The light bulb in one of the ceiling lights (at the top of the stairs) just
went "bang" and the glass section blew off leaving the metal part still in
the fitting. The bulb was burnt looking along one side.
Can anyone suggest what might have caused this? I took the light fitting
apart and all the connections are intact and there is no sign of any short
circuiting. The fitting is old, but I can't see any problem. I put in a
new bult and everything seems fine.
Earlier today I re-wired another light fitting (at the bottom of the stairs)
because the wiring in that one had come apart and was no longer working.
This is on a different fuse circuit from the one that blew, although they do
share a double light switch. Is it likely to be a coincidence that this one
blew so soon after?
I am not an electrician (even an amateur one) so any advice would be
I have known this happen - very rarely - I don't think it's related to the
wiring or fitings.
However, I don't like the idea of two separate fused circuits feeding the
same double switch.
Typically, someone working on the switch in the future might satisfy
themselves that, say, the downstairs light has safely gone off when they
pull the fuse - and fail to check more thoroughly before tampering with the
I see what you mean. I am not sure the wiring can be trusted here, which is
why I put the main switch off in the house (in fact two switches - don't
know why either!) before going near the fitting. I hope that everyone else
is as paranoid in the future! I don't suppose I can do anything about this.
I have never seen in any house that I have been in where they have a fused
lighting circuit for upstairs and a fused lighting circuit for downstairs, a
separate switch just for the stairs lights. Infact, allot have downstairs
hall light and upstairs hall lights on same switch.
Sorry if I wasn't making it clear. Yes - separate fused circuits for
upstairs and down are common IME. But where a double switch is operating
upstairs on one gang and downstairs on the other (common enough when stairs
/ halls etc can be controlled from up- and down- 2-way switching) then AIUI
both gangs (and hence both up and down lights) should be supplied from the
same fused circuit.
Yes -- it's the same issue which sometimes results in MCB's
and fuses blowing when a bulb blows. The filament breaks and
causes a small spark. The spark keeps the current flowing.
The spark is lower resistance than the filament (gross over-
simplification), so it grows in length, walking along the
filament back to the lead-in wires. At this point, it is
shorting out the supply. This all happens extremely quickly,
and you will see the bright flash from the spark (arc).
Normally this blows the built-in fuse in the lead-in wires.
Sometimes it also trips an MCB or fuse for the circuit. If
the fuses/MCB don't operate fast enough, the heat generated
by the arc will cause the gas to expand in the bulb and blow
the glass off. This is quite rare; I've only personally
experienced it once in the UK. It's more common in countries
where filament lamps don't routinely include fuses.
Ignore the incident. It might have been a faulty bulb, in not
having fused lead-in wires.
I have seen this. It was quite remarkable. The lamps were new but the
building was old and damp. I do believe condensation may have caused the
glass to shatter in this case. The best bit was that the light stayed on for
a good 30 seconds before the filament died. There was a bang, the room went
dim then bright then slowly faded into darkness
Pure coincidence. I cannot see how you could make a lamp explode on a single
phase circuit no matter how it is wired up.
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