Dead blue bulb

If it's a brass holder. Most are plastic.

And the bayonet cap is OUTSIDE the glass, the filament is INSIDE the glass. 240 volts don't go through glass. Any electricity inside the bulb can only go one way, into the neutral.

Standard white coated, Philips 60W.

Reply to
Tough Guy no. 1265
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Yebbut the glass envelope is sealed, and there are only two wires through the glass, live and neutral. How can there be a connection to earth, even momentarily when the filament vaporises, if there are no earthed wires within the envelope? Are you saying that there's capacitative leakage through the glass to the bayonet cap?

Reply to
Chris Hogg

Who knows with those stupid ELCBs. I remember when I was at primary school they put one on the computer, at that time a BBC Micro with a cub monitor, metal chassis. If someone touched the screen and the chassis at once, they obviously got a static shock, this was enough to trip the stupid device.

Reply to
Tough Guy no. 1265

ol they put one on the computer, at that time a BBC Micro with a cub monito r, metal chassis. If someone touched the screen and the chassis at once, t hey obviously got a static shock, this was enough to trip the stupid device .

that's RCD behaviour. An ELCB wouldn't care if you fried, as long as it did n't raise the whole house earth ('frame' to be precise) voltage to 50v.

NT

Reply to
tabbypurr

I'd never heard of those. I thought they all compared live current to neutral current, and ELCB was just another name for RCD. Sensing the voltage on earth doesn't seem like any protection at all, and I don't see the point of it. Firstly the naughty current has to go through the earth wire, and not another earth, and secondly there has to be enough impedance before it to cause the voltage to go up.

Reply to
Tough Guy no. 1265

Presumably vapourised filament (tungsten as gas) condenses on the relatively much colder (than vapourised filament) glass surface.

I've seen the effect before, rarely, and there's never much filament left inside the bulb, whereas when most bulbs blow you can see a fair bit of filament still attached to the feed electrodes. So yes, I can accept that it depends on the failure mode of the element, specifically whether it fails in a way to support a prolonged enough arc to vapourise a significant amount of element.

Reply to
Denis McMahon

chool they put one on the computer, at that time a BBC Micro with a cub mon itor, metal chassis. If someone touched the screen and the chassis at once , they obviously got a static shock, this was enough to trip the stupid dev ice.

didn't raise the whole house earth ('frame' to be precise) voltage to 50v.

utral current, and ELCB was just another name for RCD. Sensing the voltage on earth doesn't seem like any protection at all, and I don't see the poin t of it. Firstly the naughty current has to go through the earth wire, and not another earth, and secondly there has to be enough impedance before it to cause the voltage to go up.

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explains how they work & what protection they give. But unlike RCDs that ha ve replaced them they offer no contact shock protection. They were however an important move forward in safety when mandated in the 1950s.

NT

Reply to
tabbypurr

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