave (or several - they rarely goes about 1kW anyway), a dishwasher, a washing machine, a tumble dryer (UK kitchens tend to have washers and dryers, rather than bathrooms. Larger houses have separate utility rooms) The only thing on a dedicated circuit would be a hard-wired oven.
    - housemusicfan 3y ago
      Thinking that having dedicated independent circuits is madness sounds like Stockholm syndrome. The point being a single faulty appliance won't knock out the lights and sockets to half the house simultaneously (a common occurrence during a fault in the UK, especially the RCD). It's also quite convenient to switch off a single appliance for service. Yes British sockets are all switched but not necessarily in a convenient location. A software analogy would be running all your services on separate VMs, as opposed to running them all on a single server which could go down at once. Brits don't even put outlets in the bathroom, minus a current-limited transformer-isolated one for an electric razor.
mananaysiempre 3y ago
> in Italy most residential circuit breakers have a limit of 3.3 kW Wait, really? That’s seriously underpowered, though I guess if you never need electric stoves or heating it could be somewhat usable. An ex-Soviet big-city apartment building will usually support 40A (~9kW) per apartment, and in France I had the impression that the values were similar—except for student dorms, which are supplied and wired like apartment buildings despite the density of occupants being 3x that or more, because apparently the builders could not into engineering and the uni authorities find it easier to blame the occupants (yes, I’m still a bit salty about that).
- sph 3y ago
  I haven't lived in Italy for 10+ years, so I don't know if anything has changed since, but that was the limit for all houses I've lived in, and from a quick Google search, it depends on your contract — the lowest is a 2 kW limit, 3.3 kW is the most common, and you can ask for an increase for an additional monthly fee. Heating and stoves are usually gas-powered, we don't do electric except for water boilers. I have always wondered if those limits and the high electricity costs are because Italy abolished nuclear energy post-Chernobyl, doesn't have a massive oil and gas operation, so most of it is imported at a premium.
- N19PEDL2 3y ago
  > Wait, really? We should thank whoever came up with the idea of abolishing nuclear power in Italy. What a big mistake! > if you never need electric stoves or heating it could be somewhat usable Heating and stoves in Italy are usually gas-powered. Ovens and kettles are electric but normally do not exceed 3.3 kW, however, we need to be careful not to use too many high-consumption appliances together (e.g., oven and washing machine). The introduction of increasingly restrictive energy classes for electric appliances in recent years has mitigated the problem to some extent anyway.
  - pjc50 3y ago
    Italy has almost the same per-capita electricity consumption as the UK. I suspect any residential limitations are made up by industrial and transport usages. You guys really need to get on the solar panels, though.
sbuk 3y ago
When when the UK was rebuilding the housing stock post WW2, ring mains (or circuits) were designed to both increase consumer safety and to combat the anticipated post-war copper shortage. This design allows for high integrity earthing and greater power per unit of floor area for a given cable size than a radial circuit. Most white goods (Dishwashers, washing machines, etc.) are locally fused and often ovens are on a separate ring with their own fuses in the distribution board. This is why you rarely trip the circuit. It can be done though.
MisterTea 3y ago
Going from memory but this is an artifact of WW2. There was a copper shortage so they decided to save on wiring costs by running only a few high current circuits through the whole house. The appliance plugs are instead fused as any fault in the appliance would happen after the plug. This is why UK plugs are all fused - they are the final branch circuit over current protection device. I actually like the idea.
dotancohen 3y ago
> I'm struggling to understand how the British grid works Like most things, understanding the history helps. The ring circuit was designed because it uses less copper than other methods - and copper was scarce after WWII. Almost all other design decisions either come directly from the idea of saving copper, or the idea that there are not enough Legos to step on so the electric plug must substitute.
rickboyce 3y ago
If you want a deep dive this video made by a British electrician is worth a watch https://youtu.be/hZN6hiGLtrE https://youtu.be/hZN6hiGLtrE In a perfect world a ring circuit is a clever invention - it offers a circuit that can safely deliver about 7.3kW with hardly any more copper than normally could deliver about 4.6kW. However in practice they have a hidden failure mode - if you break the ring they will carry on working apparently without problem except it’s quite possible that you now have overheating cables in a wall somewhere. In the real world houses are full of changes (both DIY and professional) that inadvertently break the ring and it’s not at all uncommon to see in a house with even modest refurb works having been done.
laurencerowe 3y ago
That sounds almost as bad as what we have to deal with in the US! I live in an early 20th century apartment in San Francisco and I quickly learned not to run my 1.8kW kettle at the same time as my 1.2kW microwave as it would consistently trip the power. More annoying is when the fridge compressor motor starts up while running either as that also trips the power.
- unethical_ban 3y ago
  I just moved from a place where, if I ground my beans and then turned on the kettle or toaster, I could hear the motor slow down.
dfawcus 3y ago
Post WW2 for newly built small flats, ring mains were designed to save on copper (as it was in shortage). The intention was to allow for 3-bar electric fires to be operated as 13A loads, and be moveable between rooms. Rings are more complex to test, and have nasty failure modes. I'd argue that they should only be used in said small flats, and that 20A bus/radial runs should be used in larger builds. i.e. any modern house, rather than a flat. Said run the supplying all of the sockets in any given room, it does though require a larger "consumer unit". The rings have a 30A (or now 32A) at the "consumer unit" (distribution fuse box) with two cables running in a loop around all sockets in the circuit. The cables have traditionally been 2.5mm, and open clipped, so rated at around 27A (based upon preventing overheating). Hence when operating properly, the wiring in the circuit can carry 54A, the circuit is fused at 30A (or 32A) to protect the cable, and an individual load is limited to 13A (being the highest cartridge fuse commonly available). Have a look here: https://www.diydoctor.org.uk/projects/cablesizes.htm https://www.diydoctor.org.uk/projects/cablesizes.htm

by sph 3y ago

jonatron 3y ago

We have ring circuits, which are typically on 32A breakers.

sph 3y ago
3000 W / 230 V = ~13A, does this mean I could run two 3kW kettles and still have 1.3kW spare before everything shuts down? That's massive.
iso1631 3y ago
And it's great, until the ring is broken. If a ring becomes disconnected, you then have a single 4mm circuit rated at 18A carrying 30A.

mytailorisrich 3y ago

There may be several circuits, and they all have independent breakers. Certainly, an electric cooker/oven will be on its own circuit as it has higher requirements. Then, standard ring circuit is 32A, and individual sockets are limited to 13A (via fuse in plug). So you will need to have 2 kettles on on the same circuit and then add a third device pulling not an insignificant amount of power (32 - 2x13 = 6A) before the breaker trips. This will be safe if the ring circuit is not faulty as they are usually wired with two 2.5mm2 cables (two because it's a ring) that have a standard rating of 24A each...

sph 3y ago
Thanks, that's incredible. I won't have to worry about tripping the circuit breaker anymore.
housemusicfan 3y ago
UK electrics are mad - with the ring main and what not requiring fuses in the enormous plugs. All vestiges of post-WWII design. By code a modern American kitchen must have: - dedicated 50A 240V for an electric stove or oven (unless gas service is present) - dedicated 20A 120V each for the fridge, microwave, dishwasher, disposal (the latter being uncommon outside the US and Canada). The last two often share a circuit. - two 20A countertop circuits with GFCI protection (what the Brits call 'RCD' - the difference being ours trip at 5mA vs 30mA and won't knock out half the house.)
- iso1631 3y ago
  You assert that it's mad but then describe a mad situation in the US. A typical British kitchen will have a ton of sockets (although never enough), to plug in a fridge (or two, or three), a microwave (or several - they rarely goes about 1kW anyway), a dishwasher, a washing machine, a tumble dryer (UK kitchens tend to have washers and dryers, rather than bathrooms. Larger houses have separate utility rooms) The only thing on a dedicated circuit would be a hard-wired oven.
  - housemusicfan 3y ago
    Thinking that having dedicated independent circuits is madness sounds like Stockholm syndrome. The point being a single faulty appliance won't knock out the lights and sockets to half the house simultaneously (a common occurrence during a fault in the UK, especially the RCD). It's also quite convenient to switch off a single appliance for service. Yes British sockets are all switched but not necessarily in a convenient location. A software analogy would be running all your services on separate VMs, as opposed to running them all on a single server which could go down at once. Brits don't even put outlets in the bathroom, minus a current-limited transformer-isolated one for an electric razor.

mananaysiempre 3y ago

> in Italy most residential circuit breakers have a limit of 3.3 kW Wait, really? That’s seriously underpowered, though I guess if you never need electric stoves or heating it could be somewhat usable. An ex-Soviet big-city apartment building will usually support 40A (~9kW) per apartment, and in France I had the impression that the values were similar—except for student dorms, which are supplied and wired like apartment buildings despite the density of occupants being 3x that or more, because apparently the builders could not into engineering and the uni authorities find it easier to blame the occupants (yes, I’m still a bit salty about that).

sph 3y ago
I haven't lived in Italy for 10+ years, so I don't know if anything has changed since, but that was the limit for all houses I've lived in, and from a quick Google search, it depends on your contract — the lowest is a 2 kW limit, 3.3 kW is the most common, and you can ask for an increase for an additional monthly fee. Heating and stoves are usually gas-powered, we don't do electric except for water boilers. I have always wondered if those limits and the high electricity costs are because Italy abolished nuclear energy post-Chernobyl, doesn't have a massive oil and gas operation, so most of it is imported at a premium.
N19PEDL2 3y ago
> Wait, really? We should thank whoever came up with the idea of abolishing nuclear power in Italy. What a big mistake! > if you never need electric stoves or heating it could be somewhat usable Heating and stoves in Italy are usually gas-powered. Ovens and kettles are electric but normally do not exceed 3.3 kW, however, we need to be careful not to use too many high-consumption appliances together (e.g., oven and washing machine). The introduction of increasingly restrictive energy classes for electric appliances in recent years has mitigated the problem to some extent anyway.
- pjc50 3y ago
  Italy has almost the same per-capita electricity consumption as the UK. I suspect any residential limitations are made up by industrial and transport usages. You guys really need to get on the solar panels, though.

sbuk 3y ago

When when the UK was rebuilding the housing stock post WW2, ring mains (or circuits) were designed to both increase consumer safety and to combat the anticipated post-war copper shortage. This design allows for high integrity earthing and greater power per unit of floor area for a given cable size than a radial circuit. Most white goods (Dishwashers, washing machines, etc.) are locally fused and often ovens are on a separate ring with their own fuses in the distribution board. This is why you rarely trip the circuit. It can be done though.

MisterTea 3y ago

Going from memory but this is an artifact of WW2. There was a copper shortage so they decided to save on wiring costs by running only a few high current circuits through the whole house. The appliance plugs are instead fused as any fault in the appliance would happen after the plug. This is why UK plugs are all fused - they are the final branch circuit over current protection device. I actually like the idea.

dotancohen 3y ago

> I'm struggling to understand how the British grid works Like most things, understanding the history helps. The ring circuit was designed because it uses less copper than other methods - and copper was scarce after WWII. Almost all other design decisions either come directly from the idea of saving copper, or the idea that there are not enough Legos to step on so the electric plug must substitute.

rickboyce 3y ago

If you want a deep dive this video made by a British electrician is worth a watch https://youtu.be/hZN6hiGLtrE https://youtu.be/hZN6hiGLtrE In a perfect world a ring circuit is a clever invention - it offers a circuit that can safely deliver about 7.3kW with hardly any more copper than normally could deliver about 4.6kW. However in practice they have a hidden failure mode - if you break the ring they will carry on working apparently without problem except it’s quite possible that you now have overheating cables in a wall somewhere. In the real world houses are full of changes (both DIY and professional) that inadvertently break the ring and it’s not at all uncommon to see in a house with even modest refurb works having been done.

laurencerowe 3y ago

That sounds almost as bad as what we have to deal with in the US! I live in an early 20th century apartment in San Francisco and I quickly learned not to run my 1.8kW kettle at the same time as my 1.2kW microwave as it would consistently trip the power. More annoying is when the fridge compressor motor starts up while running either as that also trips the power.

unethical_ban 3y ago
I just moved from a place where, if I ground my beans and then turned on the kettle or toaster, I could hear the motor slow down.

dfawcus 3y ago

Post WW2 for newly built small flats, ring mains were designed to save on copper (as it was in shortage). The intention was to allow for 3-bar electric fires to be operated as 13A loads, and be moveable between rooms. Rings are more complex to test, and have nasty failure modes. I'd argue that they should only be used in said small flats, and that 20A bus/radial runs should be used in larger builds. i.e. any modern house, rather than a flat. Said run the supplying all of the sockets in any given room, it does though require a larger "consumer unit". The rings have a 30A (or now 32A) at the "consumer unit" (distribution fuse box) with two cables running in a loop around all sockets in the circuit. The cables have traditionally been 2.5mm, and open clipped, so rated at around 27A (based upon preventing overheating). Hence when operating properly, the wiring in the circuit can carry 54A, the circuit is fused at 30A (or 32A) to protect the cable, and an individual load is limited to 13A (being the highest cartridge fuse commonly available). Have a look here: https://www.diydoctor.org.uk/projects/cablesizes.htm https://www.diydoctor.org.uk/projects/cablesizes.htm