From: Mike Poulton
Subject: Re: Running high power mercury vapour lights at low power.
Date: 16 Sep 2002 00:01:09 GMT
Organization: MTP Technologies
On 15 Sep 2002, Ian Stirling said:
> I have several 400W streetlights, that I'd like to use as biocidal UV
> After the outer envelope is removed, should it be possible to simply
> run it at 5% power simply by reducing the current? (I know the voltage
> will rise)
> (I have used it as a source to expose PCBs, but it's slight overkill
> :) )
> I am aware that it's not a good idea to look at this sort of UV, it'll
> be totally enclosed when operating, with adequate interlocks.
> Is the life likely to be much extended, compared to running at nominal
The life will be very much reduced (possibly to minutes, or a few
hours). The lamps rely on high internal pressure and high wall
temperature to prevent vaporization of the electrodes and condensation
onto the tube. Additionally, they will have mostly an argon spectrum
unless they get sufficiently hot to vaporize the mercury. This isn't to
say it won't work -- it will light up and produce some UV, but it's very
hard on the bulb and won't be very bright. I would suggest using a 175W
bulb and balast from a residential floodlight. You can get them for
about $60 at Lowe's. Just break the envelope carefully and use it as
the UV source. Make SURe you are not exposed to the light. It is not
just UV, it's UVC and vacuum UV -- down to 194nm and shorter! It causes
painful radiation burns, serious eye damage, and really promotes skin
cancer. It also produces ozone, which needs to be removed by
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