Lamps and Incense

[cedd]

Hi all

 

Mrs Cedd works as a youth worker in a Catholic retreat centre. They have a small chapel that seats around 40. It's a really beautiful, newly (ish) built space. Elements of the room (statues, the cross, etc.) are lit with what appear to be 500W fresnels, though until I can get some scaffolding I can't be sure of the lamps used - this is purely a Mk1 eyeball from the floor.

 

I haven't actually seen the dimming arrangement yet, but I know that the lamps are normally run dimmed and the dimmer is the only normal way of switching these lamps on or off. They provide the bulk of the lighting within the room as the space is often quite dimly lit.

 

They're suffering what they believe to be a high lamp failure rate. I suspect that it's actually no higher than you'd expect for these lamps and they're simply more used to the lifespan of domestic lamps and fluorescent tubes which light the rest of the building. The Priest has come to the conclusion that it's the large amount of Incense that gets burnt in the room that must be the cause (residue on the lamps or something like that!) and has therefore stopped using the stuff. I don't agree with his reasoning and simply think that they're using the wrong lamps and fixtures for the job.

 

So I've got a few questions;

Do people think I'm right in ignoring the incense as being the cause - I can't see it being much different to haze?

 

Do you agree that with (assumed to be) 500W fresnels, often run dimmed and being switched on and off using a dimmer quite regularly, they can expect a much reduced lamp life compared to domestic lamps?

 

Can folks suggest a solution to the problem? I can't go as far as starting again, and the dimmers are fixed and need to remain (no budget to replace and they still need to be able to dim whatever I put up for them). I'm thinking that a lower rated lamp might be a good start - seems inefficient to be running them constantly dimmed. Are there any direct LED replacements yet that can handle being externally dimmed or is that a pipe dream? Access to change lamps is tricky, requiring a scaffolding at the very least. Longer lamp life is the holy grail! Ideally without changing the lanterns themselves.

 

Any help much appreciated!

 

C

 

 

 

 

 

[Ashley R]

I would be checking if the lamps that have been fitted are possibly 220/230V varieties, instead of 240V. If they have been installed correctly (i.e. no greasy fingerprints on the lamps)

 

A trusty T27, has a rated life of approx 600 hours if I recall correctly?

 

If those kinds of hours are not good enough, if they want to stick to tungsten, maybe say ye olde par 56's with WFL lamps and diffusion? as par 56 lamps have a 2 or 3000 hour life span! and are cheap as chips

[boatman]

Change the T27s for M40s. A much lower colour temperature but a lamp life similar to d0mest1c lamps.

[alistermorton]

Change the T27s for M40s. A much lower colour temperature but a lamp life similar to d0mest1c lamps.

 

If they are T27 lamps. Which, given the estimate of 500W sounds unlikely. Might be CP82 ...

 

But you never know.

 

I'd guess the change to a PAR solution would actually work quite well, unless they need the beam focus of a fres.

[Jivemaster]

Halogen lamps respond BADLY to being run dimmed for long sessions, the halogen doesn't recycle the evaporated tungsten as it should at full temperature. They NEED a run at full power to get the envelope hot enough to cause the halogen to recycle the tungsten back to the filament -even a run of 10 minutes at full power will usually restore the halogen/tungsten cycle and deposit the tungsten back onto the filament.

 

Tungsten lamps give longer service run 20% or more below rated power.

 

In long run operation the biggest causes of poor life are clogged vents and burned connectors, Maybe there is something in the incense theory but it's not everything. "I can't see it being much different to haze?" Have you ever seen inside a moving head light in a haze filled nightclub All the surfaces get a fur coat.

 

Are you planning to get access and do the job? Once you have the lamp type you can establish the manufacturer's rated life and see how it compares with what you have in practise.

[Don Allen]

The lack of a halogen refreshment cycle is also my guess for the high failure rate.

 

Can you go to using PAR16 running at full for a similar light level to what you were getting from the 500W fresnels. I did this at a church, where we replaced 150W PAR38 with PAR16's as there is a wider selection of beam angles from PAR16's which will overcome the loss of the Fresnel variable beam width.

[adam2]

It might be high mains voltage.

 

The legal upper limit is 253 volts, and that will noticeably reduce lamp life.

 

Or has already been suggested it might be 220 be 230 volt lamps on our supply which is still 240/250 most of the time in most places.

 

 

 

[Jivemaster]

Greasy fingerprints cause a Halogen capsule to break before the filament blows, so would incense damage to the quartz envelope, You would see white powder tungsten oxide around the smashed lamp pinch. Burned contacts in the lamp holder usually show themselves only by the matching burns on the lamp pins -once the holder is burned it burns the pins of ALL the lamps used as replacements, the filament is intact but there will be no pin where the burned holder has arced the metal away.

[cedd]

Great, that's been really helpful!

 

I'm going to head up there in the next few days, if I can get hold of some scaffolding. I'll take a close look at the lamps currently in use and also whack a DVM over the mains. There are a couple of dead lamps currently so hopefully they'll yield some helpful evidence.

 

 

 

 

Pars may well be the way forward. The current fresnels are using barn doors but I don't know how much they're actually being used. If they're wide open then pars might be a good way forward. If they're going to give increased lamp life then the cost of the can Vs the faff of erecting scaffolding seems to be a good trade off.

 

Cheers

 

Chris

 

 

 

 

 

[timsabre]

There are some good retail-type led fixtures available which I would consider over pars, which would still be a maintenance liability. In my other life I advise on church lighting schemes and a lot of churches are fitting led because it is pretty much zero maintenance and also offers some power saving.

 

The Concord Beacon fixture is worth looking at and so are some of Illuma's products. Attractive looking fixtures with tight beam control.

[musht]

often run dimmed and being switched on and off using a dimmer quite regularly, they can expect a much reduced lamp life compared to domestic lamps?

 

Dimming lamps and soft starting them should massively extend their life, unless dimmer pukes at startup with a flash and have abnormally high mains V. On dim even high V should average out lower.

 

Some discussion about whether dimmed halogen needs a clean up cycle, in reality no examples of blackened lamps caused by underrunning ever seem to appear.

 

How many hours a day is the facilty open and is there any other users, like cleaners, who whack everything to full for extended periods?

 

Sources of vibration getting transmitted to the mountings, HVAC or similar.

[Simon Lewis]

Cedd,

 

Although all of the technical issues cited here may be having an impact on lamp life, I strongly suspect that the simple answer is your first one - they are used to fluorescents and even halogens lasting between a year and five years (MR10s excepted of course!). Something that goes after a few months use must obviously be faulty....

 

 

I'd echo the call for changing to lamps that last a few thousand hours but can be dimmed with existing technology!

 

Simon