RCD Light Switch Tripping?

just another related question, i need to provide rcd protection for my lighting circuit as i'm adding downlighters in the bathroom. i only have one cb spare space on the wylex cu and the only rhd current is covering sockets cooker etc. can i install another rcb in place of the isolator switch or can i get an rcb the same size as a cb. cheers andy

andy b
May 2009

Thank-you for the quick response. Sorry my terminology. It is an RCD, and the light circuit is the one tripping. Will try as you suggest, would this still trip with all light switches off? Afraid Alarm is on light circuit, was like that when we moved in. I guess they figured the main ring is more likely to trip than lights. We normally get a trip when a bulb goes, but then it comes back on when we reset.

Got a spark coming out in anycase, but I will check the bulbs before he comes :) - might be able to cancel if that works!

Thanks Again

Carl
November 2008

Most consumer units have just one RCD that supplies all the other circuits and also acts as an isolator switch. From what I can glean from your problem description the RCD is not constantly tripping (else you could not have power to the sockets) and just the lighting breaker is playing up.

Take out all your light bulbs (not those powered by sockets of course) and see if the lighting breaker is still tripping - you may have broken fillaments across the lamp base inside a bulb causing over current. This would trip the lighting breaker but not the main RCD because current in Line and Neutral would be equal.

If security alarm is on lighting breaker circuit (surely not?) disconnect it before trying the bulbs.

Peccavi
November 2008