Ring vs Radial circuit, what would you do?
- Thread starter dsbuds
- Start date
As I said, the nature of an MCB is such that it cannot really be 'overloaded', since it automatically protects itself from 'over-currents'.
I would ay that I am thinking (about what your wrote), not 'over-thinking'.
That seems sensible in the sense of not favouring the connection of what would otherwise be two or more multi-socket radials (or even ring finals) to the same MCB/RCBO, the only real historical 'excuse' for doing that being an inadequate number of 'ways' in the fuse box or CU.
However, in some other situations it seems reasonable to have more than one cable originating at nee MCB/RCBO. Indeed, Appendix 15 of BS7671 acknowledges that 'spurs' may originate at the MCB of both ring and radial sockets circuits. It can also be convenient for lighting circuits which serve lights in two or more different directions from the CU (the alternative being unnecessary use of more cable and/or JBs).
Even two ring finals originating from the same MCB/RCBO is theoretically acceptable (provided the device terminals will accommodate four conductors, but I doubt there would often be a reason for even considering that.
As with so many things, I think the need is for common sense, rather than 'strict rules'
You can be such a dick
IF the MCB is protecting the load of multiple sockets on 3 cables then the chance of the MCB being “over loaded” is quite high - which of course means it should turn itself off resulting in inconvenience for the home owner
Rude response to a quote perfectly acceptable circuit which is blatanlty obviously impossible to suffer any overload damage as long as the MCB is functioning correctly and of a sufficiently high breaking current.
Which means it's functioning as an over current protection device just as it's designed.
I see! In fact, my middle name is Richard, so I suppose you're actually right.
That is not 'overloading an MCB'. You seem to be assuming that having more than one cable originating from an MCB/RCBO increases the chances of loads resulting in a total current which is in excess of the In of the OPD, but it really isn't as simple as that, since, with a sockets circuit, a designer has virtually no control over 'what gets plugged in where'.
What, I wonder, does an 'average sockets circuit' look like? I would think that, say, 8 double sockets would not be at all unusual. If one takes that figure, that means that with just one cable connected to the CU, there could, hypothetically, be 208 A worth of loads plug into sockets on a circuit protected by a 32 A, 20 A or even 16A OPD.
Probably more to the point, if one added a second (and maybe even a third) cable to the MCB/OPD which supplied a new set of 8 double sockets, the user would not suddenly increase his/her usage of electricity, so the current through the OPD would be exactly the same with two or three cables connected to it as if there were only one cable.
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