Hi..Typical 2' 2 lamp flourescent fixture.I got called to a residence for a bad fixture. I replaced the fixture and still lamps still glow dim. I ran through the typical....lamps fine... voltage fine... polarity fine...The one problem I did see was the old cloth romex.(No Ground).As far as I know the ground sould not have any effect on the the fixture.I could be wrong...maybe the ballast needs the ground??? Any ideas.....????

Hi ToHo,
I'm not sure of the theory as to why, but yes, just the other day I had a service call for a flourescent fixture that was "flickering and taking a long time to come on". I changed the bulb, same problem. Started to change the fixture but noticed the ground was loose. I scraped the paint under the ground screw and torqued the screw down tight on the ground wire and the problem went away. Again, I'm not sure of the theory behind this. Perhaps one of the many very sharp folks on this forum can educate us on that

We have been through this many times here. My position has always been that it is a misconception that fixtures require a ground to start and operate regardless of what you may have observed. Apparently there is another reason for the fixture failing to start that you missed.

-Hal

Hal

I disagree with you. I have personally witnessed fluorescent fixtures failing to start due to the lack of grounding. I also suggest you read the trouble shooting guides from the ballast manufactures with will tell to check for proper grounding if the lamps are having problems starting.

Curt

Curt... I'm not sure How the ground affects the ballast??? I agree with what your saying..I'm curious to the theory behind it.. ToHo

i would assume that this required ground would be in cahootz with the magnetic field.

in the one bank we were in a previous contractor put a 3 phase temporary subfeed cable right up against the one phone line we ran. it was rendered useless with static and intereference. all we had to do was put a metal plate between the phone and subfeed (acted as a ground cause it was touching a bonded conduit) and it cleared the static up instantly.

long story short maybe the reasom it's required to be grounded, is due magnetic interefernce within the fixture.

How come some fluorescent desk lamps that use transformer-based ballasts don't have ground connections? All the ones I've seen used have two-pin plugs. Unless it's after a certain size, wattage, that grounding becomes important?

where are the ballasts located in relation to the bulb? and what is teh ballast size on those desk lamps? if it's a small ballast located in the base, maybe the magnetic field isn't enough to effect teh bulb. i'm just throwing guesses out this is an interesting topic!

As long as we are speculating, I'll throw in.

I remember working a job a few years ago and getting a tingling leaning up against a drop ceiling grid. The grid was isolated from the other grid by the four drywall walls of the office. The 2X4 lay-in wasn't grounded and my meter showed slight voltage to ground (I think I used a sprinkler pipe). shut the light off, no trickle. Ground the light, problem solved.

Also my parents have fluorescents that intermittently start in hot, humid weather. They are ungrounded, and after having my memory jogged by this post, I need to fix that. It will probably stop the sluggish start (I've already replaced the ballasts).

As to the ungrounded desk lamps, are those twin tube? maybe the field cancels itself out as it doubles back, (similar to the requirement in having both conductors present in the 300-3(b) requirement.)

I don't believe the equipment ground has anything to do with ballast function. I do, however believe the ballast must be solidly grounded or bonded to the fixture for proper operation.
jps, try removing the lamps from your folks fixtures and cleaning them. I read that dirt on the lamps combined with humid weather will cause starting problems.

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.

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).]

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.

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).]

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?????

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!!

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).]

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.