On 12/6/2010 10:50 AM, Bill wrote:
Someone suggested (I could not locate the post) that if I wanted quiet
fluorescent lights, then I should look for those with an "A" rating.

Putting that detail aside temporarily. What would be the practical
differences between a "standard electronic ballast with 20 THD"
and an "instant on electronic ballast with 10 THD"?

Bill

Trying, usually, to answer questions for myself before and after I post,
I ran across the following tidbit. It isn't that helpful though. BTW, I
have no reason to believe THD is accumulated if fixtures are wired in a
series, but I would certainly be interested in knowing if anything of
that nature is true.


THD stands for Total Harmonic Distortion. The distortion is feedback
caused by deviation from the sinusoidal waveform. The industry standard
is less than 20%. If the THD is very high (around 150%), an electrical
fire can occur. Magnetic ballast run 90%-120% THD.

The information above was copied from :
http://www.ace-ballast.com/articles/...last_Questions

Bill