Lighting fuse keeps blowing.

I hope this question isn't too mundane for the group:

I have an Ikea Beryll light fitting
http://www.ikea.com/gb/en/catalog/products/70043483
fitted with four 20W halogen bulbs.
I'm based in the UK so I have a 240v mains supply.

With 4 bulbs drawing 20W @ 240v I've got a total draw
of 80W @ 240v.
I make that 0.333 amps. (W/V = A, or 80/240 = 0.333).

So why do the 8 amp, 250V, quick blow fuses I'm fitting
into this light fitting keep blowing after a few hours
operation?

 

The link takes me to a description stating 12v, not 240v, lamps.

Which is important, because it means that the mains supply is connected
to a transformer, not directly to the lamps.

The rest of this is written on the basis that there is a transformer in
the base of the lamp fitting.

That it runs for several hours before blowing the fuse puts the
suspicion on the transformer. Something with a bit of thermal mass is
needed to produce that sort of delay.

What I suggest that you do is take the fitting down and inspect what
wiring you can get to, to see if there are any bare wires that could
move and touch something.

There are other tests that can be done to prove that the transformer is
faulty , but they either need test equipment that you probably don't
have, or need test methods that should be done under the supervision of
someone qualified and experienced.

Unless you have such tools and/or the expertise, all you can do is
replace the transformer, or the complete light fitting.

It would probably be possible, and cheaper, to replace the transformer
with an external one, extending the 12 volt wiring from the lamp fitting
to reach the nearby transformer. However, this will prbably mean that
the 240v wiring would need to be extended too - so best left to someone
experienced in such things.