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Newsgroups: uk.tech.digital-tv, uk.d-i-y
From: NT <meow2...@care2.com>
Date: Fri, 3 Jul 2009 14:08:01 -0700 (PDT)
Local: Fri 3 July 2009 22:08
Subject: Re: TOT halogen efficiency
On Jul 3, 9:31 pm, Andy Champ <no....@nospam.invalid> wrote:
> Bill Wright wrote: partly because theyre (mostly) used in downlighters. > > Some time ago I reported in this hallowed forum my disapointment at the > > apparent inefficiency of some mains voltage halogen downlights I'd fitted in > > the dining room. Based on the 12V halogens I have used elsewhere I expected > > the room would need eight 25 watt lamps. In fact it needed eight 50W ones. > > 400W to light a medium sized room! > > I'm now intending to put new lights in the kitchen. Today I lit a 12V 20W performance on 12v ac is identical to on 12v dc > > lamp and a 240V 25W lamp side by side. Both lamps were the 36deg type. The > > 12V lamp was much brighter. I was running it on 12.00VDC, but the current > > drawn was 1.7A which equates to 20.4W, so I guess the brightness would be > > the same on a nominal 12V AC supply. > The 12V lamp had a neutral colour, yes, mains ones generally run at lower filament temp > > whereas the mains lamp was rather warm. I wonder if this accounts for the > > greater efficiency of the 12V lamp, > and means that the mains lamp, being quite the contrary. Mains have very thin filaments, so they need to > > relatively under-run, will last longer. underrun them to get them to last adequately. > > I reduced the voltage on the 12V lamp until it had the same apparent yes, thicker filament enables higher operating temp for same life > > brightness as the mains lamp. At 8.7V both lamps had the same brightness and > > colour temperature, as near as I could tell. > > Can anyone cast any light (geddit?) on this? Are 12V lamps really so much > The guys over on uk d-iyy will be able to pick this one up. This is a more info on halogens, downlighting, dimming, and bulb life here: > frequent topic. http://www.wiki.diyfaq.org.uk/index.php?title=Category:Lighting > Ignore any references to angle grinders. NT > Andy You must Sign in before you can post messages.
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