Why does fluorescent require ground

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Here is another makers take on the subject.

Radionic Industries

Trigger Start:

Trigger start is a term used for ballasts which operate pre-heat start lamps in a rapid start manner. They supply higher filament voltages to heat the electrodes to start the pre-heat lamps, to simulate the rapid start system. A grounded reflector close to the lamp, together with a grounded line circuit, is required to provide a capacitive starting aid effect between lamps and fixture and assist ionization in the starting process.
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Rapid Start:

Rapid start ballasts provide the proper energy levels to heat the lamp filaments continuously, through small low voltage filament windings. The open circuit voltage of the ballast is adequate to start the lamp only after the filaments have been heated to emission temperature. A grounded reflector close to the lamp, together with a grounded line circuit, is required to provide a capacitive starting aid effect between lamps and fixture and assist ionization in the starting process.
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Q: What do I do if my fixture lights sometimes and not others? Or, what do I do if my fixture lights if I touch the bulb?

A: This may be a grounding problem either with the way the fixture is wired or if your house does not have properly grounded circuits. Rapid start and trigger start ballasts MUST be grounded (both the ballast and the fixture) and the lamp must be within ?" of grounded metal (fixture or reflector). We suggest you hire a licensed electrician for safe diagnosis and repair.
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Well that answers it them. :)

From what I can understand the lamp will still light if it's not in close proximity to a grounded surface, but will take longer to start.
 
peter d said:
Well that answers it them. :)

From what I can understand the lamp will still light if it's not in close proximity to a grounded surface, but will take longer to start.
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I agree, touching it will often force a start as well.
 
benaround said:
I wonder how many 100's of Electricians just learned why the fixture really

needs to be grounded, I know of one for sure.
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You can make that two, and thanks for the links Bob.

But as Larry pointed out, I also have questions about this statement.

In order to act effectively, the fixture must be connected
to ground and the white lead of the ballast connected
to ground lead of power supply.
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iwire said:
I understand this to mean it has to be supplied by a branch circuit containing a grounded conductor.
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Yes sir, we have wired them this way for decades.

white lead of the ballast connected
to ground lead of power supply
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I believe this was not what Advanced really wanted to say here.
 
080830-1513 EST

Larry:

I am not disagreeing with what you said the manufacturer has said about Instant Start lamps. It may be at least useful in improving lamp life and maybe operation over a wider temperature range. If the manufacturer requires you to do it, then do it. I suspect the reason relates to running the filaments at a lower temperature to improve efficiency, and thus greater starting problems without the external electric field to the sheet metal. If the reason for a requirement is given then a user can have an understanding of the process, otherwise it is guessing. I believe in the past with F40 bulbs and conventional ballasts that this grounding requirement of the sheet metal would not have been a requirement.

No direct information on need for an external electric field, but useful information:
http://www.ustr.net/electronics/fluorescent.shtml
http://www.light-link.com/resources/lightguides/ballasts.html

A fluorescent lamp contains an arc discharge during operation. This is essentially a constant voltage. Thus, it must be supplied by an approximation to a constant current source. That is one purpose of the ballast.

Interesting but sort of incomplete:
http://www.lightbulbs101.com/compact-fluorescent-light-bulbs.html
There are only 4 milligrams of mercury in a 40-watt compact fluorescent bulb. That?s about as much as the period at the end of this sentence. Coal plants release more mercury into the air than any other man-made structure. To light an incandescent bulb for 10,000 hours, a coal plant will release 10 milligrams of mercury into the air as opposed to only 2.2 milligrams for a CFL. CFLs actually produce 3.8 milligrams less mercury than incandescent bulbs. If you?re still concerned about mercury content, consider environmentally friendly cold cathode bulbs, such as Microbrite and Neolite CFLs. They contain only 1 milligram of mercury and are completely lead free.
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What size incandescent and CLFs were being compared? Are they referring to 40 W equivalent throughout the paragraph?


The following patent is quite interesting. It seems to be different.
http://www.wipo.int/pctdb/en/wo.jsp?IA=US1998014810&WO=1999005890&DISPLAY=DESC

This reference is not as useful.
http://nemesis.lonestar.org/reference/electricity/fluorescent/rapid.html

There is a lot to be learned by some searching. but it is not always correct. So it is necessary to ask basic questions and double check the results.



.
 
080830-2004 EST

My last post was meant to be addressed to Bob.

Chris:

Based on a CPL I disassembled recently the tube has a filament at each end. Whether you want to call it a Rapid Start or not is probably a function of the filament excitation and how it is controlled.

I believe it was with a standard CLF (in contrast with a dimmable) that I adjusted input voltage with a Variac (actually a Powerstat) and got reasonably good dimming for a CLF and near dropout I could see the filament glowing. Wihich type of lamp or which type of dimmer is foggy at this time relative to the filament glow.

One point that is now clear is that the dimmable CLF when supplied with a varying amplitude sine wave had almost constant light intensity down to about 95 to 100 V, then just quit. With a phase shift control dimmer it had a poor and limited dimming range.

The standard CFL with a Variac was much better but still did not have a good dimming range. I believe it cutout about 65 V. The standard CLF did not have a constant intensity characteristic with the Varic input.

.
 
gar said:
080830-0858 EST

I have rerun the Tektronix LC meter capacitance check and now read 14 pfd instead of 21 pfd. I might have misread the meter or improperly held it. Note capacitance in this range is very small. Holding a plastic screwdriver handle in my hand and touching the LC meter probe to the screw driver shank causes a reading of 8 pfd.

More experimenting indicates the problem was how I held the GFCI.

.
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like this ...
 
chris kennedy said:
Yes sir, we have wired them this way for decades.


I believe this was not what Advanced really wanted to say here.
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I think it is, they don't want you to connect the supply (black) to the white

of their ballast. Anyone can change a ballast, right?
 
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