Why would you think that?
Fused spur question for 3Kw heater
- Thread starter Mottie
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That sounds like the Dorman & Smith system that was used in some council housing.
https://en.wikipedia.org/wiki/AC_po...ritish_and_related_types#Dorman_&_Smith_(D&S)
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The Rayrolle plug
came in two versions one fused and one not, fused plug with fit in either type socket, non fused would only fit in non fused socket, they were used a lot for 110 volt supplies as could have two fuses one for each phase or line used with 110 seen them used on 240 volt but not sure about fuse in neutral not such a good idea, the larger version had a switch built into socket and you turned plug to switch on and press red button to release.
But many immersion heaters used the old round pin 15 amp plug and socket on a radial either 15 or 16 amp so you could unplug so plumber could fit pre-wired unit but no fuse to get hot, but need a 15 or 16 amp radial or a fused connection unit supplying the socket, could not connect them to a ring final.
So select the biggest black plug you can find, which means greatest surface area to cool it and best colour to radiate heat.
But many immersion heaters used the old round pin 15 amp plug and socket on a radial either 15 or 16 amp so you could unplug so plumber could fit pre-wired unit but no fuse to get hot, but need a 15 or 16 amp radial or a fused connection unit supplying the socket, could not connect them to a ring final.
So select the biggest black plug you can find, which means greatest surface area to cool it and best colour to radiate heat.
In my experience the red plugs are used as a 'Do not remove' sign.
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Often those plugs suffer over-heating where the fuse clips are riveted to the plug's brass pin, but that one appears to have suffered heat damage from the fuse itself.
How exactly can you overload just one leg of a ring, when the ring is fed from two ways?
The regulation which 'dispensates' ring final circuits requires the cable only to have a minimum CCC of 20A.
If a load is right at the middle of a ring, the current will be shared equally between both 'arms' of the ring. However, as one moves the load away from the centre of a ring, then the proportion of the current going through the shorter arm gradually increases (because the impedance of that path is lower), and when one gets very close to one end of the ring, one approaches the situation in which virtually all of the current goes through that shorter arm.
So, if a 32A load were connected very close to one end of the ring, then there could be nearly 12A more going through the 'short arm' than the minimum required CCC of that cable (20A).
In practice, if one has Method C 2.5mm² (CCC=27A), one has to apply an entire 32A extremely close to the end of the ring to get any 'overload', and could never get an appreciable overload (5A being the absolute maximum)
Kind Regards, John
Quite easily.
If a majority of the load is plugged in at one end of the ring, then the current will take the shorter path to and from the consumer unit, due to the higher resistance of the longer leg. Standard practise is to consider how ring circuit might be loaded and lay it out to distribute the potential load as evenly as possible.
One way, where the ring circuit is all in a straight line along a wall, is to use 'alternate wiring' for sockets. Call the two runs out and back A and B, first socket along the wall connected to A, second socket connected to B, followed by A then B all the way to the far end.
Do you see any advantage in that method over having a radial circuit?
Certainly it does not save copper
I'm not really sure how that would help anything. It remains the case that the theoretical risk of somewhat 'overloading' one arm of the ring will exist if something approaching 32A worth of loads is connected to sockets close (electrically) to one end of the ring, and that is regardless of where the sockets are physically located.
Indeed, if someone wanted to avoid that theoretical/hypothetical risk by avoiding plugging several large loads into sockets which were (electrically) close to one end of the ring, what you suggest would make life more difficult for them, because they could not so easily deduce which of the sockets were (electrically) close to (the same) one end of the ring!
Kind Regards, John.
Where things need to be plugged in, is where things need to be plugged it - usually there is little choice as to which socket to use and certainly never considered by a user.
The other way to wire a long straight run of sockets on a wall, would be for each socket to be wired in turn, with the final socket at the far end - having a long run back to the consumer unit. Are you suggesting that might be a better way of laying out the circuit John?
it's a good point.
We would seem to be discussing a ring circuit.
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