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Joined: Jan 2004
Posts: 171
M
Member
Same here. I have some flourescent lights above a kitchen counter in an older home. They are not grounded and sometimes don't come on. All I have to do is simply touch them and they light up. I suppose someday I should ground them.

Joined: Jan 2003
Posts: 1,429
L
LK Offline
Member
Rapid Start Fixtures need a ground to start properly.

They may start without a ground if the current is just beginning to lag, "do you feel lucky today" type of start.

For a good insite on understanding these problems go to http://www.advancetransformer.com/literature/pdf/FLB_Pocket_Guide.pdf

[This message has been edited by LK (edited 12-31-2004).]

Joined: Apr 2001
Posts: 518
J
Member
Ever wonder how lamps stay "warmed up" for instant-on when the circuit is "off?"

I have had some problems with certain motion sensors, fhoto cells, and timers as well. The one thing these all had in common were electronic components.

My own pet theory is that these electronics use the ground path as a "neutral" and operate off the tiny voltage differences between the real neutral and the ground. I can't see how else they operate when the "hot" is turned off.

Joined: Dec 2003
Posts: 886
H
Member
According to the Advance Ballast Pocket Guide:

The Rapid Start lamp operates on the principle of utilizing a starting voltage which is insufficient to start the lamps while the cathodes are cold but is sufficient to start the lamps when the cathodes are properly heated. This voltage range between starting cold and starting hot is a very narrow band of voltage which must be closely controlled by the ballast in order to prevent either failure of the lamps to start or instant starting of the lamps with cold cathodes which is detrimental to the lamps. In order to stay within this range of voltage, it is necessary to excite the gas within the lamps by means of an external voltage applied between the lamp and the reflector or channel (the starting aid).

In order to act effectively, the fixture must be connected to ground and the white lead of ballast connected to ground lead (neutral) of the power line.


Well, apparently they are relying on the neutral to ground bond at the service for this to happen because what they are saying is they need to have the white wire from the ballast to be connected to the the fixture sheet metal. Grounding the fixture would be the only legal way to accomplish this.

What would happen if the hot and neutral were reversed somewhere in the circuit? Another reason for the fixture not starting?

Going to be bull headed here and still stand on my old argument that a ground is not necessary- there are plenty of 2 lamp 48" rapid start fixtures available as "shop lights" and "grow lights" with 2 wire cords on them. Same ballasts, same lamps and they all start.

I know what you all are saying but I have never had a fixture fail to light because of a missing ground. It's always been because of other things even as weird as incompatible lamps from one manufacturer.

Ever wonder how lamps stay "warmed up" for instant-on when the circuit is "off?"

John, they don't. How could they? What they are talking about is when the fixture is turned off then turned back on while the lamps are still warm.

-Hal


[This message has been edited by hbiss (edited 12-31-2004).]

Joined: Dec 2003
Posts: 751
E
Member
Checking out the link from LK, I read the following:


The Rapid Start lamp operates on the principle of utilizing a starting voltage which is insufficient to start the lamps while the cathodes are cold but is sufficient to start the lamps when the cathodes are properly heated. This voltage range between starting cold and starting hot is a very narrow band of voltage which must be closely controlled by the ballast in order to prevent either failure of the lamps to start or instant starting of the lamps with cold cathodes which is detrimental to the lamps. In order to stay within this range of voltage, it is necessary to excite the gas within the lamps by means of an external voltage applied between the lamp and the reflector or channel (the starting aid).

In order to act effectively, the fixture must be connected to ground

and the white lead of ballast connected to ground lead (neutral) of the power line.

Thus it is stated on the label of Rapid Start ballasts "Mount lamps within ½ inch (3/4 inch or 1 inch) of grounded metal reflector."

Fluorescent fixtures are designed to provide the proper lamp-to-reflector distance.


So, I gather from this that your fluorescent luminaires may have been engineered to not always work unless there is a grounded strip or reflector nearby (1/2 to 1 inch).

It does matter if some luminaires are grounded, and doesn't matter for others that are not engineered to such tight voltages. Who woulda thunk it?????


Earl
Joined: Dec 2004
Posts: 46
T
ToHo Offline OP
Member
earlydean
I think you nailed it..... I want to thank everyone for their input.. I'm new to the forum... My wife thinks I'm nuts because I have been checking the forum for info constantly....15yrs in the business and sometimes you come across things that make you feel like its your first day!!!! Thanks again to everyone!!

Joined: Dec 2003
Posts: 886
H
Member
It does matter if some luminaires are grounded, and doesn't matter for others that are not engineered to such tight voltages. Who woulda thunk it?????

Yeah, I think that's the gist of it. This is actually the first time that I have seen a ballast manufacturer expand on this grounding requirement. In the past all they said was "Mount lamps within ½ inch (3/4 inch or 1 inch) of grounded metal reflector".

If you look at the circuitry they show inside a magnetic rapid start ballast there is nothing there that would maintain the tight voltage tolerances they talk about. On top of that ballasts are supposed to be able to operate with a range of lamps, usually standard wattage and energy saving from any manufacturer. That kind of throws a monkey wrench into the tight tolerance stuff.

My take, and my own experience, is that whether these things operate or not is a crap shoot. I've had fixtures where I replaced everything except the sheet metal and they still wouldn't start. I don't think you can point a finger at any one reason other than poor ballast design (probably driven by cost) which fails to account for the multitude of different lamps and manufacturing standards.

I say ground them because they should be grounded per the NEC for safety reasons but don't count on that as a reason for them not starting.

-Hal



[This message has been edited by hbiss (edited 01-01-2005).]

Joined: Dec 2004
Posts: 161
G
Member
Same technique as Xenon flash tubes! Pin at each end with ~300V dc across, then put a hv pulse on a bit of wire wound around the glass tube near one end. High voltage pulse rips ions off pin inside tube creating plasma which then arcs to other end.

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