UK Help me understand this RCBO?

[roxalford]

Hi and thank you for having me in your forum.

My background is more electronics than electrical but I'm reasonably competent with UK mains, however this has me baffled.

I'm confused by a RCBO which I got the other day to feed an appliance that draws like 40A peak.

It has a Live input at the bottom, which goes to the L bus.

At the top there are L out and N out screw terminals, and also a blue, hard-wired, flying lead, with a crimp terminal end, which I gather goes to the N bus bar.

So if the circuit goes directly into L and N out, doesn't that mean that ALL the return current on the neutral side is going to go via that tiny flying lead?

That can't be right, surely? It's a 40A C rated RCBO, and it just doesn't feel Iike that thin wire is safe for 40A.

So I must be missing something, as there doesn't seem to be any other neutral line closing the circuit. And no instructions supplied with the device.

Can anyone explain what's going on?

Cheers!

 

[littlespark]

It's right...and other manufacturers have it the same way.

Although the outgoing cable could be 4mm/6mm/10mm whatever, the neutral tail to the bar is only that thin blue wire... 4mm at best.

The devices will be tested by the manufacturers and specced to BS61009... It must deem this size of cable adaquate for the task

 

[roxalford]

Good grief!

Every day's a school day

In that case though I think I'll shorten it, is there any reason why I shouldn't halve and re-crimp it?

Not strictly necessary I guess but it's way too long to be neat.

Thanks for your help

 

[littlespark]

yes... you can cut it, but definately crimp the end up again with a suitable ferrule crimp

 

[roxalford]

Cheers, appreciated