In article , Roland Perry
writes
In message , at
12:04:27 on Sat, 13 Feb 2021, John Rumm
remarked:
On 13/02/2021 11:40, Theo wrote:
Roland Perry wrote:
I've got GU10 LED downlighters in my extension, supplied by the
builder's subcontractor (so a bit arm's length).

So far, about 8 months later, four of the twelve have failed. They start
flickering for a few days, then go very dim. On about 12hrs a day.

Contacted the supplier (Meridian) who wouldn't comment on how long they
were supposed to last [see below], but sent me two replacements.

The box says "2yrs Guarantee", which is 34hrs a day at the "average
life" of 25k hrs.
If the MTBF is 25k hours that means some proportion of them are
going to
fail before 25k hours. If that was a median TBF it would be half of them.
But they've run about 3k hours, so it's hard to think of a distribution
where a third of them would have failed at that point.
I suppose this is the hazard of fitting lights with unreplaceable
lamps - it
only takes one of them to die to make the rest of the installation look
bad.

GU10 suggests replaceable lamps rather than permanent ones.

That's right - theyare easily replaced.

The usual problem with LED lamps is their ability to shed heat, and
that is heavily dictated by the enclosure. Many GU10 fittings will
leave the lamp completely exposed - and one would expect that to give
adequate cooling. Fully enclosed in a downlighter - especially if
covered in insulation could result in much higher run temperatures and
so dramatically shorter life expectancy.

Being in the ceiling of an extension they are very well insulated to
the side and above.
I had the same issue with our extension. So up in the loft I carefully
created a space in the insulation around each fitting. Then when
boarding over I cut a circular hole over each bulb to allow the heat to
rise. Covered the hole with mesh to prevent the inevitable.
--
bert