RE: Lamps Blowing ...was : C-Bus and Wire-wound transformers - HELP

["Keith Doxey" <ukha@xxxxxxx>]

Without wishing to take sides in this discussion, there is an important
thing to be considered which is the total number of lamps and how they are
used.

I once had a similar discussion about crap lamp life at a pub where I used
to DJ. The owner complained that the lamps in the bar were rubbish because
he had to replace 2 or 3 EVERY WEEK.

I explained that the average life of the bulb he used was 1000 hours and he
claimed they didnt last that long so I proved otherwise. The bar had 7
light
fittings that each took 5 bulbs so 35 bulbs in total.

Assuming he was to start from a fresh installation of all 35 bulbs each
having a life of 1000 hours it would be reasonabley safe to assume that he
wouldnt have to replace a lamp for almost 1000 hours. In reality the bulbs
would last between say 900 and 1200 hours by which time all the bulbs would
have been replaced. Because the lamps would be replace when they blew the
next failures of the bulbs would be staggered even more.

The bar was open for 12 hours per day so lamp life would be 1000/12 =
83.333
days call it 84 because 84 days is 12 weeks. Therefore in 12 weeks approx,
all 35 lamps would be replaced. 35/12=2.9 which is the 2 or 3 bulbs per
week
being changed.

My suggestion that if he replaced all the bulbs in one go he could forget
about it for about 10 weeks or so was met with a reply that I wont repeat
here :-)

The usage of the lamps is also an important factor. Running a lamp at 95%
of
its rated power will greatly prolong its life, in fact in some commercial
buildings where access to lamps is difficult and costly, they install extra
lights to achieve the correct light levels when underrun. This gives a much
longer life and greatly reduced maintenance costs because they then replace
all lamps in one go shortly before they would start to fail in large
numbers. This means they only need to set up the scaffolding or access
hoists once ot twice per year.

With Mark's home lighting it is quite possible that many of the lamps are
run below full brightness and they also soft start. Given that most lamps
die due to the switch on surge this also prolongs the life.

In the case of the shop lighting, it is most likely run at full brightness
all the time and probably for 10 hours per day. Even if the lamp life was
2000 hours, if you have 200 lights then you will replace one every 10 hours
or One per Day giving the impression that they are not very reliable.

The more lights you have the more you will have fail but it does give the
impression that they are unreliable.

Just something else to consider :-)

Keith

www.diyha.co.uk
www.kat5.tv


> -----Original Message-----
> From: Mark McCall [mailto:lists@xxxxxxx]
> Sent: 16 August 2003 12:46
> To: ukha_d@xxxxxxx
> Subject: Re: [ukha_d] Re: C-Bus and Wire-wound transformers - HELP
>
>
> > Unfortunately they werent rumours :(
>
> Like I said...our experience of Main Halogens has been
> superb.  I have had
> lots of issues with 12V halogens in work were we go through a colossal
> amount of them.
>
> You can get good and bad in both systems I'm sure.
>
> M.
>
>
>
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