Even tripping the circuit breaker may not give you full protection. You need to either trip the RCD or the Main Incoming CB as they are dual pole and a standard CB is single pole.

One (irrelevant) point on 999.
Used to be a problem from an internal switchboard when you dialled 9 to get external line, and 99 for local call (eg Peterlee->Durham).
If you were on an outside line when you thought your weren't, accidental 999 call.

In reply to a post by cheshire_man:

I don't think I'd change a ceiling rose without switching off the circuit - and checking all the wires in the rose were dead.

Obviously your advice is extremely good - particularly the checking (even after switching of the circuit) that all wires are dead!

Some years ago I failed to do that & got a very nasty jolt from a still-live connection - which wasn't a good thing as I was on some step-ladders on the landing at the top of the stairs!

I was trying to replace the ceiling rose of the landing light &, as you do, put the light on & then pulled the fuse ensuring that the light was now disconnected/isolated.

To cut a long story short, I discovered that this upstairs Light (because of 2-way switching) had been fed from the downstairs light cct & not from the upstairs light cct. However, for convenience, it had been installed using the upstairs' Neutral & the Rose had BOTH the upstairs Neutral & Line connected (although the Line connection was not feeding the switch - just being used as a connection point).

Hence, although I had isolated the "active" Line (from the downstairs' cct) the "non-active" Line (from the upstairs cct) was still live!

I think, at the time, I said something like "Oh dear how unfortunate"!!

I always phone up the Electricity company and have them disconnect my town from the National Grid before letting the wife change a light-bulb.

Sorry, when I said CB I probably meant RCCB, it's the one in the main Circuit box that trips automatically when there is a fault in the circuit, I have an older system, that has 2 push buttons (rather than a switch) on the front, a small one to trip and a large one to reset , the Main incoming CB is inacessible as it is controlled from a locked cupboard in this Council Block, even the Power companies cannot gain access without getting in touch with the council, found this out when they wanted to change my meter to a new type recently, and the EDF engineer didn't have a key.

Apart from the technical aspects, I recollect from visiting Aberdeen Telephone Exchange in 1950, just after the Emergency Call procedure was introduced there, that 999 was-

a) relatively easy for the Blind and Partially-sighted (and others in the dark) to locate

b) was less likely to be dialled accidentally by younger children, reaching up and playing with the rotary dial.

In the Exchange, such a call was identified by a flashing red light, if I remember correctly.

Before that, there were the Emergency Phones in Police Boxes (of the classical design variety in Edinburgh etc; and "Doctor Who" variety south of the Border.

Edited by deleted (Fri 10-Jan-14 12:42:06)

As well as an RCCB in your CU there should normally be a main incoming CB too.

Just a big ON/OFF switch for if you need to get to the wiring behind it.

That is the one ... so just a Switch Disconnect and not high current breaker.

I suppose so, I know it turns everything off, I'm no electrician and wouldn't dream of touching anything except the CBs (RCCBs), before doing any work, like changing roses, light switches or sockets and that's my limit.

Edited by The_Voyager (Fri 10-Jan-14 19:01:33)