Do Fluorescent Fixtures Really Need a Ground?

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Old 11-28-11, 11:49 AM
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Do Fluorescent Fixtures Really Need a Ground?

It is pretty much canon here that if a fluorescent fixture has trouble starting it may be a faulty ground but if you look closely that seems to be questionable logic.

Ground is not for function. It is for safety. It seems odd a device would need something not intended for function. It seems odd that fluorescent fixtures existed and worked long before grounding was common. It seems odd that CFLs seem to work fine in ungrounded fixtures. It seems odd that fluorescent table lamps usually don't have a grounded plug.
 

Last edited by ray2047; 11-28-11 at 02:03 PM.
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Old 11-28-11, 12:33 PM
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Canon, Ray, only one n. http://www.merriam-webster.com/dictionary/canon

Only rapid start and maybe instant start florescent lamps need a grounded reflector, the old preheat models that had starters worked just fine without grounding. I don't know exactly how or why but the grounded reflector has something to do with ionizing the gas inside the tubes. Sometimes just running your hand on or near the tube will cause the lamp to work.
 
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Old 11-28-11, 12:35 PM
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No, a ground is not needed. Heck, in some cases a fixture is not even needed. Back when LORAN was still used for navigation all you had to do was hold a fluorescent bulb in the air near the tower and it would light.

As for the ground and it's usefulness the neutral and ground wires tied together in the breaker box. Two wires going to the same place??? Yea, you can argue that if something goes wrong the ground wire safely carries off the current but can't the neutral wire do that? I think somebody writing the codes has stock in a ground wire company or owns copper futures.
 
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Old 11-28-11, 02:04 PM
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Color me red faced. Corrected.
 
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Old 11-28-11, 03:55 PM
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I don't know. It could have something to do with completing the electromagnetic field that excites the fluoron. You know sometimes with a no start, you rub your hand on the bulb and it starts. Maybe the fixture casing needs the ground to be "part" of the action.
 
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Old 11-28-11, 06:06 PM
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Originally Posted by Pilot Dane View Post
No, a ground is not needed. Heck, in some cases a fixture is not even needed. Back when LORAN was still used for navigation all you had to do was hold a fluorescent bulb in the air near the tower and it would light.

As for the ground and it's usefulness the neutral and ground wires tied together in the breaker box. Two wires going to the same place??? Yea, you can argue that if something goes wrong the ground wire safely carries off the current but can't the neutral wire do that? I think somebody writing the codes has stock in a ground wire company or owns copper futures.
The neutral is not connected to the metallic enclosure of a fixture so if a short existed the fixture would remain hot and a shock hazard so a grounding means is needed.

A grounding means is needed for fluorescent fixtures because an item is required to be installed according to the instructions. Metallic portions of the housing are also required to be grounded. As Ray pointed out the lack of a ground may affect the operation of the fixture, although I do not know why.
 
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Old 11-28-11, 07:01 PM
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Sometimes just running your hand on or near the tube will cause the lamp to work.
And in the case of outside high output fixtures, sometimes cleaning the lamps will cause them to work.
 
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Old 11-28-11, 07:28 PM
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I can't prove it but it is my belief the failure to start unless grounded is perhaps due to a weak ballast. That the ground isn't need if the ballast is functioning correctly. The ground might help but is compensating for a ballast not putting out enough power. I just find it hard to believe that they would build it to need something that may or may not be present. That would seem to be a design failure to me.

I have an ungrounded fluorescent table lamp. It starts every time and no it doesn't have a starter. Seems to prove my theory to me.

I wonder how many people we have told to improve the ground to their fluorescent fixture actually saw an improvement in starting? I wonder if changing the ballast would have accomplished the same thing without improving the grounding?
 
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Old 11-28-11, 08:02 PM
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Going back about three decades, my in-laws had a circular florescent fixture in their bathroom that was cantankerous. Sometimes it would start right away and other times it would take several minutes. The house had knob & tube wiring so working from the attic I just ran a green conductor from the lamp housing to a nearby water pipe. Not a code-approved method but it made the fixture light immediately every time.

In my parent's house we had a basement shop. There were two 2-tube, F30T8 fixtures. At first these were wired without any ground and they worked okay, one of them would sometimes take a few seconds to light. Eventually neither would light for several minutes and I added a real equipment ground. This helped for a while but eventually it got to the point that even leaving the switch on for several minutes often would not get the fixtures to light. Bulbs were changed with no effect.
 
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Old 11-28-11, 08:18 PM
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Aww gee, Furd, Your first example disproved my theory and your second seemed to prove it.
 
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Old 11-28-11, 08:29 PM
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In the second example if it makes you feel any better, the fixtures were really old. I think my daddy swiped them from the dumpster at some job he worked.
 
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Old 11-29-11, 10:30 AM
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Originally Posted by Pilot Dane View Post
As for the ground and it's usefulness the neutral and ground wires tied together in the breaker box. Two wires going to the same place??? Yea, you can argue that if something goes wrong the ground wire safely carries off the current but can't the neutral wire do that? I think somebody writing the codes has stock in a ground wire company or owns copper futures.
Pilot, it appears that you have no idea of what the equipment grounding conductor does. I assure you, it does NOT "safely carries off the current" but instead it allows a high current to flow briefly in order to shut down the circuit overcurrent protector, the fuse or circuit breaker.
 
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Old 11-29-11, 05:40 PM
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Rapid start lamps require an electric field to start properly. The ground conductor helps that field be setup. Check out this link: Rapid Start Fluorescent Fixtures
 
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Old 11-29-11, 05:56 PM
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Thanks for the link. I see they show the ground to the reflector as part of the starting circuit. The ground draws radiated current causing the electron flow to increase. That I think answers my question.
 
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