What do you think happened here?

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Dodgy bulb!
The wire inside the cap, connecting the contact to the filament, was too close to or touching the cap, hence short to earth.
 
You can get a bigger bang by poking around inside a CU with an uninsulated screwdriver.

Of course, you must "forget" to switch it off otherwise you won't get the bang.
 
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These dodgy lamps make a mockery of double insulated metal light fittings.

I have found at least one lamp where the internal wire was touching the metal cap. Worked "safely" in a plastic lamp holder but tripped RCD when moved to a metal fitting. Quality control on some cheap lamps is not good.
 
That's why the 17th edition requires 30mA RCD's on lighting circuits nowadays. :LOL: :LOL:
 
Afaict under the 17th there is no requirement for RCDs on lighting circuits per-se though most domestic lighting circuits will need to be on RCDs for other reasons (bathrooms and/or concealed cables).
 
plugwash said:
Afaict under the 17th there is no requirement for RCDs on lighting circuits per-se though most domestic lighting circuits will need to be on RCDs for other reasons (bathrooms and/or concealed cables).
Click to expand...

A TT system?
 
It really is bad practice to replace lamps into live lampholders or to plug into live sockets that are not switched off.
 
Stoday said:
It really is bad practice to replace lamps into live lampholders or to plug into live sockets that are not switched off.
Click to expand...
But in practice it must happen all the time. I can't tell whether my bathroom light is on or off from the switch (pull cord). Same for lights with two switches.
 
MarkSmith said:
Same for lights with two switches.
Click to expand...
Lights with two switches should be wired so that the light is off when both switches are off (and therefore also off when both switches are on).

Whether they are actually wired like that is another matter.
 
MarkSmith said:
Stoday said:
It really is bad practice to replace lamps into live lampholders or to plug into live sockets that are not switched off.
Click to expand...
But in practice it must happen all the time. I can't tell whether my bathroom light is on or off from the switch (pull cord). Same for lights with two switches.
Click to expand...

Thats a good point - I fit a DP Switched FCU outside my bathroom door, high up, with a 3amp Fuse, and use it to isolate the light accordingly.
 
flameport said:
Lights with two switches should be wired so that the light is off when both switches are off (and therefore also off when both switches are on).
Click to expand...
And the intermediate(s) are off too.

That leaves only the old fashioned bathrooms with a ceiling switch as needing the lighting fuse to be pulled (or the MCB to be switched off).
 
D

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