# Exploded T8 tubes



## Vintage Sounds (Oct 23, 2009)

Were these magnetic ballasts? A 120-277 electronic ballast probably would have kept operating like normal.


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## amigi968 (May 24, 2008)

I'm surprised the ballasts are ok.


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## Spark Master (Jul 3, 2012)

Out of curiosity, I went back to the job site. They are 120volt ballast !!

And I found out, once the neutral was cut, the lamps remained lit. (with the exception of the burnt out tubes) At least 1 tube in every 2x4 layin burnt out.

But get this. The fixtures remained lit, until they flipped the light switch off-on. Then the fixtures would not re-light with the cut neutral, even though there were 2 hot legs, with the floating neutral.


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## Electric_Light (Apr 6, 2010)

Magnetic or electronic?


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## Spark Master (Jul 3, 2012)

T8 Electronic ballast.


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## jordandunlop (Feb 28, 2009)

What were you guys doing changing out ballasts?


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## Spark Master (Jul 3, 2012)

They were cutting in a new fixture, earlier on in the run. So in between the breaker, and the existing fixtures.


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## Black Dog (Oct 16, 2011)

Spark Master said:


> They were cutting in a new fixture, earlier on in the run. So in between the breaker, and the existing fixtures.


It is possible that the fixtures ahead had a number of lamps that were already burnt out--Many of the T-8 Lamps ends shatter when they burnout.


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## Spark Master (Jul 3, 2012)

No, 3 people saw the change immediately when the neutral was cut. And the maintenance man has every bulb lit in this building. 1st class property management.


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## Electric_Light (Apr 6, 2010)

I didn't know they still made 120v ballasts for commercial use. They're mostly 120-277v since they make fixtures cheapers by combining two SKUs and they're more efficient in the real world, because, if you give them anything in between 100-300v, they draw the same wattage. Line voltage variation significantly affected performance and power consumption on older ballasts.

Electronic ballasts appear to behave like a heating element, but they're not. Look at the diagram. if you switch off one of the leg, that one is taken out of circuit. If you then remove the neutral and the other two loads are well balanced, they'll operate in series each getting 104v and form a circuit like the bottom half of the picture. 

If you switch it off, they're not going to stay in balance during starting, so one will get an excess voltage. Perhaps the MOVs in the ballast divert the surge voltage and throw the lamps under the bus as a surge arrester to protect itself. This would explain why the lamps got cooked.


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