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Topic Title: Metal halide lamps
Topic Summary: Premature failure
Created On: 10 August 2014 06:35 PM
Status: Post and Reply
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 10 August 2014 06:35 PM
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geov

Posts: 207
Joined: 22 February 2004

Hi all,
working in a garage showroom where they are complaining of early failure of 70w, G12 Mh lamps (many appear to be Osram PowerStar). Literaure suggests an average life of 15,000 hours for similar lamps. Typically they are on 7 days/week, 10am - 8pm and are served by three different circuits

The lamps are in iGuzzini fittings on Eutrac overhead tracks. Could a problem with the control gear lead to early failure of metal halide. I've had a look inside one of the fittings and visually all appears well.

Any ideas?
 10 August 2014 07:50 PM
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broadgage

Posts: 1359
Joined: 07 August 2007

Might be 220 volt copper iron control gear on our supply which is still 240 volts in practice most of the time in most places, worse still if it is actually 250 volts.

Do double check that 70 watt lamps are correct and not 150 watt ! they are MECHANICLY interchangeable, but not electrically.
I have seen 150 watt metal halide fittings labelled "MAXIMUM 150 WATT" Which could imply to a non technical person that lower wattage lamps such as 70 watt are also acceptable. This is not the case.

Edited: 10 August 2014 at 07:57 PM by broadgage
 10 August 2014 09:02 PM
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geov

Posts: 207
Joined: 22 February 2004

Good point about the wattage. The gear is marked for 220-240 & 70W on the fitting I removed, so I'm guessing the rest are the same.
Is there any form of testing I can carry out on the gear (which is Philips)?
Regards
 11 August 2014 11:25 AM
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davezawadi

Posts: 2817
Joined: 26 June 2002

How many hours do you think the lamps have done? I make that about 4 years to 50% failure (that is what average life means) and you should expect a noticeable number of failures after 2 years, particularly if the lamps and fittings are dusty so that the cooling is impaired. Powerstar lamps are usually quite reliable so you need to think about conditions carefully. It is unlikely to be excessive voltage to the fittings. You will notice a huge improvement in light output if you change the lot at about 10,000 hours, and very few failures at that time with a cleaning / relamp maintenance visit.

-------------------------
David
CEng etc, don't ask, its a result not a question!
 11 August 2014 04:19 PM
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geov

Posts: 207
Joined: 22 February 2004

Thanks David. It's been difficult to get anything more precise than "they are failing more quickly than they used to"! Given all the fittings are on tracks, suspended about three meters from floor level and are relatively (and surprisingly) dust free and that there's masses of free space/air around & above them, I don't think that impaired cooling is the problem.

Given the feedback, think I will arrange to change all the lamps on one track and monitor myself.

Cheers.
 11 August 2014 06:06 PM
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weirdbeard

Posts: 1652
Joined: 26 September 2011

Sadly you can only earn kudos for trying to repair stuff these days - tell 'em they've had it and then sell them some new fittings £££
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