Electrical question

What's an RCD?

All those quals and can't search, doh! Jaymack

You said earlier:-

From: Craig Cockburn Subject: Re: Electrical question Date: Fri, 04 Aug 2006 07:55 Newsgroups: uk.d-i-y

To reset it, I just push it down again, it's not sealed.

I'm surprised you've not had this before. Whole house RCDs have a habit of tripping when a bulb blows etc

You pull a sad face at the arrangement, yet the unit appears to be a Wylex standard consumer unit. Has an RCD been wrongly fitted in place of a plain ON/OFF switch? The RCD looks a factory fitted arrangement from the photo.

( this is not any help answering Craig's original question as to why the RCD tripped.)

Roger

Made me wonder....

Dave

You have seen many then.

Yes

No, that's MCBs.

In message , "Dave Plowman (News)" writes

In the past when a bulb has blown, it's just the local circuit which goes. I might have known more about the other switch behind the fuse if the unit had been situated in a place where I could see said switch without having to do contortions to have a look at it.

just switch the damn thing back on and forget about trying to become an electrical engineer.

Those trip switches are a safety mechanism and can sometimes be triggered by the most unlikely things.

Try understanding the yorkshire ripper case if you want a real puzzle.

More coffee needed.

Well perhaps, but the electrician managed to wire it up the said switch so it must be possible.

Jim A

RCDs obviously shouldn't trip when a bulb blows, provided that it's a simple near-short-circuit, not involving earth. But in practice they are not completely immune to very large common-mode current surges. I've had one trip at the old house.

My split load CU has the lighting on the RCD protected side - despite advice on here, as I consider fiddling about changing bulbs on a possibly live circuit - say two way switched - to be as hazardous as other things. But if it proved a real problem they could easily be swopped to the non RCD side as there are spare ways.

And the one time it has tripped was when a bulb blew which also took the appropriate MCB.

In message , John McLean writes

When I go to toastmasters, they penalise people for using jargon. You should try it sometime.

We're discussing a technical subject and you need to know the terms to deal with it, its not the same as giving talks to people that dont need to know the technicalities. Try discussing computers, diy and so on without jargon and you wont get very far.

NT

It tripped because either:

- a load has earth leakage, which may be safe or unsafe

- combined loads exceed the rcd's leakage tolerance

- a mains spike that caused transient load current imbalance

AND the poor design of having a large number of loads on one RCD

NT

FWIW deaths per year by electrocution from lighting circuits is

All hall/stair lights are on a non RCD circuit.

While I agree with the above you havn't addressed my point.

The Wylex 'consumer unit' is shown fitted with a whole house RCD and appears to be as manufactured. Has the installer wrongly fitted a unit intended for another purpose?

Roger