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Re: Ballasts for flourescent lights

Diana Berberich asks some excellent questions:
<fishfaceid at yahoo_com>
>      How does a ballast "know" if it is driving a
> florescent tube or compact tubes like I have from AH
> Supply?  

Short answer is, it doesn't; it isn't sentient!  Nor do they have
detectors.  Different lamps will present different resistance to the
flow and the a higher resistance will cause a great voltage drop across
the the bulb.  A circuit could be used to detect that, but it probalby
wouldn't be enough info to decide how to change the ballast.  Dollars
to donuts they don't have any such thing in the electronic ballasts.  I
know the marketing sounds like the ballasts change depending on the
bulb as if they intelligiently adapt via voltage servos, invisible
fields, or gosh knows what -- but if you listen closely, or read
closely.  They don't say anything not consistent with the
one-valve-one-position description:   A ballast is sort of like a valve
on a hose; it provides a certain amount of restriction but it doesn't
know what nozzle is on the end of the line.

> I replaced an old burned out ballast with an
> electronic ballast called the UltraLux which has some
> nice features.  I can use 4, 24 inch tubes up to 4, 96
> inch tubes and the ballast supposedly adjusts to drive
> them.  I am not an electrical wizard by any means. But
> here is what they say on their web site:
> http://www.fullspectrumsolutions.com/UltraLux-Ballast.htm
>    Operates any combination of lamps (T5, T8, T10, and
> T12)
>    Operates 1 to 4 lamps both 1 & 2 lamp or 3 & 4 lamp
> 120V, 50/60Hz

Yes, they light and stay lit.

>    Will work on lower voltage systems and is not
> affected by brown outs.  
>    Operates as rapid start or instant start
well it does one or the other, but it will light either kind of bulb. 
See Waynes' posts about the chronic wear mismatching causes.  NOt
something you'll probably see with 12 hour cycles.

>    Operates multiple lamps from 25 up to 50 watts
> (F20, F25, F30, F32, F40, F60 lamps) (2', 3', 4', 5'
> lengths) 

You can put lots of different nozzles on your hose and the water
waters, the nozzles wets, etc.

Ballasts don't adjust how much current goes through a flourescent bulb,
*you* do when you choose the ballast.  Different ballasts are like
different size water valves.  Different bulbs will add a little to the
equation (different resistance will allow more or less current to flow)
but basically ballasts are like valves water valves with just one

>    And it's *dimmable down to 50% light level with an
> inexpensive dimmer!
>    I did call them and speak to them and got answers
> that made me feel that this might solve my problems. 
> I am pleased with it driving my 4, 36 inch tubes.  But
> I would like to convert or add some 36 watt or 55watt
> compact florescents (the double tubed jobs).  Is there
> any reason to believe that this ballast or any other
> ballast that is designed for single tubes should not
> be appropriate to drive compact florescents?  I have
> asked this question before but never got an answer
> from anyone.
> Thanks, Diana

I'll go out on a non-engineer's limb here and say, No, no reason.  Then
I'll add a littel wiggle room and say this:  If you match the watts,
give or take about 10%, and the ballast will light the bulbs at all,
then you can go ahead and run them.  If the bulbs seem abnormally hot
or blacken at the bulb ends too quickly, they will be aging more
quickly than otherwise.  You can live with that or get a fan and cool
the bulb down-- that will help.  The too hot syndrome usually occurs
only when you are overdriving your bulbs.  The blacken comes from keep
the filaments hot and excited.  Some folks don't care; they use cheaper
bulbs, overdrive them like crazy; toss 'em out and replace.  Live
bright and die young.

Hope that helps,
Scott H.

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