Failing Lamps

To the power quality investigator,
this is unwelcome news.
So do not say "my lights keep blowing",
for it will be he who will now fuse!

I wrote this little verse after much battling to get this through peoples heads - The high rate of lamps failing is SELDOM a power quality issue. Note that I am not saying never, but it is usually found to not be a power quality problem. But.....


A relatively new shopping centre that had been open about 8 months called in the local town electrical engineer as they were suddenly having to replace a number of lamps on a daily basis. They were convinced the quality of electrical supply was to blame and followed the route they did.

There were a lot of red faces, especially the shopping centre electrician, when it was pointed out that the centre had been operational for 10 hours a day (from 8am to 6pm) for over 200 days meaning the lamps had worked for over 2000 hours. Does not sound like a lot, but then the specification of the lamps was asked for and they were rated at 1000 hours. The real reason they lasted nearly twice their life is they only suffered switch-on surges once a day.

So the main cause of lamp failure is simply lamp life. Many will not believe this, but this is easily proved with a simple action; Write the date of installation/replacement (in indelible pen or good pencil) on the base of the lamp. If the lamp is lasting longer than expected, then it is simply a case of "time's up!"

In many instances it proves financially prudent to embark on a simple maintenance regime of replacing a group of lamps as soon as one fails. A classic example of this is floodlight masts. The lifting gear required to get to the lamps, and the labour involved with this, usually far outweighs the actual cost of the three or four lamps on the top of the mast!


The aim of the above section was to highlight that there are natural reasons lamps fail and that these should be investigated first! Only, and only when these have been exhausted should attention be turned to the power.

Agreed, if the power is suddenly poor (indicated by a severe, recognized anomaly), or the failed lamp is removed and is proven to be lasting far shorter than half their expected life, then is it worth investigating the power.

There is no simple answer as to why a lamp's life is cut short, and there is another factor involved - which type! There are effectively three main types of lamps.

  • Incandescent,
  • gas discharge (neon, fluorescent, sodium, etc), and
  • energy saving (which is effectively a miniature gas discharge).
  • We investigate all three.


    Before you delve into the cause of a lamp not doing its intended function, you may want to bear in mind the following extract from an article published in the Saturday Telegraph, 17 June 2006.

    "IT got so hot in the kitchen of an Italian restaurant in Carlisle that staff could almost imagine they were sunbathing. Indeed, some of them appeared to be developing impressive tans as they toiled over pizza and pasta dishes. But they also began to complain of sore eyes, blisters and blinding headaches.

    "When both chefs had to be treated in hospital for bums, the owner became alarmed and called in health and safety officials. For three weeks they made extensive tests and sent samples for analysis.

    "Finally the truth was revealed; Sun-bed bulbs had mistakenly been fitted to the electric insect traps intended to kill flies. 'All that time we were frying,' the owner said yesterday."

    My comment:

    I bet some strong words are being exchanged with the wholesaler which supplied the bulbs. But, there should be even stronger words exchanged with the inspectors for talking a whole three weeks to find the cause! This should have taken no more than a day!

    Let's continue ...

    Failing Incandescent Lamps  >>

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