Flourescent Lighting Fixture Starters

[Nardie]

Just recently I had an E&I mechanic experience an electrical shock while reinstalling a fluorescent lighting fixture starter. The starter is a FS-4 30-40W. The mechanic was replacing the bulbs for the fixture, and noticed the starter seemed not to be installed correctly since the fixture did not illuminate once the bulbs were replaced. So the mechanic removed it, inspected the starter, and reinstalled it after noticing no damage. When he twisted the starter into place he felt an electrical shock, and described the sensation as "it lit me up". He was standing on a fiberglass ladder, and stated "that only his right hand touched the starter". When a voltage test was performed with a low voltage proximity tester on the starter and fixture, the tester did light up only in proximity of the starter not the fixture. When the starter was tested with a Tegam 110 voltage tester, the voltage measured was 5V to ground. There was several different grounds used to include the light fixture. The starter was removed and damage was noticed. During a continuity test between the starter's male terminals to its casing, one male terminal was shorted to the starter's casing. The starter was replaced, and the light fixture began operating. So my question is this since I'm not very familiar with fluorescent lighting starters, what is the voltage conducted through the starter? Is it the normal line voltage of 120V, or does it operate at a lower voltage? I am trying to understand why when tested, the voltage on the starter's casing was measured only at 5V, yet the mechanic stated he felt the shock enter his right side and exited his left while standing on a fiberglass ladder, i.e. note he also stated his left hand was touching nothing, not grounded. Is it due to the current of through the starter, or something else? Any help would be greatly appreciated. Also, the mechanic is fine and was released by medical personnel with no restrictions. Thanks

 

[drcampbell]

An old-fashioned fluorescent fixture with a magnetic ballast and a mechanical starter connects one side of the starter to the hot wire.
The ballast and filament will limit current, but limit it to a much higher level (~1 amp) than is hazardous to a person. (~0.02 amps)

 

[hbiss]

... the mechanic stated he felt the shock enter his right side and exited his left while standing on a fiberglass ladder, i.e. note he also stated his left hand was touching nothing, not grounded.

Sounds like he was repeating the oft told story of someone who was actually shocked. Fear of electricity can make people believe things that didn't happen. Or maybe he is looking for a comp claim or lawsuit and wanted to cover his a** if something should happen later.

I could believe that he might have felt something in his hand when he removed and replaced the starter probably since some part of his hand or fingers also contacted the grounded fixture.

-Hal

 

[Nardie]

I appreciate the replies, however I would still like to know what voltage level the starter operates at? I do think the mechanic felt something, just not what was described. I am unfamiliar with starters in light fixtures, so would the ~1 amp at 5 volts give the mechanic the false sense of an electrical shock, or something else? When we tested the starter for voltage, I'm sure we had a good ground, however we tested with several different grounds, i.e. receptacle, unistrut, light fixture and conduit, and the meter stabilized at 5 volts. I'm a little puzzled so any assistance would be helpful.

 

[hbiss]

You say yourself you measured 5 volts so you have to believe that. It's limited by the ballast of which there are many different designs. So you can't say that, under the same conditions they all will cause the same voltage to be present on the starter to ground.

But don't go by what I say. Take the fixture, remove the starter and measure the voltage to ground from each of the two starter contacts in the socket. Remember too that the starter can be inserted either of two ways (there is no polarity) and you say that the starter had one side shorted to the case. So you have to think about whether the starter was removed and re-inserted before you took your voltage readings.

So you can answer your own question by assuming that the shorted side of the starter was connected to the highest of whatever you measure at the socket.

Now whether it caused the shock that was reported is another matter.

-Hal

 

[LarryFine]

I appreciate the replies, however I would still like to know what voltage level the starter operates at?

A starter is closed at first, so each filament sees 60v. After the lamp fires,the starter is open, so it has 120v across it. The ballast is a simple 1-coil inductor. See the diagram in post #2.

 

[kwired]

I appreciate the replies, however I would still like to know what voltage level the starter operates at? I do think the mechanic felt something, just not what was described. I am unfamiliar with starters in light fixtures, so would the ~1 amp at 5 volts give the mechanic the false sense of an electrical shock, or something else? When we tested the starter for voltage, I'm sure we had a good ground, however we tested with several different grounds, i.e. receptacle, unistrut, light fixture and conduit, and the meter stabilized at 5 volts. I'm a little puzzled so any assistance would be helpful.

What voltage you will measure will depend on whether you are taking measurement during pre ignition of the arc in the lamp, or after ignition, and also depend on working condition of the lamp and the starter.

With a lamp that hasn't ignited an arc yet and a removed starter - you will have one side of the starter socket at the same potential as the ungrounded conductor and the other side at same potential as the grounded conductor. Plug a properly working starter into the socket and have intact elements at each end of the lamp and you have a series circuit consisting of L1- ballast coil - end element of the lamp - starter - other end element of the lamp - N. There will be voltage drop across each segment of the circuit, but then the lamp is parallel to the starter once it has established an arc - but normally operating starter should be open when the lamp is lit - so it will have same potential across it as the lamp has from one end to the other when lamp is lit one end is directly connected to the grounded conductor - if wired like the drawing in post 2. If someone has input polarity wrong then that end is connected to the incoming grounded conductor - the whole thing still works because it is still 120 VAC across all of it either way.

 

[drcampbell]

Before the lamp turns on, the starter is closed and both sides will see "half" of line voltage.
After the lamp turns on, the starter is open. One side of the starter is "connected" to the grounded wire and sees "zero" voltage; (aka. "white", aka. "neutral") the other side is "connected" to the hot wire and sees "line" voltage.
(I've used quote marks because there are a few voltage drops here & there and what I said is not literally & precisely true)

When inserting the starter, there will be a moment when only one pin is in contact with the socket.
With one terminal of the starter faulted to its casing, its casing might have been energized with line voltage, or half of line voltage, either of which is hazardous.

The 5 volts you measured is almost certainly the result of voltage drop in the neutral wire. This is entirely normal.
(there's a little bit of voltage drop in the white wire because current's flowing, and no voltage drop in the green wire because no current's flowing)
Were you to remove the starter, turn it 180° and re-insert it, you'd probably see almost line voltage on its casing instead of almost zero volts.
(I am speaking hypothetically. Do not actually try it.)

It's not unusual to get a small shock while standing on a fiberglass ladder. Fiberglass is an insulator, but it's not a perfect insulator, and a little bit of dirt, moisture or capacitance will allow a little bit of current to flow.

If this is in a commercial/institutional/industrial building, it's possible that the fluorescent lamps are powered with 277 volts.

I recommend destroying this starter before disposing of it, to make it impossible for somebody else to repeat this episode.

 

[LarryFine]

I recommend destroying this starter before disposing of it, to make it impossible for somebody else to repeat this episode.

Or open it and see what caused the connection between internal wiring and the case.

 

[kwired]

Before the lamp turns on, the starter is closed and both sides will see "half" of line voltage.
After the lamp turns on, the starter is open. One side of the starter is "connected" to the grounded wire and sees "zero" voltage; (aka. "white", aka. "neutral") the other side is "connected" to the hot wire and sees "line" voltage.
(I've used quote marks because there are a few voltage drops here & there and what I said is not literally & precisely true)

When inserting the starter, there will be a moment when only one pin is in contact with the socket.
With one terminal of the starter faulted to its casing, its casing might have been energized with line voltage, or half of line voltage, either of which is hazardous.

The 5 volts you measured is almost certainly the result of voltage drop in the neutral wire. This is entirely normal.
(there's a little bit of voltage drop in the white wire because current's flowing, and no voltage drop in the green wire because no current's flowing)
Were you to remove the starter, turn it 180° and re-insert it, you'd probably see almost line voltage on its casing instead of almost zero volts.
(I am speaking hypothetically. Do not actually try it.)

It's not unusual to get a small shock while standing on a fiberglass ladder. Fiberglass is an insulator, but it's not a perfect insulator, and a little bit of dirt, moisture or capacitance will allow a little bit of current to flow.

If this is in a commercial/institutional/industrial building, it's possible that the fluorescent lamps are powered with 277 volts.

I recommend destroying this starter before disposing of it, to make it impossible for somebody else to repeat this episode.

Did they make "preheat" style systems that operate on 277 volts?

The ballast and one side of the lamp are in series on one side of the "starter" and the other side of the "starter" has just one lamp end in series with a supply conductor. I doubt you would find half the supply voltage at the starter because of different overall impedance on each side of it. But IMO we are both on the right track that the voltage to ground from that starter can vary depending on conditions and can be up to full voltage at times, and with the right conditions, of the supply circuit. I don't know what voltage the lamp is designed to operate at once it has established an arc, but the ballast is going to have whatever difference there is from the input voltage across it. During starting it will be a different voltage because there will be change in overall impedance of the lamp/starter segment of the circuit from what "running" conditions are.

 

[drcampbell]

Did they make "preheat" style systems that operate on 277 volts? ...

I have no idea. I'm not a lamp historian and I never say "never". It's just a generally-applicable caution.

... the ballast is going to have whatever difference there is from the input voltage across it. ...

Um, not quite. The ballast is almost purely inductive and the lamp is not. The vector voltage sum will equal the line voltage, of course, but if you measure each one with a voltmeter, without considering the phase angle, you may find that the two voltages add up to quite a bit more than line voltage.

 

[hbiss]

I'm a little confused. I am reading that the OP is talking about 1 starter in a multiple lamp fixture. The OP stated that at the time of the incident none of the lamps lit until the one starter was replaced. I have never seen a fixture that didn't have one starter per lamp.

Was it 277? I don't know either if there were "preheat" ballasts for 277 but one of the first things the OP should have determined is the operating voltage of the fixture and his maintenance people should have been aware of it if it is indeed 277.

Another thought is that when you insert a starter in a live fixture it will buzz or vibrate as the bi-metallic switch operates. You can feel that with your fingers as you twist it.

For what it's worth, new starters available today have plastic cans.

-Hal

 

[LarryFine]

The ballast, a series inductor, is there as a current limiter, because fluorescents drop impedance as they warm up.

 

[hbiss]

And the inductive kick from the inductance because of the initial on/off action of the starter results in a high voltage, enough to strike the arc within the lamp.

-Hal

 

[kwired]

Um, not quite. The ballast is almost purely inductive and the lamp is not. The vector voltage sum will equal the line voltage, of course, but if you measure each one with a voltmeter, without considering the phase angle, you may find that the two voltages add up to quite a bit more than line voltage.

The ballast, a series inductor, is there as a current limiter, because fluorescents drop impedance as they warm up.

So what voltage does the lamp operate at? Same lamp but with 277 volt supply obviously needs something to reduce voltage to similar level it would operate on with 120 volt supply.

 

[LarryFine]

I believe they only operate at 120v. 277 would require a transformer as part of the ballast.

 

[drcampbell]

So what voltage does the lamp operate at? ...

I made a statistically-significant measurement of one antique T12 fixture. 123 volts on the lamp itself. Magnetic ballast, but without an external starter.

 

[MTW]

From an old Advance troubleshooting guide, for a preheat ballast using starters the minimum open circuit voltage is 176V for a F30T12 or a F40T12 lamp. Then you have the voltage kick from the starter circuit opening.

A Low Power Factor Rapid Start ballast for the same F40T12 lamp has a open circuit voltage of 220V

View attachment Advance-fluorescent-ballast-troubleshooting-guide1.pdf

Another link to a European paper describing the starter function.

And the inductive kick from the inductance because of the initial on/off action of the starter results in a high voltage, enough to strike the arc within the lamp.

-Hal

 

[gar]

180703-0745 EDT

The article

http://www.ecospecifier.com/media/7...stitute - Ballasts for Fluorescent Lights.pdf

referenced by MTW in the previous post is very good. I have read only a portion, but the basics of the operation of a fluorescent light are provided.

.

 

[gar]

180703-1046 EDT

I have limitedly looked at a two bulb rapid start 4 ft fixture.

The open circuit filament voltage is about 4.2 V, open circuit across both bulbs about 280 V. Clearly the ballast is a transformer with several secondaries. Three isolated from each other filament secondaries. Possibly a single high voltage secondary with high leakage inductance, or could have an external inductor.

The voltage across both bulbs at initiation of conduction is about 250 V and drops to about 100 V where I think conduction stops. I only have a two channel scope. These are used in diffrence mode to measure voltage.

.