Curious - RCD

[ey143]

Hi

I'm curious to know, but if you have an RCD on the main fuse board and an external socket with an RCD built in, assuming both RCD have the same level trip fuse, am I right in think that the external socket RCD will always trip first and that the main fuse board RCD will not trip?

Perhaps I'm not asking the question accurately but I think you get the gist of what I mean.

 

[winston1]

No you are not right. Either might trip first or both will trip.

Thee is no point whatsoever in having two RCDs like this on the same circuit.

 

[JohnW2]

Thee is no point whatsoever in having two RCDs like this on the same circuit.

Indeed - provided that, if one only has one, it is working satisfactorily. It has been said that an appreciable portion of RCDs in service are faulty.

Some people (particularly the 'risk averse' amongst us) feel that, particularly in high risk situations (e.g. outdoor equipment/appliances), there is something to be said for the 'belt and braces' approach of having two. After all, people have come to expect dual braking systems in their cars etc.

Kind Regards, John

 

[bernardgreen]

If the fault is in the cable between the two RCDs then it is possible that only one ( upstream of the fault ) will trip.