T8 bulbs working on T12 ballast

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GG

Senior Member
Location
Ft.Worth, T.X.
I went to a job today and on all their F40T12 fixtures where 1 or 2 of the 4 bulbs had burned out they had replaced them with T8 bulbs and they were all working. Why would a T8 bulb work on a F40T12 ballast, and will the T8 bulbs burn out faster? I just always assumed T8 bulbs would not work on a T12 ballast, but aparently they do.
 
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fireryan

Senior Member
Location
Minnesota
If you run a t8 bulb on a t12 ballast you will have premature bulb life as the t12 ballast will over "tax" the bulb. If you run it vice versa and have a t8 ballast running a t12 bulb you will have premature ballast life as the t12 bulb takes more to run and will over work the ballast.
 
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GG

Senior Member
Location
Ft.Worth, T.X.
fireryan said:
If you run a t8 bulb on a t12 ballast you will have premature bulb life as the t12 ballast will over "tax" the bulb. If you run it vice versa and have a t8 ballast running a t12 bulb you will have premature ballast life as the t12 bulb takes more to run and will over work the ballast.
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Thank you for the info. Do you happen to have any link to a site I could print some manufaturers data stating what you just told me. i wanted to show these customers something "official" looking. They seem to think since they are working like they are that there is no problem.
 
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Strife

Senior Member
Ok. Let's keep in mind one thing. Unlike incandescent lamps where the filament is the load, the fluorescents and HID lamps are actually a conductor, where the gas gets ignited by the amperage created by the load we call ballast. Both the T12 and T8 use same kinda gases, but the t12 need higher amperage to be pushed thru (and voltage) to ignite the gas. So a T8 should definitely work on a t12 ballast(as the t12 use higher voltage and amperage to ignite the gas). Would they have a premature life? Hard to say, if the gas stays intact and doesn't leak, no. Remember, the lamps is a conductor here, so look at it as a piece of #12 wire.

GG said:
I went to a job today and on all their F40T12 fixtures where 1 or 2 of the 4 bulbs had burned out they had replaced them with T8 bulbs and they were all working. Why would a T8 bulb work on a F40T12 ballast, and will the T8 bulbs burn out faster? I just always assumed T8 bulbs would not work on a T12 ballast, but aparently they do.
Click to expand...
 
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BullsnPyrs

Senior Member
Location
Saint Joe, Arkansas
Strife said:
Ok. Let's keep in mind one thing. Unlike incandescent lamps where the filament is the load, the fluorescents and HID lamps are actually a conductor, where the gas gets ignited by the amperage created by the load we call ballast. Both the T12 and T8 use same kinda gases, but the t12 need higher amperage to be pushed thru (and voltage) to ignite the gas. So a T8 should definitely work on a t12 ballast(as the t12 use higher voltage and amperage to ignite the gas). Would they have a premature life? Hard to say, if the gas stays intact and doesn't leak, no. Remember, the lamps is a conductor here, so look at it as a piece of #12 wire.
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Not quite accurate. The lamps and ballast are a system designed to work with thier complimentary parts. T8 lamp life does decrease when run on a T12 ballast. We used to catch retrofit cheaters by looking for the premature blackening on the ends of the T8 lamps.
 
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jmellc

Senior Member
Location
Durham, NC
Occupation
Facility Maintenance Tech. Licensed Electrician
BullsnPyrs said:
Not quite accurate. The lamps and ballast are a system designed to work with thier complimentary parts. T8 lamp life does decrease when run on a T12 ballast. We used to catch retrofit cheaters by looking for the premature blackening on the ends of the T8 lamps.
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Speaking of such, how many of you have done retrofits? Do the kits work well and fit a wide range of fixtures? I'm sure I'll get a call for one sometime soon.
 
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