light fiture and common neutral

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blackknight6945

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I have several contractor CFL light fixtures where I work at that have four circuits per fixture and a common neutral to all four. I'm going throught electronic ballasts and lamps like crazy. Question: Is voltage back feed off the tied neutral causing this? Even if some of the circuits are off, can the ballast still be damamged thru the neutral???
 
blackknight6945 said:
I have several contractor CFL light fixtures where I work at that have four circuits per fixture and a common neutral to all four. I'm going throught electronic ballasts and lamps like crazy. Question: Is voltage back feed off the tied neutral causing this? Even if some of the circuits are off, can the ballast still be damamged thru the neutral???
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Please explain the bolded part more thoroughly. Different circuits or different switch legs on the same phase?
 
blackknight6945 said:
I have several contractor CFL light fixtures where I work at that have four circuits per fixture and a common neutral to all four.
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Four branch circuits or one circuit with four switches?

Question: Is voltage back feed off the tied neutral causing this? Even if some of the circuits are off, can the ballast still be damamged thru the neutral???
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No
 
4 light fixture circuits with one neutral

4 light fixture circuits with one neutral

i'm confused as to how you can have 4 circuits with the same neutral?
 
Let me explain this like a Master Card commercial.

A CFL light fixture contains four Advance, four pin base, electronic rapid start ballasts per fixture; TWO CFL's per ballast


EACH ballast is on its own seperate branch circuit ( each has its own circuit breaker)

ALL the ballasts share the SAME common neutral within the light fixture.

Referring back to my original thread and getting an explaination to my problem-Priceless
 
If all the fixtures in the wharehouse is wired to the same neutral + 4 circuits then I can see a very bad loss of balance from resistance loss in the neutral. this would lead to sending higher voltage to some of the ballast, but to share a neutral between 4 circuits the neutral would need to be sized to the sum of the circuits shareing the same phase. keep in mind that with CFL's that they are using electronic balast, and in a 3 phase Y system the harmonics could add to the neutral loss.


Yeh I know I havent made a post in a long while so I figured I'd break the ice.
 
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I'm still confused. If you have several of these lights wired this way, then what you are saying is every ballast in every light has it's own circuit? And that I assume would mean either you have a ton of switches or you operate them with the breaker?
 
This is not uncommon, as in some warehouse installs this is done to have the ability to turn off some of the ballast in each fixture to lower the light levels when not as bright of lighting is needed, but keeping an even light level through out the warehouse.

also it is common to use (SW) rated breakers as switch's in commercial and industrial applications:)
 
hurk27 said:
This is not uncommon, as in some warehouse installs this is done to have the ability to turn off some of the ballast in each fixture to lower the light levels when not as bright of lighting is needed, but keeping an even light level through out the warehouse.

also it is common to use (SW) rated breakers as switch's in commercial and industrial applications:)
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Sorry, but I've never seen every single ballast in a whole wharehouse running on their own circuit. Sure would fill up a panel fast. Especially if you have four ballasts per fixture. With a 42 circuit panel that is on 10 light fixtures. I have seen where they install them so the switches or breakers (swd of course) run half of the lights, but not each and every ballast.
 
Got it now. Each light has four sepearte circuits and not that each light has four dedicated circuits. My bad. Yea, you need to run some more wire sounds like.
 
Thank you, blackknight. After reading some of the possible solutions, I ran extra neutrals to the fixtures in hope of resolving my problem. If the this fixes it, I have several other buildings that will require the same thing.
 
daleuger said:
I'm still stuck on the 4 circuits on 1 neutral too....:-?
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What if they said multiple switch-legs sharing a neutral? The legs could even originate on the same circuit, like split-wired receptacles.

Imagine running a single 3-conductor cable from light to light, tying the ballsts for the inner pair of tubes to one leg, and the ballasts for the outer pair on the other leg. The single neutral would be common to all ballasts.
 
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