Numerous RCD's, selectivity

[gazdkw82]

Looking for a little advice.

I was speaking with a colleague who was confused about a circuit design that doesn't offer much selectivity.

A sub main is being fed via a SWA to a 63A commando style outlet which is to be used for temporary set ups (shows, Marquess etc).

The circuit is protected at circuit origin via a 30ma RCBO. All events that are plugged in use our little temporary boards which are movable. These temp boards have a little C/U with 4 circuits each. All circuits are again 30ma RCBO's.

My colleague was concerned that in the event of a earth fault on a circuit, there is no selectivity on which RCBO would trip. It would be a nuisance if the RCBO supplying the 63A outlet was to trip. I suggested possibly a time delayed RCBO at the circuit origin, however under the 18th all outlets up to 63A require 30ma rcd protection and I'm pretty sure you can't get a time delayed 30ma RCBO.

Any advice?

 

[Strima]

The only logical solution is to complete a risk assessment to omit RCD protection for the circuit.

 

[gazdkw82]

The only logical solution is to complete a risk assessment to omit RCD protection for the circuit.

True. And in all fairness, there is nothing to say an SWA needs Rcd protection.

 

[Charlie_]

RCD Protection upto 32 amp, not 63 amp

 

[Nigel]

True. And in all fairness, there is nothing to say an SWA needs Rcd protection.

As Strima says document a RA. Insisting all circuits plugged into the commando socket must be RCD protected and possible having it labelled as such would be sensible mitigating examples.

 

[Strima]

RCD Protection upto 32 amp, not 63 amp

Good spot, that'll teach me to read the post properly...