Any arguments against RCBOs?

[Richard Burns]

bad for technical reasons, or bad for their profits?

Hmm.. yes, one does wonder on the level of risk they claim.

Thanks for the comments. I suspect the original estimator just didn't think I'd go for the more expensive solution, so didn't do more that mention it in passing. We have 11 circuits in the house, so it sounds like it might have added £300 (Hager board). Knowing what I know now I would have gone for that. On the other hand in four years the only trips have been two resulting from a faulty dishwasher. So maybe the advantage is more theoretical than real.

So on the technical side I was trying to think whether leaving the N still connected on the fault circuit could ever be an issue, but I don't see anyone saying that.

Tony S

If the RCBO disconnects because of a neutral earth fault then obviously that fault has not been cleared and remains in place (albeit the power is disconnected from the fault). This is clearly not a good situation but in practice this will not be an issue with your setup. The problems will occur if you have discriminating protective devices in series. e.g. 100mA time delay RCD as main switch and 30mA RCBO for the circuit
On a fault the first protective device operates, as it should, however as it has not cleared the fault the next protective device upstream also operates and can cause unrelated circuits to power down and cause nuisance.

 

[aesmith]

Cheers. There's no upfront RCD on the feed to the outbuildings, it's a switch and fuse in the house, then SWA all the way to the board. The installing electrician said there was no need for RCD protection on armoured cable. That surprised me a bit because in our last house but one the electrician put an RCD in the house and fed the outbuildings from that (however that was a crap job in other respects). We're TNS by the way, and the outbuilding earths are via a third core on the SWA.

Regarding different make RCBOs, I suppose that's a moot point. If they'd offered an all RCBO solution for say £300 extra, I'm hardly going to suggest they use £9.99 parts off Ebay instead of they're preferred parts. I can just imagine the response.