That should be supplied by fire resistant cabling from the origin, on it's own dedicated circuit.
Isolator on Ring circuit
- Thread starter 333rocky333
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Them switches then go on to feed Bs1363 accesories, I believe, as the reg is in the section about overload current, that what there saying is other stuff connected to a 32a Ring, MAY need larger conducters than 2.5mm, whereas with Bs1363 appliances its assumed 20 amp load therefore a minimum of 2.5mm can be used.
I'm not at all sure that is how 'they' think/thought about it (if they thought very much at all!).
As you say, it's in the section about overload current. I think that all it's really saying in that, because its a ring (with the load hopefully reasonably distributed around it), it is permissible to have a cable with a CCC as low as 20A (at least 2.5mm² T+E or 1.5mm² MICC) protected by a 32A OPD - which otherwise would not be allowed by that section of the regs.
The reg allows a double socket to be installed on the ring with another double socket taken from it as an unfused spur. In theory, that means that there could be a load of 52A (some would say 40A) applied at that 'one point' on the ring, despite the fact that only BS1363 accessories are involved - and, of course, one could have 10 or 20 (BS1363) double sockets installed on the ring (which could multiply up to a theoretical 260A or 520A
). I therefore don't think that restricting a ring to BS1363 accessories does anything to limit the potential overload of the cables.Kind Regards, John
I have always assumed that the minimum of 2.5mm² T&E is because the regulation (still) includes a BS3036 fuse being the OPD. This in itself is somewhat poor way of writing a regulation. Were this not the case then 1.5mm² T&E (method C, of course) would meet the requirement for the 20A CCC.
If that is the case, then a ring with a 32A MCB as the OPD could be adequately wired in 1.5mm². If so, there would be no need for a minimum of 2.5mm² therefore thinking there are other reasons for it in other places such as spurs might be mistaken.
If that is the case, then a ring with a 32A MCB as the OPD could be adequately wired in 1.5mm². If so, there would be no need for a minimum of 2.5mm² therefore thinking there are other reasons for it in other places such as spurs might be mistaken.
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Agreed. I presume that when the reg was written (and hasn't changed all that much since), fuses were the norm. Somewhere along the line it really should have been updated to make a distinction between MCBs and BS3036s - in which case, as you say, 1.5mm² (Method C) 32A ring finals ought to be allowed when the OPD is an MCB.
Having said that, people seem to be (seemingly irrationally) 'nervous' about 1.5mm² (maybe wanting the comfort of an additional 'safety margin') - since I don't recall having heard much, if anything, about 1.5mm² (Method C) 20A radials - which should be fully 'compliant'.
Kind Regards, John
What is that current rating please, what table is that you are using
4D5
20A - Table 4D5 (is 19.5A in 4D2A).
4D5 the table which also had to be modified to make Method A 2.5mm OK for ring finals (it was/is 18.5A in 4D2A)
Kind Regards, John
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