On Mon, 14 Mar 2005 00:45:56 GMT, "James Sweet"
wrote:



They do, and they were quite common at one time. One other advantage they
have is that they lack separate windings providing continuous power to
the
filaments in the tubes so the total power consumption is several watts
lower.

The power savings is perhaps 1 watt per lamp and perhaps another watt
in the ballast. The downside is much shorter lamp life. Rapid Start
ballasts are by far the most common type of EM ballast use for 4-foot
fluorescent lamps in the US.



From what I've read, it's more like 3-6 watts per lamp, which if you're
talking 500 lamps in a decent sized building can be somewhat significant.

The power consumption in each electrode of a normal current rapid
start lamps is 1 watt, or 2 watts per lamp. When you remove external
electrode heat the arc voltage increases slightly and the net arc
power increases by 1 watt for the same current. So, the net power
reduction in the lamp is 1 watt. To get 3 to 6 watts per lamp +
ballast the rapid start ballast would have to have an internal power
loss of 2 to 5 watts per pair of lamp power windings, which is much
too high to be reasonable.

haven't looked at what it does to lamp life, but instant start is the worst
for that.

I don't know where you get your data by the life of preheat lamps is
far worse than instant start lamps. That is one reason why preheat had
virtually disappeared from the US market in favor of rapid start and
instant start. Preheat remains popular only for lamps that can be run
directly from the power line with a simple series inductor or
resistor. For 120-volt circuits this limits lamps to 2 feet long for
T12 diameter. In those location of the world where the line voltage is
220 to 240 volts, preheat and a series inductor is used with 4-foot
lamps.

It gets confusing too that most commercial or industrial types are
specified at 10 hours per start, while residential lamps are rated for 3
hours per start.

Fluorescent lamps are rated on a 3 hour on, 20 minute off cycle. This
includes what might be called commercial and residential types, though
there is no formal distinction between the two. You may be confused by
the fact that HID lamps are rated at 10 hours per start.

Lifespan drops dramatically with more frequent starting
cycles.

Most dramatically for preheat and instant start lamps. Less
dramatically for rapid start. And for well designed programmed rapid
start systems there can be virtually no loss of life. Osram sells a
programmed rapid start CFL in Europe that is rated for 500,000 starts.

--
Vic Roberts
http://www.RobertsResearchInc.com
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