With no tubes, the inputs of a magnetic dual F40 ballast
should show 13 ohms. Thanks to inductance, the ballast
without tubes should draw only 1/3 amp at 120 VAC.

That sounds like 40 watts, but in fact the power should be
negligible because with no load on the transformer, current
should lag voltage by almost 90 degrees. In the past I have
been curious enough about such things to shut off everything
in the house except some incandescent bulbs, time the wheel on
the service-entrance meter to see how many rpms per kilowatt,
then time the wheel to measure the power consumption of a device.

(If somebody could tell me how to read the specs on a power
meter and determine how fast the wheel should turn per watt, I
wouldn't have to play with light bulbs.)

I like the idea of installing a switch. If I were going to
use four tubes, I'd use two fixtures. I'd get the kind that
throw light to the sides and paint my walls a light shade.
That way I could have plenty of light without its seeming harsh.

Joe Fabeitz wrote:

Removing both bulbs on a ballast will cause that circuit to draw ZERO
current. The traditional ballast places an inductive resistance in series
with each tube to limit the current when the tube is illluminated. Removing
the tubes breaks the series circuit. The newer electronic ballasts will
draw a small amount of current (less that 1/10 amp) even with the tubes
removed.

BTW, why do you some of you guys feel compelled to respond to these
questions even when you don't know the answer? You typically begin your
post with "...I don't know much about this but....." Why not shut up and
learn from others?

"Walter R." wrote in message
...
My kitchen ceiling has 4 light fixtures with 2 fluorescent lights in each
of them (T-12 4' long). This is too bright and wastes energy.

I would like to deactivate 2 of the fixtures. Can I just pull the 2 tubes
out of 2 fixtures, but leave these fixtures (with the ballast) connected
to the house wiring?

Would this damage the ballast? Would the fixtures, with the ballast but
without the tubes, still draw power? Or, should I disconnect the wires to
the fixtures (more trouble because I have to open the fixtures)?

Thank you

--
Walter
www.rationality.net
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