half our lights have stopped working - any ideas ?

[news]

Hi guys - any ideas gratefully received

Up to a year ago we had old consumer unit with big fuses that we had to wind wire round. If a light bulb went then, the rest all worked still.

A year ago we had some building work done and got electrician to replace consumer unit with modern one. Since then if a light bulb goes, none at all work, switch trips on consumer unit and we have to reset it.

Electrician reckoned wiring c25 years old, no earth in lighting circuit, all lights definitely on one circuit. (OK we'd like to get it re-wired, but don't have the money at present).

This morning bulb went in son's bedroom. All lights went out, switch tripped on consumer unit as normal. Replaced bulb, reset consumer Unit switch, lights came back on.

Then, a minute or so later for no apparent reason, all lights went out for about 2 seconds, consumer unit didn't trip, half lights came back on (most downstairs) and most lights upstairs remained off. Good thing I have lots of lamps ;)

Never had this before, weird ...

Husband is not clueless :) he can check for obvious things, but is no good with multimeter ... Any ideas gratefully received for obvious things he can check over weekend before I resort to calling out electrician.

Val

[Bill]

In message , news writes

Hi Val, good luck.

What sort of fitting was the blown bulb in? Was it a round one with the flex hanging down from the centre? These tend to have the mains feed passing through them to the next light. Therefore my first thought is that when the bulb was changed you may have pulled on the flex and disturbed a loose connection in the fitting that then moved a bit disconnecting the loop through to the other lights. Just a thought and probably wrong but maybe a good place to start. I'm sure others will come up with ideas too. A look at

may give an idea as to how the wiring goes.

Just make sure your husband turns the power of at the consumer unit and not just the light switch.

[Roger]

The message from news contains these words:

Typical with MCBs and incandescent bulbs. A problem I solved by switching to compact florescents but be aware that the majority of regulars on this ng absolutely detest such bulbs. A alternative is said to be swapping the Type B lighting circuit MCB for a type C.

I would have said a good bit older. My late parents bungalow was built in 1968 and the lighting circuits in that had earth wires.

That sounds external. Power surge followed by the powerline switchgear temporarily disconnecting perhaps.

House lights are almost always daisy chained together as a radial rather than being on a ring like power sockets but with a single MCB for all the lights that might involve two radials straight from the consumer unit. Either way if half the lights are out and the MCB didn't trip there is a failure in the wiring somewhere along the line. Could be as simple as the upstairs radial connection at the consumer unit has fallen out but given the associated temporary power failure I think it is more likely to be a loose connection somewhere in the wiring, or possibly vermin damage.

Opening up the consumer unit brings you into close proximity to lethal voltage so only do that if he is certain he knows what he is doing. If the fault is anywhere else it almost has to be on the radial either at the last lit ceiling rose (assuming a loop-in system) or at the first unlit rose if it is a loose connection, or anywhere in between if it has been vermin damage that finally failed.

[news]

In message , Bill writes

Yes

Thanks. We were going to check all the wires were still connected in the switches, will do so also in the light fittings.

Will do :)

[news]

In message , Roger writes

Good :) that makes sense. All houses here are Georgian or older, overhead cables for electricity and BT lines. The area often gets power cuts.

He won't go near that !

Thanks - he will check those

:( We do have cob walls and sometimes I lie in bed hearing things walking around in the loft above me ...

[tinnews]

It's no more lethal there than in the light fittings or anywhere else. The only place(s) it might be said to be a bit safer would be on circuits protected by an RCD.

In addition consumer units often have warnings in large letters plastered all over the inside so one tends to take more care than when poking around light fittings and such although the dangers are near enough the same.

[<me9]

There's much more energy available to vapourise conductors and spray the sparks into eyes and burn.

Like dropping a spanner on a car battery terminals, but 20 times as big.

[John Rumm]

With the way most lighting circuits are wired, a loose connection in a switch would only prevent that one light from working - not all of them.

[John Rumm]

You may get some more clues to the age from this thread:

that if it turns out you have rubber insulated wires, you will have to take very great care moving or touching any wires since the insulation will likely just crumble and fall off!

[tinnews]

It's *very* difficult to do anything like that in a CU, close to impossible. OK, if you start undoing lots of wires and waving them about you *might* get something exciting, but in the context of this thread it's the voltage being able to hurt you that's relevant.

[Roger]

The message from [e-mail] contains these words:

Only to those who wouldn't think to isolate first. Very few premises have an isolator between the company fuse and the consumer unit which could render the permanently live bits in the consumer unit safe during any investigation.

[Bill]

In message , Roger writes

I have such an isolator and I thank the guy who fitted every time I do any work on the consumer unit.

>

[Andy Wade]

One common situation where that doesn't hold though is the conduit-wired installation, particularly pre-WW2 house wiring with 2-plate (i.e.

2-terminal) ceiling roses. The loop-in wiring system of that era had the neutrals looped from rose to rose, while the line was looped via the switches. (So the conduit drop to a 1-way switch had three wires: line feed, unswitched line to next switch, and switched line to rose.)

[news]

In message , Bill writes

I love this newsgroup :) I'm a long time lurker who rarely contributes as I don't think I'm as knowledgeable as most of you guys, but I've read it for years and years while we've been doing up this old house and it's helped us no end.

Spot on ! thanks :) it was the 4th light he checked this morning, one wire was clearly loose and it was a light fitting that hadn't had a bulb blow or anything ....

I did look, but I'm not much wiser ... There are 2 wires, both plastic coated, one is black and other red. Part of the lighting circuit dates from 1988 (we know that for sure as it was an add on built then) and that has the same wiring as the rest of the lighting circuit, just 2 plastic coated black and red wires.

Thanks everyone. You saved me an electrician's bill :)

Val

[Bill]

In message , news writes

Not bad is it!

Glad you got it sorted.

[Roger]

The message from news contains these words:

If there were just two wires (rather than 2 pairs of wires) I can't see offhand how the disconnection took out half the lights. Surely it should have only taken out that fitting if there was nothing daisy chained beyond it?

[Malcolm Race]

Tried it - doesn't seem to make much difference.

Malcolm

[John Rumm]

It can help, but it won't stop mains halogens from tripping them. With ordinary bulbs a type C will cope without tripping, but it also depends on your house power supply to an extent. If you have a particularly low supply impedance then you may still get regular trips.

[news]

In message , Roger writes

In that case he probably meant there were 2 pairs of wires as it took out 8 lights. Can't ask him now to check, he's gone surfing ...

Val

[Harry Bloomfield]

news explained :

That is normal behaviour for MCB's. MCB's provide a much closer protection and respond much faster than wire type fuses to surges and etc.. As a lamp blows it can draw a short but large burst of current, thus tripping the MCB.

On a 32amp ring main 13amp plug circuit, you will usually find that the

32amp MCB trips leaving the fuse in the plug top of the faulty appliance intact. It is simply due to the much faster response of the modern MCB, when compared to the speed of a wire type fuse.