British vs American wiring scheme

Eric, there is a ring from the main breaker box that goes round the area to be wired and returns to the same point. This ring usually wired for an area like upstairs, downstairs and kitchen has it's own breaker rated at 30 amps [ remember we are on 240 volts here ] Around that ring are placed the sockets, usually switched twins.

Then each appliance has a 3 pin plug, live, neutral and ground going to the appliance. This plug carries it's own internal fuse rated for the appliance.

The advantages are everything in the UK is completely portable and can go onto any circuit in any house because of this fuse. You can have a small electrical soldering iron rated at 1 amp alongside a stick welder rated at 13 amp running off the same twin socket and both are fully protected.

John S.

Just to expand on that since John seems to have missed your point. We have a 'consumer unit' which has the main incoming breaker which is normally earth leakage, and then we have an array of lower current breakers depending on the size of house. Small houses will have a power 'ring' as Johndescribes for the upstairs, a separate ring for the down stairs, and separate feeds to the cooker and/or electric heater for shower. The lighting circuits will be separate for each floor with a 5amp breaker.

Just like the US, heavy loads have their own breaker and feed from the consumer unit, and in some places there may be additional earth leakage breakers with a lower trip current than the main breaker plugged into sockets on the power ring. I have them for the water feature pumps outside.

I also run a separate ring for the garage with it's own earth leakage breaker, so when I c*ck up, the house does not go out :)

Yes, that's pretty much it. We call our system a 'Ring' main and the system which was very similar to yours which we used to use a 'Spur' system. We never used a 2 phase of split phase system in a domestic environment. I'm not entirely sure why we went to the ring system, mainly I'm told because it enables wire of half the nominally required size to be used because it is 'fed' from both ends. I actually think it is a rather poor way of wiring as you don't know if there is a fault when you could be getting supply from only one end not two. Of course if you use an expensive electrician that couldn't possible happen........

Nothing else, either industrial or electronic is wired this way for just that reason among others.

Richard

Richard, Industry still use ring mains for single phase working, IE workshop benches etc. Machines are not wired this way as they are single load appliances and never move.

John S.

We use a 'ring' because the voltage is constant at any point...... more or less..... and is independent of any load around the ring. If you have a single ended system, and place a heavy load at the end, then the voltage drop through the cable is reflected all the way up the spur.You don't get this with a ring.

I was a little careless with my phrasing, by 'nothing else..... ' I was really thinking about machines and appliances. Even a complicated machine or machine tool wouldn't have a ring main within it even though it may have plenty of distribution around it - a backbone and spurs, but I not seen a ring. That said a machine would have a heap of different sizes of cable according to the loading to ensure the regulation wasn't excessive. That's not the sort of decision authorities like to entrust to a sparky doing domestic work. Big for sockets, small for lights is about as far as they dare go.

Richard

Thanks to everyone who posted replies to my wiring question. It's another example of how there are many ways to a solution. Chers, Eric

It was developed for the post-war rebuild of UK with the aim of using the minimum amount of (imported) copper. You surely don't want to return to the pre-war BS646 stuff.

Local substations are fed from an 11kV ring main and London is supplied at 400kV by a mostly underground ring main. The rings run open, the advantage is that when the JCB digs up the cable, the supply can be restored by switching round the open circuit to the failed section. This explains a common feature of some power cuts. Supply off for half an hour (engineer driving to substations to isolate) then on, perhaps allmost immediate off again. (He couldn't find the black JCB, so its trial and error - oops. picked wrong) ten minute off (drive to next substation) then on, repeat till job done. In these circuits there may be little saving of copper as the cables are fault level rated.

Regards,

David P.