dimming a floodlight

[DoctorStar]

....that I don't know the answer to.

 

I have bought a cheap £4.99 500W Flood from a well know DIY shop with a view to using it as dimmable houselighting in the school hall. Then I had a moment of doubt....can I attach such a fixture to a dimmable source?

It has a 500W linear halogen bulb.

 

Thanks in advance,

 

DocStar

[J Pearce]

A 500W halogen lamp will be fine on a dimmer.

 

You may wish to consider the wisdom of using a lantern designed for outdoor use indoors though. Check the usage guidelines and have a good excuse for not following them if it says 'outdoor use only'.

[brianeades]

Hi

We use them in our venue,eight in total problem is they are screwed to the beams across the ceiling as there not much air space they tend to blow lamps due to heat build up.these were only put up as a tempory measure ha ha

 

Brian Eades :** laughs out loud **:

[csg]

whilst you may well be right about the lack of air space, if you were using the supplied lamps you get with these fittings they never seem to last very long in my experience - much better fitting philips etc from new

 

I see these installed all over the space, and so long as clearance distances from lit / flamable surfaces is maintained, I cant see a problem using them indoors, and yes they are perfectly fine being dimmed.

[dmxtothemax]

....that I don't know the answer to.

 

I have bought a cheap £4.99 500W Flood from a well know DIY shop with a view to using it as dimmable houselighting in the school hall. Then I had a moment of doubt....can I attach such a fixture to a dimmable source?

It has a 500W linear halogen bulb.

 

Thanks in advance,

 

DocStar

 

I use these same linear tunsten halogen lights in my church light rig,

Yes they most definately do dim with no problems,

There is a myth around that running halogen lamps at less than full output can interfere with the

process of halogen recycling in the tube, however I have found that in real life it is not a problem.

The main problem is most lamps are poor quality, usually cheap chinese origin.

I found a brand called NELSON with quoted life of 2500 hrs, these lamps do last much longer than the cheapies,

Even the so called name brands seem to suffer from short life, maybe they source them from china.

Experiment with different brands and see which lasts longest. YOU MUST FIND GOOD QUALITY LAMPS!

It took me a while to find a method of color filter attachment that didnt burn the gels, but I did get it right with some experimenting.

These lights do run quite hot thou, but its normal, so be sure they get some air flow.

And dont forget to check that the lamp contacts dont get dirty or burn, up its a common

problem with these lights, but the contacts are easily cleaned.

I use about 12 of these lights for general color wash.

And you can use lower wattage lamps if heat is a problem, try 300w lamps.

As I am in a different country to you, you might not be familiur with the brand NELSON but if you ask

around in your area you will find out which lasts best.

[DoctorStar]

Cheers Folks....all points duly noted.

 

Have a good day.

 

DocStar

[Brian]

The main problem is most lamps are poor quality, usually cheap chinese origin.

I found a brand called NELSON with quoted life of 2500 hrs, these lamps do last much longer than the cheapies,

 

Long life lamps last longer because the filaments in them are underrun giving less light out. If access is a problem then they are a good idea. Also, in the UK, make sure you are buying genuine 240V lamps.

[Thirdtap]

Hello I have had the problems of 500w enclosed floodlights not lasting that long and we changed the lamps to to lower rated versions 300 watts worked quite well for us.

[TomHoward]

We have a load of the 150W variants from a well know catalogue building supplier that we use for work lights or practicals on sets - as said they are cheap and cheeful but they eat gel, haven't found a reliable way of attaching it without it melting yet.

[powersolve]

I've done something similar at a church, but found that the lamp contacts burned out pretty quickly - clearly either very poor quality, or getting very hot - or maybe a combination. We replaced the lights with little 500w floods from Thomann (here) which are great. Not too expensive (£40 - admittedly quite a bit more than your £5 - and I recognise that you've already purchased yours anyway), and they have quite a well defined beam spread, with not too much spill. You can get barn-doors for them too, and they are designed to be gelled without difficulty, although we've never tried it. I suspect they'd eat gel pretty quick. Lamp life is fine, though.

[Brian]

I suspect they'd eat gel pretty quick.

They do. I had some of the 3-way units and darker colours would last about one 2-hour show!

[boatman]

I remembered seeing a thread about gelling 500W floods on here about two years ago. After a quick search I found it:

 

Link

 

The adaptor may need to be tailored to a particular type of 500W fitting, but should be within the capabilities of a small metal bashing workshop with a spot welder.

[kitlane]

There is a myth around that running halogen lamps at less than full output can interfere with the

process of halogen recycling in the tube, however I have found that in real life it is not a problem.

 

Recycling the halogen is not the issue. It's the tungsten we want to recycle. For the Tungsten Halogen Cycle to work the temperature of the glass envelope must be at least 250 degrees Centigrade. or thereabouts. Anything less and the tungsten oxyhalide molecules will dissasociate and tungsten will be deposited on the glass causing lamp blackening. It's reversible though, just run the lamp at full temperature for a while.

 

In real life it may be that you haven't run the lamps this cool for any length of time and/or have always run them hot enough thereafter, but the mechanism is not a myth.