my lamps keep blowing...

[Dan Appleby]

Hello,

 

first and foremost... I'm not really a lampie, so please excuse any ignorance!

 

We have a simple lighting rig in an install we put in some time ago - 24 PAR 64's, and 12 Profiles...

 

Just recently (the last few months) the rig has started blowing an unusally high number of lamps - 5 or 6 have needed new lamps in 3 months. The install is a church, so they are used 2 - 3 times a week, usually for no more than 4 or 5 hours at a time.

 

My initial thought is that we had a dodgy batch of lamps - just wondered if anyone had any other ideas...?

 

Cheers,

Dan.

[Just Some Bloke]

Here's a thought:

 

All the lamps were from the same original batch, thus were all made at the same time and to the same specifications. Thus, you'd kinda expect them all to have about the same lifespan.

 

Personally, I'd be surprised if they didn't all fail within 3-4 months of each other.

[gareth]

A dodgy lamp batch is one possible explanation. However, you don't say exactly how long ago you put the gear in. As JSB says, in a situation like yours (all lamps were new at the same time, and are all used on a similar 'duty cycle') you'd expect the lamps to all start popping at around the same time - so as long as "some time ago" isn't too recent, then what you're experiencing is probably nothing to be concerned about. Lamps are consumable items, after all - you can't expect them to last for ever.

 

Just to rule it out, it might be worth making a couple of measurements of the mains voltage in your church, just to make sure it isn't unusually high - your lamps will be rated at 240v so in an ideal world they don't want to be seeing any more than that, but the trouble is that UK spec is 230v, +10%/-6%, so anything up to 253v coming out of the wall would be considered 'normal' by the electricity board even though it's detrimental to the life of your lamps (Bryson will no doubt tell you all about that!).

[Ekij]

Just a thought ... you say the install is a Church, the sanctuary or a hall?

Vibration might be an issue if the lamps are being used to illuminate a hall when youth groups are doing activities. Some of the church halls can shake quite a bit when 40 or so teenagers are thumping about, perhaps they were outside in the better weather but now it's got a bit :( they are inside?

[peter]

Does the hall get particularly cold at night time, and are the lamps snapped to full on power up? Perhaps you should consider pre-heating the lamps during the winter, even at night time? Or slowly fading them up to the required level, to reduce the filament stress on power up?

[MarcT]

Hi Dan,

 

You probably know this already, but just in case - be careful not to touch the glass envelope of the replacement when changing a halogen lamp.

If you do accidentally touch the glass, carefully wipe it with a cloth & some white spirit as below.

 

Not a problem with your PAR lamps, since the quartz crystal lamp is fully enclosed by the outer glass & reflector.

 

Handling

Fingerprints on the glass burn in at operating temperatures (200 degrees Centigrade to 600 degrees Centigrade) causing the glass to recrystallize in a few hours to an opaque and milky form with less strength. Glass can be cleaned with cloth and alcohol.

(From Tungsten Halogen Lamps)

 

Best Regards,

Marc

[Tomo]

A PAR64 lamp is only expected to last for about 300 hours of use, so I'd expect to be changing the lamps every 20-30 weeks or so at your usage.

 

If they all get similar use, that would mean them all going fairly close to each other.

 

300 hours is not an exact lifetime though - it's calculated from a big test batch and is the time when ~50% of them have died.

 

Lifetime calculations are complex though, and minor variations in power supply can have a very large effect on lamp life.

[David A]

You can work back how many hours the lamps have run as you should get around 400 hours or check the specification for the lamps, if you are slightly overvoltage then running your dimmers at a lower level will greatly increase the life but don't overdo it or you will lose colour temperature and use power inefficiently, as noted vibration particularly during focusing is a major killer of lamps.Ignore the preheating advice this is an old wives tale.Check that the lamps are burning the right way up, I often come across them upside down and the heat rises into the base and the seal breaks letting the vacuum out.Finally when you change lamps always look at the pins, if there is any burning your base is stuffed so do not put another lamp in until you have changed the base, I have come across a lot of bad bases recently.

[Bryson]

*The whole of the below is written while touching a large bit of wood....*

 

In my venue, I get 253v out of the wall, and thus my lamp lives are absolutely shocking. However, I've had a fair bit of success reducing the damage by:

Changing all my 1.2k T29s to 1k T11s

Simply changing the "on" button on the 300 to bring stuff to 90%, not full.

Rarely using that extra 10% unless I really, really need it.

 

Having said all of that, 5 or 6 in three months. IE: 2 lamps a month out of 36 sounds about normal. Maybe slightly high, but nothing to worry about.

[Johnno]

... Check that the lamps are burning the right way up, I often come across them upside down and the heat rises into the base and the seal breaks letting the vacuum out...

 

OT: Given that a vacuum is the absence of everything what gets out? :(

[David A]

Sorry shouldn't have attempted humour on such a sad day.

[niclights]

A PAR64 lamp is only expected to last for about 300 hours of use, so I'd expect to be changing the lamps every 20-30 weeks or so at your usage.

 

Though this is theoretical and there are many factors, personally I find my CP61/62's last far longer than that. Well into the years for some and that is almost daily use in hot, high vibration environment and combination of dynamic (mainly 61's) and static @ 100% (62's).

 

Based on this my instinct is most likely bad batch, high voltage or snapping on from cold without preheat.

[Don Allen]

You haven't mentioned what your PAR64's are if they are 240 volt then you will only get about 300 hours, if you can go to 110 volt pairs, then you will get about 2000 hours http://www.gelighting.com.ar/App_Lib/docum...heet_ingles.pdf

 

Using the top set of your dimmers if available to set your max volts to 95 percent will lengthen life, or use your desk as others have mentioned. Most Jands dimmer racks have mains regulation built in so a fluctuation of input mains volts will not go through to the output, very few other brands of dimmers seem to offer this feature.

 

Do you have any reactive loads such as air conditioners or freezers on the same distribution circuits as they may cause a spike. The only way to really check this is to put a voltage recorder across the supply circuit to monitor it over a week or so.

[RODALCO]

Most things are already mentioned.

 

Have you considered putting a hourmeter on the lamp circuit to check how many hours they are actually used.

Who knows, the lamps may get more use than you think or are left on unnecessarily.

 

I use hour meters a lot to check on streetlight circuits and hotwater pilots in the poco industry.

 

edited for typo's

[Ken Lovelace]

I had the same problem in one of the venues I work at. We started having unusually high lamp failure and this went on for six months or so. Finally did some research and found the cleaning crew would turn them on at night and use them to clean by. They were left on for over 4 hours, 3 times a week. This really cut into the lamp life. After having a conversation with them about this, ever thing went back to normal. I would try what RODALCO suggest and see if there is any unauthorised use of the equipment.