main RCD trips before RCD 30ma spur

[king_11]

sorry it is a power shower! so cable is fine

 

[Des 56]

sorry it is a power shower! so cable is fine

I am puzzled by that response, if it was meant as a reply to my post

 

[Octopus]

So all you need to do now is remove the RCD on the fused spur .....

 

[king_11]

ive got a feeling someone put that in to stop it tripping out the house, (because it kept tripping) but who knows, ill give it ago

 

[nickblake]

ive got a feeling someone put that in to stop it tripping out the house, (because it kept tripping) but who knows, ill give it ago

No it wont stop that, if it did keep tripping then the circuits will require testing to ensure that there isnt an underlying fault there some where , so take out the RCD fused spure change with a normal one fused at 3 amps and carry out some IR tests but be careful not to damage the pump ,

 

[morph]

sorry it is a power shower! so cable is fine

what a surprise........... not....... ha ha

 

[giio]

Are you saying that you have a 1.5mm cable feeding an 8.5KW shower?? or have i miss read your post??
As for the 30mA RCD spur unit, ...if the main RCD is also 30mA then your lucky they both don't trip together, as there is no discrimination between them!!!

correct ,they should both trip as the first rcd in line allows enough fault current to pass to trip the second one ,however the first should trip too,
also I've seen some sparks using a 100ma downstream of the 30 ma and they wonder why that trips too, this does not offer discrimination, a time delayed rcd is required downstream of the first one,then you need to seriously have a look that your not breaking any other regs by doing this.
a recent contract we completed was a garden centre where the incoming was then sub mained to 5 giant greenhouse, we fitted a time delayed at source and then ordinary rcds at each greenhouse, the reason was we could not allow all the greenhouses to trip if there was a problem with one,the first clears the fault before the downstream one kicks in and if it does not clear it then the time delayed one kicks in