What Went Wrong? Minor Electrical Explosion...

[OnlQQker]

My ex mother in law has 2 OLD candlestick (Brass) lamps.

The switch stopped working so I took it apart, it looks like this but plastic switch and cover BC SWITCHED BRASS LAMPHOLDER - https://www.bltdirect.com/bc-switched-brass-lampholder?adcid=pla&_intent=HIGH&utm_source=bing&utm_medium=cpc&utm_campaign=Shift%20-%20Shopping%20-%20GB%20-%20dencon%20-%20HIGH&utm_term=4578778785434673&utm_content=Shift%20-%20Shopping%20-%20GB%20-%20dencon%20-%20HIGH%20-%20arkansas-north-william-winter%20-%206cc6a506bd234d4d9d26efa173caa7e9

I very carefully took one apart and inside the switch was some very small brass contacts. I cleaned them all up with some very fine sandpaper as they were filthy. I actually dropped one of the parts and it was 5mm square in size. Fiddly job but all worked fine.

Then the bulb was flickering, so I changed that for the one in the loft (around 1980 bulb @ 60w )
For 24 hours this worked fine and the ex mother in law was extremely pleased with it. She said it reminded her of the olden days with the warm yellowish glow.

Anyway 24 hours later and my ex wife said she tried to remove the lamp shade to straighten it up when it literally blew up. She did admit to being forceful as she does not like the lamps. It tripped the rcd but in the meantime blew the bulb out as well as the springed prongs within.

Any ideas?

 

[Deleted account]

Either fitting not secured, conductors loose, conductors not fully terminated.

 

[pc1966]

Perhaps divine retribution?

Also did it have 3A or 13A fuse? Would make a bit of a difference to fault energy.

 

[buzzlightyear]

Anyway 24 hours later and my ex wife said she tried to remove the lamp shade to straighten it up when it literally blew up. She did admit to being forceful as she does not like the lamps. It tripped the rcd but in the meantime blew the bulb out as well as the springed prongs within.

 

[OnlQQker]

Perhaps divine retribution?

Also did it have 3A or 13A fuse? Would make a bit of a difference to fault energy.

3 amp fuse, all I did was undo the red/blue terminals from below the bulb bayonet and the earth was fixed below the bayonet so no need to remove that. I have a bad habit of doing things up in 3 stages, tight, bit tighter, and then that 3rd tightness you get used to where you know it's tight. But not butchered tight!

I'm a bit at risk of over thinking this, the bayonet cable comes in at the bottom of lamp and has green/earth red/line and black/neutral. 1mm cable which visibly looks ok.

One thing I did struggle with, there was no L/N sign on the bayonet terminals below, but then I can't make out why it worked for 24 hours until it was mishandled and blew up?

 

[Deleted account]

3 amp fuse, all I did was undo the red/blue terminals from below the bulb bayonet and the earth was fixed below the bayonet so no need to remove that. I have a bad habit of doing things up in 3 stages, tight, bit tighter, and then that 3rd tightness you get used to where you know it's tight. But not butchered tight!

I'm a bit at risk of over thinking this, the bayonet cable comes in at the bottom of lamp and has green/earth red/line and black/neutral. 1mm cable which visibly looks ok.

One thing I did struggle with, there was no L/N sign on the bayonet terminals below, but then I can't make out why it worked for 24 hours until it was mishandled and blew up?

Very very important you get the L & N the right way around on these light fittings. It will still work if it’s not, but the line conductor must be able to be switched off. Not the neutral.

edit: I noticed it’s not an Edison screw, if it was polarity would be even more important.

 

[Lucien Nunes]

Anyway 24 hours later and my ex wife said she tried to remove the lamp shade to straighten it up when it literally blew up. She did admit to being forceful as she does not like the lamps.

I'm a bit at risk of over thinking this,

You might be. Someone had a fight with the lamp holder, possibly unscrewed the wrong bit, it came apart inside and the line pin / terminal shorted to the casing. Next please.

green/earth red/line and black/neutral. 1mm cable which visibly looks ok.

I doubt it's 1.0 sq. mm. Most old table lamps from the red/black/green era would be wired with 23/.0076 with an area of 0.67sq. mm. When metric cables first came along many lamps were fitted with 0.5 sq. mm; more recent ones will have 0.75.

 

[GLENNSPARK]

Sounds like the missus did a "loop test" on it for you on your behalf...

 

[Rockingit]

Slightly off topic, but this reminds me of something from years ago that could have potentially killed me…. BIG clearspan marquee being covered with decor and stage lighting inside and we had a long run of brass BC holders down the ridge for some decorative effect now long forgotten, where each pendant would have been on a 1m trailing lead attached to a 16a trailing plug (commando). All got fixed on the ground, truss got winched up, connections made and a lot of them didn’t work. So up I went on a set of Zarges to one of the dead ones, gives it a wiggle and can’t see anything obvious, unplugs it and comes back to ground for a closer inspection. Plugged it back in again at the back of the distribution rack, still nothing. Reach around to unplug it in order to dismantle and part of my other hand makes contact with something at earth potential and I get an almighty whack before the RCD kicks in. Turned out that some monkeys that the company had hired to make all these up in their warehouse had wired them all as L to the Earth lug! Insulating rubber feet on the Zarges probably prevented me doing a 30’ high Superman.

 

[Megawatt]

My ex mother in law has 2 OLD candlestick (Brass) lamps.

The switch stopped working so I took it apart, it looks like this but plastic switch and cover BC SWITCHED BRASS LAMPHOLDER - https://www.bltdirect.com/bc-switched-brass-lampholder?adcid=pla&_intent=HIGH&utm_source=bing&utm_medium=cpc&utm_campaign=Shift%20-%20Shopping%20-%20GB%20-%20dencon%20-%20HIGH&utm_term=4578778785434673&utm_content=Shift%20-%20Shopping%20-%20GB%20-%20dencon%20-%20HIGH%20-%20arkansas-north-william-winter%20-%206cc6a506bd234d4d9d26efa173caa7e9

I very carefully took one apart and inside the switch was some very small brass contacts. I cleaned them all up with some very fine sandpaper as they were filthy. I actually dropped one of the parts and it was 5mm square in size. Fiddly job but all worked fine.

Then the bulb was flickering, so I changed that for the one in the loft (around 1980 bulb @ 60w )
For 24 hours this worked fine and the ex mother in law was extremely pleased with it. She said it reminded her of the olden days with the warm yellowish glow.

Anyway 24 hours later and my ex wife said she tried to remove the lamp shade to straighten it up when it literally blew up. She did admit to being forceful as she does not like the lamps. It tripped the rcd but in the meantime blew the bulb out as well as the springed prongs within.

Any ideas?

When you took the wires loose, your lamps are polarity sensitive. In other words you made the part you screw in the bulb live which should be the bottom of the light bulb live

 

[Lucien Nunes]

In the UK 90% of our bulbs don't screw in, they have a push and twist bayonet lock with two pins. The metal cap on the bulb is not electrically connected to anything, there are two contacts on the end so the polarity doesn't matter. We know this fitting is bayonet because the OP refers to the 'spring prongs' and you would expect it to be as it has old British red/black/green wiring colours. Where the lamp socket is metal it is grounded, so the lamp cap itself is grounded. With a plastic socket the lamp cap is not grounded but should be covered by a 'skirt' on the socket so that you can't touch it. Recently we have started seeing more E27 screw sockets on goods made for a global market but the native British bulb is bayonet aka B22.

What almost certainly happened here is that the person unscrewing the shade ring / skirt also unscrewed the ring that holds the socket together, and it came apart and the prongs shorted to the body. Some sockets have a lock screw to prevent the wrong part unscrewing if you are careless, but this would be old enough not to have one.

 

[GLENNSPARK]

Bar in Leeds this one time...
They'd bought a load of chinese fancy drops with standard E27s for me to fit...
Did a quick continuity check before putting em up...
4 out of 7....reverse polarity...

 

[brianmoooore]

Some newer E27 fittings aren't marked for polarity. They tend to have a brass fork at the bottom of the holder that only makes contact to the threaded part of the lamp when it is just short of fully screwed in.

 

[westward10]

ES lampholders for a long time have been non polarity biased if manufactured to the correct standard. As above the lamp only makes contact when fully inserted and by way of construction the outer screw is not accessible.