Message from discussion
TOT halogen efficiency
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NNTP-Posting-Date: Fri, 03 Jul 2009 15:31:57 -0500
Date: Fri, 03 Jul 2009 21:31:58 +0100
From: Andy Champ <no....@nospam.invalid>
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Subject: Re: TOT halogen efficiency
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Bill Wright wrote:
> 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
> 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,
> 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
> relatively under-run, will last longer.
>
> I reduced the voltage on the 12V lamp until it had the same apparent
> 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
> more efficient? If so, why?
>
The guys over on uk d-iyy will be able to pick this one up. This is a
frequent topic.
Ignore any references to angle grinders.
Andy
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