# Emergency Ballast



## gnuuser (Jan 13, 2013)

its possible some ive had to change at work used 4 foot lamps and only one side would light while the other remained dark.
changing the emergency ballast corrected it.

you could probably find more info on it from the manufacturer of the fixture


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## Monkeyboy (Jul 28, 2012)

Be ready for the insane cost of emergency ballasts; approx. $150


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## A Little Short (Nov 11, 2010)

gnuuser said:


> its possible some ive had to change at work used 4 foot lamps and only one side would light while the other remained dark.
> changing the emergency ballast corrected it.
> 
> you could probably find more info on it from the manufacturer of the fixture


I couldn't find anything on the ballast or fixture. The E ballast looked like it was wrapped in aluminum foil.
But I looked up wiring diagrams from several mfg. Most were the same.

With all that said, I got the light going without messing with the E ballast.
It was late when I got to that light yesterday and I had been on a ladder for 8 hours so I was too tired to mess with it then.
But I got to thinking I didn't see the LED lit on the test button. So the first thing I did this morning was check the voltage/wiring. I had used my tic tester before and it lit but I didn't know for sure about the voltage. When I started to remove the wire nut from the neutral so I could put my meter lead on it I saw the light flicker.
Turns out the neutral was loose. The regular ballast probably wasn't even bad. But I was hired to change ballast so that's what I did!


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## Electric_Light (Apr 6, 2010)

And here lieth y you pre-twist the wires before putting on wire nuts. It's easy for one to slip away unnoticed.

Just on a related note, programmed start ballasts are expensive and modern ones have a computer chip built into it and can tip off a bad ballast even if it isn't.

T8 lamps actually have a filament on each end like a T12. Programmed start ballasts pre-heat them first, then apply starting voltage. If the wires are loose in one of the sockets, a bent knife edge, misaligned lamp or a broken filament is present, the software code will deny starting. If lamps are going bad and they fail to strike, the ballast will lock out and can require a power down of 15 seconds or so. This is so that it will not cause intolerable lamp flashing with continuous retry. Some will lock out after one try. Some will allow several tries. 

Lamps that's been kicked around too much may have a few lamps with a broken filament. They will light off in instant start, but lock out programmed start ballasts.

Some are self resetting if new lamps are installed hot. Some require a power cycle. If you're using energy saver 4 foot lamps in a cold area which aren't supposed to be used below 50F, you might never get the ballast out of lock out until you install the proper lamps. I've seen this happen after 25W 4' lamps in maintenance room meant for general area found their way into refrigerated area lighting. 

Always double check wiring and try a new set of lamps. If in doubt, ohm the filaments in each lamp. 

Some 3-4 lamp dimming ballasts with series wired lamps are especially complex and cost north of $100 a piece and special order, so triple check everything and test it on ground before ordering a replacement. 

They've got quite good at making them idiot proof. Some of them will resist most forms of misuse that would have destroyed older design like hooking up shunted sockets or 277v across 0-10v terminals, but a bad lamp will lock it out every time and make it seem like it's fried even if it isn't. 



gnuuser said:


> its possible some ive had to change at work used 4 foot lamps and only one side would light while the other remained dark.
> changing the emergency ballast *corrected *it.
> 
> you could probably find more info on it from the manufacturer of the fixture


Did you mean one end of the lamp or one side of the fixture? It's perfectly normal for emergency ballasts to only light one lamp depending on configuration. 

That's intentional, because it's not necessary to light both lamps in a two lamp fixture, but two single lamp fixtures spaced apart sufficiently far apart or around a corner would need both lamps lit.


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## gnuuser (Jan 13, 2013)

Electric_Light said:


> Did you mean one end of the lamp or one side of the fixture? It's perfectly normal for emergency ballasts to only light one lamp depending on configuration.
> 
> That's intentional, because it's not necessary to light both lamps in a two lamp fixture, but two single lamp fixtures spaced apart sufficiently far apart or around a corner would need both lamps lit.


8 foot fixture with 4 4 foot lamps (2 per end)
one end of the fixture would light but emergency ballast side wouldn't
(after a long power outage) on further testing the ballast was bad
on first installation of these fixtures all 4 lamps were lit up

the company was trying out these fixtures :laughing:
imho. they were not bad but my preference would have been independent emergency lighting system


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## Holop (Sep 8, 2008)

Always double check if regular ballast is not a dud. And most of the times if it doesn't fire then emergency ballast is bad.


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