🚀 go-pugleaf

Klaus Vestergaard Kragelund wrote:
> "Paul Bealing" <paul@pmb.co.nz> wrote in message
> news:TINca.5877$8b.679066@news02.tsnz.net...
> 
>>DaveC wrote:
>>
>>>I've been asked to help light a small office building hallway. The
>>>fluorescent lamps are way too harsh for the office workers, and the
>>
> tenants
> 
>>>favor the overhead QH approach.
>>>
>>>I've looked at the local home centers' lighting departments and see
>>
> quite a
> 
>>>selection of LV systems using overhead steel cable with 3 hanging
>>
> reflector
> 
>>>bulbs (with a choice of trim, or not) tapped in at appropriate
>>
> intervals.
> 
>>>Price for the above from $70-100us.
>>>
>>>Being encouraged by what I saw, I decided to see what I could build from
>>>scratch.
>>>
>>>As you probably can guess, I'm running into current supply/demand
>>>limitations. Each of the 2 hallways could use about 15 lamps. Lamps are
>>>available in 20 and 50w versions, which at 12v, draw approximately 1.7a
>>
> and
> 
>>>4.2a, respectively. I now see why the cost of such a system is mostly
>>
> for the
> 
>>>supply.
>>>
>>>Looking for a ready-made 12v supply, I find this at Jameco for $70us
>>
> that
> 
>>>provides 12.5a:
>>>
>>><http://www.jameco.com/cgi-
>>>
>>
> bin/ncommerce3/ExecMacro/Jameco/searchResult.d2w/report?sort=BPA&search=1234
> 22
> 
>>>
>>>This would allow me to run 7 of the 20w lamps, or only 2 of the 50w
>>
> lamps.
> 
>>>I can't see buying 2 supplies to run the 15 (well, I guess we could rev
>>
> that
> 
>>>to 14) lamps in each hall. I seem to be butting up against Ohm's Law.
>>>
>>>Maybe build a simple, unreg'd, analog power supply with massive
>>
> transformer
> 
>>>and rectifiers for 30A?
>>>
>>>Any other ideas (or links to sites) to help me reach a solution would be
>>>greatly appreciated.
>>>
>>>Thanks,
>>
>>I agree with another post; there will be a considerable power waste
>>using QH over Fluro.
>>
>>Remove a few fluro tubes and/or change the rest to a softer colour.
>>
>>My biggest concern would be the fire risk from all those QH lamps and
>>the transformer. How close is the wooden ceiling to the lamps?
>>
>>I have found that most QH transformers put out 11 to 11.5 volts. If you
>>run QH lamps at even slightly more than 12 volts the lamp life will be
>>reduced. Most QH lamps already fail well before they should.
>>
>>I quite like the ease of dimming of QH lamps, but I don't like the high
>>heat output, energy consumption and short lamp life when compared to
>>fluorescent.
>>
> 
> 
> Buy lamps with greater power rating and reduce the voltage. This will give
> you way longer lifetimes if you can live with the more "warm" spectrum of
> light they emmit when driven this way.
> 
> Cheers
> 
> Klaus
> 
> 
We have operated lamps at less than 100% and with a soft-start to reduce 
initial shock. Experience over the past 6 years has indicated that the 
failure rate has still been higher than expected.

If you run a QH at much less than 100% for long it develops a black 
coating on the inside. QH require periodic full power operation to raise 
the temperature and restore the deposited tungsten to the filament.

Paul Bealing