Dedicated mains supply - what fuse?

[Nuuk]

If you have a dedicated mains supply for your hi-fi, what value fuse or circuit breaker should you use in the consumer unit?

I am currently using a 10A circuit breaker.

[sbrook]

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).

[Nuuk]

Well mine was done back in 1992 when I rewired the whole house. I am mainly interested in what value of fuse/cb is optimal for a circuit powering only hi-fi.

[Juergen Knoop]

Originally posted by Nuuk
I am mainly interested in what value of fuse/cb is optimal for a circuit powering only hi-fi.

the max. value is determined by regulations, the min. value is determinend by your choice. But what is achieved with an undersized fuse/circuitbreaker?

[richie00boy]

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.

[Nuuk]

So if I have something that needs more than a 10A CB just fit a bigger value?

10A has worked well for me but I now have a large power amp that trips the breaker when I power it up.

[sbrook]

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.

[Nuuk]

I'm using the old 15 amp round-pin plugs on some of my gear which is why I was happier to use a 10A CB.

I think rather than increase the value of the CB, it is best to add a soft-start to the power amp.

[sbrook]

Circuit breakers SHOULD cope with the surge current. After all motors usually produce far higher inrush currents.

[Juergen Knoop]

in germany only fast type B circuitbreakers are allowed for home use.
Slower C or K types are restricted to industrial enviroments.
From personal experience 10A CB jump happily on surges.
Regards