Dedicated mains supply - what fuse?

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You need to wire such a circuit in accordance with current UK wiring regulations and fuse it also as required. There seems to be little info on line (except about the colour changes) but lots of referals to the 16th IEE Wiring Regulations Explained (available from bookstores).
 
I think circuit breakers don't have different impedance like fuses, so there's nothing to be gained by going for a high current one. Just work out the max continuous current you are ever likely to see and then pick the next one above that.

To be honest the equipment connected should - will - have correct fuses in place anyway so these will always blow first. The breaker is to protect the wiring installation and as a last ditch 'fuse' in the event of stupidity.
 
Indeed the breaker is there to protect the wiring (and hence your house from burning down!). There are instances where things like dimmer loads can induce strange behaviours into breakers, but as long as your load is clean, then there should be no particular problem there.

Your plug fuses will in turn protect the wiring to your equipment (assuming you've wired them on the conventional 30Amp ring main and are using the conventional 13Amp plugs). I've known people to still use the old smaller 5 Amp and the almost miniature 2 Amp plugs for things like audio equipment because of the relative huge size of the 13 Amp fused plug. If you are using the 5 Amp or 2 Amp plugs, because of the lack of plug fusing, the circuit should be fused to a maximum of 2 or 5 Amps respectively. On common approach is to run these on a fused spur from a ring main, and fused again at 5 or 2 Amps depending on the plugs.
 
Hi Nuuk,
I don't have the tables for current rating of two core +earth but Imax will be in the region of 16A to 20A.
Your MCB/fuse must be less than the cable rating.
It looks like you cannot go above 15A for fusing.
That still allows upto 3.3kW if you avoid switch on surges.
 
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