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Re: GBlist: Fluorescent Lights: off or on?



Your question is related to one of the great urban myths of our time. 
That myth being, "We use more electricity turning a light on and off than
just leaving it on."

This myth got started (who knows where) because when we turn on any
electrical appliance we add an extra load to an electric grid.  The added
load is like a vacuum that invites electron activity or electricity to
rush in.  As you know, nature hates a vacuum, and that is precisely what
the electricity does is rush in and create electric vibrations in the
device we wish to use.

This is called a peak inrush. The initial rush of electricity can be
quite large and violent.   It can blow open incandescent filaments.   But
it is very brief (microseconds) and is more pressure than force. After
inrush a balance and a regular current  flow is achieved and we see work
as light or motion.

If you are purchasing power from the power company your concern should be
that you purchase power by the kilowatt hour ($0.10 is typical).  This is
a measurement of supply based on time.   There are no additional charges
for the peak inrush.  You will realize the greatest savings when you use
an electrical appliance with the lowest power requirements for the
smallest period of time .

If you are producing your own power with a solar, wind or water
generating system then you may not care about peak inrush or how much
time you use a electrical appliance as long as you don't exceed your
system capacity.

Regarding fluorescent lighting, as with most products the newer products
tend to be more efficient than older products.  You can compare the
claimed efficiency by determining the product's voltage and current
requirements.  This should be labeled on any electrical appliance.  

The electronic ballast tend to be somewhat more efficient because they
are not as dependent upon the peak inrush to get them started.  They
build up a charge to get them started.  The ultimate factor is the
electrical requirements of the products on the load.


On Fri, 26 Sep 1997 11:20:47 -0400 liverjx@nu.com writes:
>
>With the goal of optimally operating a "green building" once the 
>occupants
>have arrived, I have a question regarding fluorescent lighting.  Does
>anybody know how the startup ballast energy requirements of a 
>fluorescent
>fixutre relate to the amount of energy saved by turning the fixture 
>off for
>a period of time?  Or in other words, if one is leaving their office 
>for
>1/2 hour, does it make "energy sense" to turn off the fluorescent 
>lights or
>leave them on?  And what is the threshold time period where it no 
>longer
>makes "energy sense" to turn the lights off.
>
>I would imagine that the time period depends somewhat on whether the
>ballast is magnetic or electronic.  If anybody has any insight into 
>this
>commonly asked question, I welcome your input.  Thank you.
>
>John Livermore
><liverjx@nu.com>
>
>
>______________________________________________________________________
>This greenbuilding dialogue is sponsored by CREST <www.crest.org>
>Environmental Building News <www.ebuild.com> and Oikos <www.oikos.com>
>For  instructions send  e-mail to  greenbuilding-request@crest.org.
>______________________________________________________________________
>
______________________________________________________________________
This greenbuilding dialogue is sponsored by CREST <www.crest.org>
Environmental Building News <www.ebuild.com> and Oikos <www.oikos.com>
For  instructions send  e-mail to  greenbuilding-request@crest.org.
______________________________________________________________________


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