My gob is truly smacked. I would never do this. It goes against everything thing I have been taught.
Single wall socket connected to two Mini Circuit Breakers.
- Thread starter Daniel Keenan
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What, you mean selecting conductors that have sufficient CCC rather than fusing down?
It's only a combination of a 32amp 2.5mm2 ring, and a 32amp 4.0mm2 radial.
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Yes, it has.
Look at it another way.
It is explicitly stated that a spur may be taken from a point on the ring or the MCB.
You want a double socket under the CU so you run the usual 2.5mm² from the MCB to the socket - perfectly acceptable and normal.
What would you do if you wanted two double sockets (or five) under the CU?
It is explicitly stated that a spur may be taken from a point on the ring or the MCB.
You want a double socket under the CU so you run the usual 2.5mm² from the MCB to the socket - perfectly acceptable and normal.
What would you do if you wanted two double sockets (or five) under the CU?
New circuit, 4mm radial on its own breaker,
Or Extend existing 2.5mm ring to encompass new sockets.
Or Extend existing 2.5mm ring to encompass new sockets.
Ok, and the difference between that and adding to ring MCB is what?
Electrically nothing. But it goes against the whole ethos of a ring final: a distributed circuit with current-limited connections. Every connection is limited to 13A, except for a double socket where the max could be 26A.
Your arrangement could allow a current load limited only by the 32A MCB, and for this to be at one point in the ring.
Your arrangement could allow a current load limited only by the 32A MCB, and for this to be at one point in the ring.
Ok.
I don't think that is the reason for 13A fuses in plugs.
So what?
Your additional sockets on the ring under the CU would be so close together and so close to one end to make no difference to that and I have said the spur should not be too close to one end.
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That's the point, isn't it?
Wherever on the ring it is, only one cable is needed; one that can handle 32A.
Wherever on the ring it is, only one cable is needed; one that can handle 32A.
I realise that. I was doing the same. 
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Wow you guys are just unending fountains of knowledge. Thank you so much. Couple of questions tho.
1. Why would you put a consumer unit on the end or is Taylor making a sarcastic joke?
I dont know what CCC stands for? Google says it stands for China Compulsory Certificate. What I think you're saying is creating a spur with the 4mm wire instead of what Taylor would do which is use a 2.5mm wire and "fuse down" with a fuse that prevents more than 13.5 amp from crossing. Not sure how you achieve that without melting the fuse. Wouldn't a resistor be better? Please clarify "fuse down" as i'm just getting myself into a state of con'fuse'ion
2. I really dont get what Spark means by "Directly" and "ie not a spur" isnt the whole definition of a spur to directly connect to a circuit (in this case final ring) whether it be from the socket or by cutting the ring, wiring in a junction box and creating a spur off that?
I understand what Taylor means by the max draw will be 26amps on the circuit at a double socket as the fuses within each consumer device are 13amps or less. Two consumer devices = 13 x 2. Ring finals are designed to accommodate this much current/amps even if only one "side" of the ring is connected to the socket/double socket. 2mm wire is rated up to 26amps
What i think Taylor is saying here is that if the 4mm wire draws just under 32amps then that would be bad. For the life of me I cant work out how the 4mm wire connected to a 2 gang socket would do this unless the device pulling from the socket is using a 35 amp fuse and is pulling 31.9amps. Even so, as as EFL said earlier the 2.5mm wires will distribute the load even if its over 26amps (for example the 4mm spur is pulling a 31.9amp load) if the spur is placed reasonably in the middle of the ring circuit.
In my mind the only potential issues I can see with doing this is if the ring circuit is massively extended, so the 4mm spur goes from being relatively in the middle to RELATIVELY too close to the CU. Which seems improbable to an ignorant bloke like me but i guess you could build an extension 3 times the size of your original house you could create too much resistance on one side of the ring (due to the amount of new cabling and plugs) and create this problem...
The other issue is that the ring circuit has a breakage and then only one 2.5mm wire is supplying the 31.9amp to the 4mm wire. This could overload the single, intact 2.5mm that's still connected to the consumer unit without tripping the aforementioned 32amp MCB. Of course this point is mute as the damn circuits gonna overload (if one of the original ring sockets then starts pulling 31.9amps) regardless of whether or not its got a 4mm spur due to the inherent flaw of ring circuits.
1. Why would you put a consumer unit on the end or is Taylor making a sarcastic joke?
I dont know what CCC stands for? Google says it stands for China Compulsory Certificate. What I think you're saying is creating a spur with the 4mm wire instead of what Taylor would do which is use a 2.5mm wire and "fuse down" with a fuse that prevents more than 13.5 amp from crossing. Not sure how you achieve that without melting the fuse. Wouldn't a resistor be better? Please clarify "fuse down" as i'm just getting myself into a state of con'fuse'ion
2. I really dont get what Spark means by "Directly" and "ie not a spur" isnt the whole definition of a spur to directly connect to a circuit (in this case final ring) whether it be from the socket or by cutting the ring, wiring in a junction box and creating a spur off that?
I understand what Taylor means by the max draw will be 26amps on the circuit at a double socket as the fuses within each consumer device are 13amps or less. Two consumer devices = 13 x 2. Ring finals are designed to accommodate this much current/amps even if only one "side" of the ring is connected to the socket/double socket. 2mm wire is rated up to 26amps
What i think Taylor is saying here is that if the 4mm wire draws just under 32amps then that would be bad. For the life of me I cant work out how the 4mm wire connected to a 2 gang socket would do this unless the device pulling from the socket is using a 35 amp fuse and is pulling 31.9amps. Even so, as as EFL said earlier the 2.5mm wires will distribute the load even if its over 26amps (for example the 4mm spur is pulling a 31.9amp load) if the spur is placed reasonably in the middle of the ring circuit.
In my mind the only potential issues I can see with doing this is if the ring circuit is massively extended, so the 4mm spur goes from being relatively in the middle to RELATIVELY too close to the CU. Which seems improbable to an ignorant bloke like me but i guess you could build an extension 3 times the size of your original house you could create too much resistance on one side of the ring (due to the amount of new cabling and plugs) and create this problem...
The other issue is that the ring circuit has a breakage and then only one 2.5mm wire is supplying the 31.9amp to the 4mm wire. This could overload the single, intact 2.5mm that's still connected to the consumer unit without tripping the aforementioned 32amp MCB. Of course this point is mute as the damn circuits gonna overload (if one of the original ring sockets then starts pulling 31.9amps) regardless of whether or not its got a 4mm spur due to the inherent flaw of ring circuits.
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