Electrical problem

[Steve Peake]

One that has us stumped:

In bathroom had a light fitting that one day suddenly stopped working. First thing tried was to change the light bulb (screw type) - no luck. Got a normal pendant and fitted this to the wiring and it worked. But when I got a replacement bathroom fitting and wired up the light it doesn't work again.

So at present still using the normal pendent light. Have tried three different fitting still no luck.

Appears to be :

Junction Box-----two wire Join------fitting.

Have tried to replace the wiring between the join and the fitting with no luck, the wiring appear to be live at the fitting anyway.

Any ideas on this one?

(Not me, posted in the third party)

Steve

[BigWallop]

It sounds like a loose neutral connection, or the bulb being used has been busted during all the taking down and putting up again.

A neutral break will show as a live supply when you use a mains tester screw driver, and to make sure that the circuit is actually continuous through all conductors you need to use a multi-meter to test it. It's called a continuity test.

[Steve Peake]

I know the bulb is fine, it was swithced between a screw for the old fitting and a baynet for the temp one.

Could you explain this one, would that mean that the Neutral side is live?

Steve

[dennis]

I have had screw in bulbs that fail to make contact with the centre connector. I had to apply some solder to make them work.

[BigWallop]

No, the neutral side is completely dead because it's broken or disconnected somewhere. For electricity to be useful it must flow correctly back to the supply from whence it came, this needs the use of two insulated conducting paths (Live and Neutral). If the live is still properly connected and unbroken then a test with a mains tester screw driver type of device will show it as live, but the same tester won't show if the neutral path is still fully operable.

The use of a meter to check that both live and neutral paths are still properly connected is the only safe way to make sure that the circuit has a continuous loop for the electricity to flow around. So, the fault you have sounds by your description like a break or disconnection on the neutral path away from the circuit, as you say the live is still show OK on your mains tester screw driver. Is this correct? But you have no means to safely test the neutral path for breaks or disconnection so you can't say it is OK by using your tester screw driver.

It could also be the switch that has gone belly up of course.

[Mike Dodd]

2nd'ed with the screw caps.

Also, had the same with bayonets - although these tend to work if "wiggled".

[Steve Peake]

Thats something to check, not sure how the basic pendant fitting seems to work fine, but the bathroom fitting doesn't though.

The other post about the batch of bulbs being too short for that type of screw fitting also sounds possible (as the pendant has baynet so it wasn't the same type of bulb fitted)

Cheers All

Steve

[Peter Andrews]

You don't describe the fitting but... I was called out by a friend who had changed the lamp in the shaving light but it didn't work. However I refitted the lamp cover - which has a contact on it - and then it was OK.

Peter

[Mogweed]

A mate of mine has completely rewired our house so everything in the installation is brand new, including the split-load consumer unit. We have an upstairs ring main, downstairs ring main and a kitchen ring main, all of which are protected by the RCD, and the problem is the kitchen ring.

As soon as *anything* (portable radio, halogen lamp, electric drill or whatever) is plugged into *any* socket on the kitchen ring, the RCD trips (plugging the same things into either upstairs or downstairs rings does

*not* trip it).

Splitting the ring at the CU and using a proper Megger (500v insulation resistance tester, not just a multimeter) to test each leg of the ring shows the following:

L-N = almost infinity resistance (certainly over 1,000Mohms anyway) L-E = " " " " " " " N-E = " " " " " " "

so no short-circuits, but yet the RCD trips. What's the problem - more importantly, what's the solution to the problem? :o)

TIA,

Mogweed

[The3rd Earl Of Derby]

Are you 100% sure you don't have a short?

Have you been capping back the cable into chases, Screwed down floor boards?

-- Sir Benjamin Middlethwaite

[Lee]

Have you checked for a misplaced neutral? 'Tis a common mistake on a split load CU...

Lee

[Mogweed]

You have to believe your instruments so I can only go on what the megger tells me, and that says that there is no short - tried shorting the test leads and the meter swings right over to 0 ohms so the megger seems to be working OK. Cables capped - and chases plastered over :o( Some floorboards screwed back down - but megger shows no shorts.

Mogweed.

[The3rd Earl Of Derby]

Take the kitchen strap out of the CU attach a battery&bulb L to +, - to bulb and bulb to N and see if the bulb lights? do this on the E to L and E to N. If it lights you have a short if not then start looking at CU

-- Sir Benjamin Middlethwaite

[Mogweed]

Cheers Sir Benjamin, I'll give it a go.

Mogweed.

[Frank Erskine]

That does sound like the problem - possibly a neutral swapped with an earth, otherwise the RCD wouldn't trip with a non-earthed item such as a radio.

[Mogweed]

Ah, now then, I haven't checked for that - mainly because I didn't know that a neutral could be misplaced. They all go to a common bar don't they?

Mogweed.

[Gary Cavie]

As a portable radio, which presumably is double insulated, is also tripping it, it suggests that the fault is not on the earth, so I would guess that there is either a neutral leg or a live leg connected to the wrong side of the RCD.

Alternatively, if it is a Wylex S/L board, there have been quite a few faulty RCDs coming from them of late - at least in our neck of the woods. Doesn't explain why it is only one ring which causes the problem though. I'd check first that the ring is terminated (both conductors, both legs) on the correct side of the RCD first.

[--s-p-o-n-i-x--]

Faulty RCD? If they are the same value try swapping two and see if the fault moves.

sponix

[Steven Briggs]

In message , Frank Erskine writes

Yes it would, if the kitchen ring neutral has been returned to the non-RCD busbar. A common and easy to make mistake.

[Mogweed]

Thanks Gary, I'll check that - and it is actually a Wylex CU but as you say, if it was a faulty RCD it should show up on the other rings too.

Mogweed.