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.
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.
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!
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.