Date   : Wed, 19 Aug 2009 18:51:53 +0100
From   : info@... (Sprow)
Subject: Retro Reunited: Econet Cabling, Demos, etc.

In article <20090819162105.11227h369vq8ltgc@...>,
   <afra@...> wrote:
> Quoting Darren Grant <darren.grant@...>:

> > On 19/08/2009 13:59, "Ian Stocks" <bbcmicro@...> wrote:
> >
> >> Whilst we are talking about cabling. Any one know what happens about
> >> mains distribution? Here at work, our H&S guy has a fit if you
> >> daisy-chain multi-way extensions. I pressume they dont care at the show.
> >
> > It doesn't really matter as long as they are rated to carry 13A then the
> > fuse will blow before you can overload anything. You could have 100 
> > sockets chained together and it wouldn't be a problem as they all go 
> > through a single 13A fuse.

No you can't - as the earth return will exceed permitted resistance.

> Whilst in principle I agree with you that's not the whole story, each  
> thing plugged into the chain also has to be correctly fused too, so  
> that if it develops a fault which causes it to draw too much current,  
> it will blow it's fuse, ifen if it's not enough to blow the 13A one in  
> the main plug. This is why I tend to fit 1A fuses to most of my retro  
> gear as it's normally all they need.

The fuse exists to protect the flex to the appliance, the appliance itself
should have a fuse appropriate to its use (for example, if the appliance has
a 500mA PSU it should have a 500mA fuse in it, but might be wired up with 5A
cable so could reasonably have a 5A fuse in the plug).

Fitting a lower fuse rating than the flex rating is OK, particularly if the
internal fuse is hard to get at!
Sprow.