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Fluorescent Starters


I think starters are based on the lamps arc voltage, Basically lamp length, longer lamps have higher arc voltage.

I am somewhat familiar with fluorescent lamps. For instance a 4' 40w T12. When power is applied the but before the lamp is lit (open circuit) the voltage is around 200 volts. This is not enough to strike an arc across a cold lamp, but the starter does conduct. The starter will heat up closing the contacts inside of it. Now it sends power to the filaments, heating the lamp. The starter will conduct until the contacts open after a second or so. When the contacts open it creates a high voltage spike which either lights the lamp or the process repeats. Once the lamp lights it's arc voltage is around 100 volts which is not high enough for the starter to conduct so it is effectively out of the circuit.

The ballast is there to limit current and it helps provide the high voltage spike when the starter opens. Fluorescent lamps are negative resistance, meaning as they heat up resistance goes down, so they need a ballast to limit lamp current otherwise the lamp would burn up quickly once it was lit.

This pertains only to PREHEAT fixtures. rapid start systems are not the same and I'm not as familiar with them.

Someone more knowledgeable than me could probably do a better job of explaining it, but thats as good as I can do.

PS. I don't think fluorescent lights are miserable at all. Good ones are very reliable and last for years, I've got a couple that have original ballasts that are dated from 1946 and 1947!


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I suppose there would be plenty of older design fixtures still using actual starters.

Most of the modern equipment I've put out uses programmed-start electronic ballasts with T8 or T5HO lamps. All of the T12 equipment at my workplace has been retired, and I've been advising homeowners to plan on phasing out T12 equipment in favor of T8 or LED.

While these electronic ballasts are not a fan of noisy power lines, they seem to have no trouble at all bringing cold lamps up to full power in a hurry.

The traditional T12 with a starter though, was a 3 part system. You had your bulbs, your ballast, and your starter.

It was wired so that all of the filaments were in series, while the bulbs themselves would be in parallel once the tubes ignited.

Initially current would flow only through the filaments, getting them hot. Then the starter would open the circuit, and the sudden loss of current would make the ballast produce a high voltage kick to ignite the tubes.

Once the tubes were ignited, current would much rather go through the low resistant path they offered than through the filaments and starter. So the starting circuit would sit doing next to nothing, while the ballast regulated the current through the tubes.

I've never gotten to work on a starter-based fixture operating on anything other than 120v, but all of the electronic ballasts that I have put in service are capable of operating on anything from 120-277vac without issue. Don't have to change taps or anything, just wire it up and let the electronics do their thing.


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I do know from experience that the electronic ballasts do not like 480 volts. :O

It was my first job, and being a brand new apprentice I was tasked with dropping 1,000 2x4 fixtures into place in a new Target strore. :crazy: They gave me a huge scissor lift, and I could fit 54 of these fixtures at once on it, then drive off to where they needed to go. Actually a lot of fun for a new guy. :D

Afterwards another apprentice and I went back and screwed them to the T-bar ceiling, applied the earthquake wires, and connected them.

When we were all done and threw all of the switches, 7 of them did not light. 5 of them were simply bad, but two of them popped when they got 480 instead of 277.

They had two circuits in each cable, and the fixtures were to alternate between the two down the row. But, up there in the dark, it was not inconceivable to interpose a white and a yellow. Twice out of 1,000, evidently. :brows:


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I like fluorescents fine, but I've been replacing my T8 bulbs with LED tubes when they (or the ballast) burn out. The LEDs make really nice, bright white light. In some cases, I use only one tube where the fixture had two and it is still plenty bright. More light, less watts, and supposed to last almost forever. We'll see about the last part, but I am very happy with the light. And no noise.