# output voltage on a T8 ballast



## sparkn890

I'm in class right now and a few people are saying that a T8 ballast will have an output voltage of 3-5Kv.... no way... I noted to the people that said that to take a look at the ballast wires and tell me the insulation rating...600v like I knew it would be. Someone please back me up and tell me output is between 300-600 volts


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## BBQ

sparkn890 said:


> I'm in class right now and a few people are saying that a T8 ballast will have an output voltage of 3-5Kv.... no way... I noted to the people that said that to take a look at the ballast wires and tell me the insulation rating...600v like I knew it would be. Someone please back me up and tell me output is between 300-600 volts


A very hard number to pin down as the job of the ballast is to adjust the voltage to keep the current constant.

Because of this often the numbers given will be the open circuit voltages and they greatly depend on the type and size of lamp. 

In this link http://code-elec.com/content/00/01/53/48/38/userimages/fluorescent ballast troubleshooting guide.pdf you can find what are considered the minimum open circuit voltages the top end being about 600 volts.

However these are minimum voltages to get the lamp to strike, the actual values would likely be higher.

Once the lamp strikes the voltage will drop.


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## BBQ

By the way, 'pulse start' metal halide fixture will put out well over 1KV.


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## swimmer

sparkn890 said:


> I'm in class right now and a few people are saying that a T8 ballast will have an output voltage of 3-5Kv.... no way... I noted to the people that said that to take a look at the ballast wires and tell me the insulation rating...600v like I knew it would be. Someone please back me up and tell me output is between 300-600 volts



I tried measuring voltages on a working T8 electronic ballast once, while the light was on. The only measurement that made sense was the 120V power input.


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## Shockdoc

This is one for BBQ, another myth taught to me in my helper days.....It is non compliant to install an 8' or HO flourescent fixture in a residence due to operating voltage at pins, T or F ?


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