[DSLF] Digest Number 1768

[DarkSky-list@yahoogroups...]

There are 2 messages in this issue.

Topics in this digest:

      1. Re: Digest Number 1767
           From: Jack Liebenthal <jackl@tetontel...>
      2. Re: Digest Number 1767
           From: "Terry McGowan" <lighting@ieee...>


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Message: 1         
   Date: Tue, 04 Oct 2005 21:46:06 -0600
   From: Jack Liebenthal <jackl@tetontel...>
Subject: Re: Digest Number 1767

At 03:22 PM 10/4/2005, Greg Furtman wrote:
>And the newer style "twisty" bulbs start up even
>when it's cold, although at 0 degrees F it takes them a minute or two to get
>up to full output.


Some years back, there was a discussion here about CFLs and cold 
startup.  Yellowstone Park folks say they never fail to start, and it 
gets well below -20F there.


Teton Dark Skies -- Seeking to preserve the natural features of Teton 
Valley nights
<http://home.silverstar.com/~jackl/tdsbasic.html>http://home.silverstar.com/~jackl/tdsbasic.<http://home.silverstar.com/~jackl/tdsbasic.html>html

I often think that the night is more alive and more richly colored 
than the day.  ~Vincent Van Gogh






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Message: 2         
   Date: Wed, 5 Oct 2005 10:18:26 -0400
   From: "Terry McGowan" <lighting@ieee...>
Subject: Re: Digest Number 1767


----- Original Message ----- 
From: "Jack Liebenthal" <jackl@tetontel...>
To: <DarkSky-list@yahoogroups...>
Sent: Tuesday, October 04, 2005 11:46 PM
Subject: Re: [DSLF] Digest Number 1767


> At 03:22 PM 10/4/2005, Greg Furtman wrote:
>>And the newer style "twisty" bulbs start up even
>>when it's cold, although at 0 degrees F it takes them a minute or two to 
>>get
>>up to full output.
>
>
> Some years back, there was a discussion here about CFLs and cold
> startup.  Yellowstone Park folks say they never fail to start, and it
> gets well below -20F there.
>
>
> Teton Dark Skies -- Seeking to preserve the natural features of Teton
> Valley nights

There's always been some confusion about what the low-temperature starting 
specifications for CFLs mean.  If the lamp specification is "0 degrees F", 
the lamp manufacturer  is not telling you that the lamp will always start at 
temperatures above zero and won't start at temperatures of zero and below. 
The lamps don't work that way.

What happens is that at a given temperature a certain percentage of lamps 
will start over a certain number of burning hours or the rated life of the 
lamp.  The manufacturers test their products to determine that percentage 
and that percentage sets the specification for a particular lamp design.

Below that specification temperature, you can expect fewer lamps to start 
within a given time; but some lamps will start immediately and some will 
start after a period of time assuming that the electricity remains on --  
perhaps as some heat builds up in the lamp from the ballast circuitry.

The percentage of lamps that start at any given temperature is also a 
function of how many hours the lamp has burned and the socket voltage.

So, for the Yellowstone Park situation, it's no surprise that the lamps 
start at -20F or even below.  The Park folks may not see the few lamps that 
don't come on right away and the lamps may not have burned long enough so 
that the number of lamps that don't start at those low temperatures is a 
significant number.

What is likely after a few thousand burning hours is that the number of 
lamps that never start or only start after a long period at low temperatures 
will increase to the point where they are noticed and the lamps will be 
changed.  But those lamps shouldn't be thrown away, they're fine with many 
more hours to burn.  Just install them someplace warmer.

What is certain is that if a lamp design does indeed meet a starting 
specification of -20F, the lamp manufacturer is sure to put that to good 
sales use by listing that minimum starting temperature in the sales and 
specification literature.   So, put a CFL lamp where you want to.  Enjoy the 
bonus if it starts at temperatures below its rating and put it somewhere 
else warmer if it doesn't start.  But don't count on the lamp starting below 
its rated temperature for the 10,000 hours (typical)  lamp life and don't 
worry about low temperatures harming the lamp.  The lamp doesn't care.

Terry McGowan







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