OK, thanks for your help - I misunderstood you statement "With a 50A supply to the building, you do need to do some corrective work." - I thought you meant there was an issue with the 50A feed, apologies for the confusion.
Found 1.5mm wire in my ring :(
- Thread starter icarusbop
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This post superseded but I can't find how to delete it
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Some of the 2.5mm sockets are running through a kitchen space, microwave, oven fridge. (Hob is on a separate feed) so I think this needs to be kept as a ring if possible with 2.5.
So this might be a good solution- I could split the ring into two halves, the side with 1.5mm can have a 16a MCB. With the current infrastructure it would end up with 1 x twin socket on 2.5, after which 2 x twin sockets on the 1.5. (low load sockets, in all probability lamps, phone, chargers, perhaps the odd laptop)
The other half I could run a new 2.5mm back to the CU (there is a relatively easy route for this), and make it into a 32A ring to carry the rest of the sockets including the kitchen appliances.
Is this plan allowed/acceptable?
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I see. More of a house, than an outbuilding. (I was thinking it was more of a shed/summer house)
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Ring Final Circuit is for running mains sockets in such as a house and if twin and earth then a 30 or 32 amps protective device (eg a fuse or a breaker) .
Ring Mains are sometimes found in the streets to reduce volts drop at lots of places.
Another type of Ring Main can sometimes be found at generation/distribution points - as an example lets say you have 10 generators supplying power to users then each cable on that ring can take the full load of all but has isolators on every leg position on that ring. That means if you switch off and lock off two isolators you can safely work on/replace one generator (or any number of adjacent generators) and the remainder are still running power to the remainder of the ring which has now become two radial legs effectively. They might not be actual generators themselves but might actually be transformers powered from another source.
From what you have described the best answer might be to replace with 2/5 T & E but if impossible then either disconnect the whole circuit.
It might or might not be permissible to substitute for a 20A MCB or a 16A MCB or a 10A MCB or a 6A MCB to make it safe but would that new setup still keep the circuit mostly usable?
Ring Mains are sometimes found in the streets to reduce volts drop at lots of places.
Another type of Ring Main can sometimes be found at generation/distribution points - as an example lets say you have 10 generators supplying power to users then each cable on that ring can take the full load of all but has isolators on every leg position on that ring. That means if you switch off and lock off two isolators you can safely work on/replace one generator (or any number of adjacent generators) and the remainder are still running power to the remainder of the ring which has now become two radial legs effectively. They might not be actual generators themselves but might actually be transformers powered from another source.
From what you have described the best answer might be to replace with 2/5 T & E but if impossible then either disconnect the whole circuit.
It might or might not be permissible to substitute for a 20A MCB or a 16A MCB or a 10A MCB or a 6A MCB to make it safe but would that new setup still keep the circuit mostly usable?
For 19 years it has been a granny annexe. Granny no longer needs it, so I'm reworking it into 2 bedsits with shared lounge, kitchen and wetroom.
I've added 2 x partition walls which contain new wiring and ring. But I've only just discovered the issue with the old ring.
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Hello, I made a diagram of the wiring. Colours and thickness are used to portray old/new cabling and difference between 2.5mm and 1.5mm.
Thanks.
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Replacing two of the lengths is proving to be difficult without a lot of collateral damage.
Current best suggestion from AndyPRK I think is to convert to a 16a spur for the thin wires I cant replace, and add a new return to make the rest of it a proper 2.5mm ring.
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I ring main is used to allow any section to be isolated to work on it, found mainly with HV supplies, and the cable can take the whole load, the ring final invented near the end of second world war allows the use of a smaller cable so uses less copper, I can't remember the size think it was 7/0.029 which was larger than 2.5 mm² when we went metric we were allowed to used 2.5 mm² for most cables, but 1.5 mm² with mineral insulated cables.
With 2.5 mm² we were allowed to use up to 85 meters, but this changed when the permitted volt drop was changed from 4% to 5% for socket outlets, so now 106 meters. Although the way this is worked out is not in the regulations, so is open to some debate, it is assumed 20 amp centre of the ring and 12 amp even spread, we do have a directive that non-portable items over 2 kW should be on a dedicated circuit, but except for the immersion heater no one seems to worry about that.
For you, best option seems a 20 amp MCB,
With 2.5 mm² we were allowed to use up to 85 meters, but this changed when the permitted volt drop was changed from 4% to 5% for socket outlets, so now 106 meters. Although the way this is worked out is not in the regulations, so is open to some debate, it is assumed 20 amp centre of the ring and 12 amp even spread, we do have a directive that non-portable items over 2 kW should be on a dedicated circuit, but except for the immersion heater no one seems to worry about that.
For you, best option seems a 20 amp MCB,
Thanks for the suggestion, I think it would work.
However, I reassessed last night, apparently there are 2 spare ways so I no longer have a need to retain the spare way.
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