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Topic Title: Lamps failing prematurely
Topic Summary: Yep, that old chestnut
Created On: 30 July 2013 08:42 PM
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 30 July 2013 08:42 PM
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Grumpy

Posts: 452
Joined: 09 January 2009

I've had this so often, "surges", "spikes" etc that for the last two years, much to my wife's astonishment, I have kept a log of the failure of the 20 GU10's in my kitchen/utility. It will be no surprise to learn that lamp failure appears to be entirely random.
So I had a call today from a landlord, the tenant says that the cfl's in the outside light fail "almost immediately" will I call round. He was unimpressed by my two year research project (almost but not quite as unimpressed as my wife and children) and by my assertion that it was almost certainly cheapo lamps. My only hope was that this lamp was controlled by a PIR, a hope that was cruelly dashed upon arrival.
So, here we are, the electrician (aka the magician) has arrived, the landlord is standing there arms crossed waiting for some magic, what am I supposed to do? I reiterated my mantra about two years research, about dodgy lamps "just test it" he said! So I did, 242v, 49.9 Hz, no obviously loose connections. He seemed happy so we put in a new cfl and I fled saying let me know what happens! Is there anything else I should have done?
 30 July 2013 08:57 PM
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leckie

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Well I agree with you that it is usually rubbish lamps. Regards testing, what did you test? I would test R1 + Rn. Just to check for a dodgy neutral connection. This test is not required on a lighting circuit in order to comply with BS7671 but is useful. The results can be assessed based on estimated circuit length. May be helpful. But could be caused by lots of different factors. Including misinformation from the occupant.
 30 July 2013 09:17 PM
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leckie

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As you alluded to with the pir reference, switching frequency is a big factor.
 30 July 2013 11:05 PM
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impvan

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Next time you're round to change one of the cfl's, make sure you autograph it and take a pic. Wouldn't be the first time a tenant's blown bulbs get swapped for the ones in the stairwells....
 31 July 2013 09:44 AM
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MHK

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When talking about quoted lifetime / operational hours of a lamp it is important to remember that the figure manufacturers state as the average operational hours is the point at which 50% of the lamps tested will have already failed. In reality if a lamp is going to fail it is likely to fail within the first few hundred hours of operation otherwise the lamp will more likely exceed the stated average lamp life.

For the lamps in question the average stated life for a G10 is only some 2000 operating hours and for typical CF lamps in the region of 8000 - 12000 operating hours.

Frequent switching of the lamps will have a detrimental effect upon their operating life as will temperature. Is the external light in question facing due south?

MHK
 31 July 2013 07:43 PM
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Grumpy

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Originally posted by: MHK

When talking about quoted lifetime / operational hours of a lamp it is important to remember that the figure manufacturers state as the average operational hours is the point at which 50% of the lamps tested will have already failed. In reality if a lamp is going to fail it is likely to fail within the first few hundred hours of operation otherwise the lamp will more likely exceed the stated average lamp life.



For the lamps in question the average stated life for a G10 is only some 2000 operating hours and for typical CF lamps in the region of 8000 - 12000 operating hours.



Frequent switching of the lamps will have a detrimental effect upon their operating life as will temperature. Is the external light in question facing due south?



MHK
 31 July 2013 07:45 PM
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Grumpy

Posts: 452
Joined: 09 January 2009

Originally posted by: MHK

When talking about quoted lifetime / operational hours of a lamp it is important to remember that the figure manufacturers state as the average operational hours is the point at which 50% of the lamps tested will have already failed. In reality if a lamp is going to fail it is likely to fail within the first few hundred hours of operation otherwise the lamp will more likely exceed the stated average lamp life.



For the lamps in question the average stated life for a G10 is only some 2000 operating hours and for typical CF lamps in the region of 8000 - 12000 operating hours.



Frequent switching of the lamps will have a detrimental effect upon their operating life as will temperature. Is the external light in question facing due south?



As a matter of fact it is though shaded to some extent as it's in a porch.
I hadn't twigged that the quoted operational life is an average when 50% will have failed. Very interesting makes the whole thing a lottery.
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